JP2007256527A - Waveform synthesizing apparatus and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technology capable of allowing a driver in a vehicle to hear comfortable engine sounds. <P>SOLUTION: A sound wave segmentation part 1031 segments a waveform signal of a single sound which is a sound generated from one cylinder in one cycle of explosion from a series of waveform signals input from a piezoelectric pickup arranged on a prescribed position of the one cylinder of an engine at time interval T=2/r corresponding to the rotational speed r of the engine which is measured by a rotational speed sensor. The waveform signals segmented by the sound wave segmentation part 1031 are stored in a storage part 107. A reading pulse generation part 1033 generates reading pulses at a time interval of about T/N (N is the number of cylinders). A sound wave reading part 1034 reads out the waveform signals stored in the storage part 107 at timing corresponding to the reading pulses output from the reading pulse generation part 1033 and a mixing part 1038 mixes the waveform signals read out by the sound wave reading part 1034. Consequently, sounds of a multi-cylinder engine are synthesized. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for synthesizing a waveform of an engine sound.

There is a technique for artificially synthesizing engine sounds as sound effects in a car racing simulation game or the like. For example, Patent Documents 1 and 2 disclose a technique of storing a plurality of actual engine sound waveforms in accordance with an operating state such as an engine rotation speed and reading out and reproducing a suitable waveform in accordance with a user operation. Has been.
JP 2000-10576 A JP 2005-128262 A

In Non-Patent Document 1, engine sound is obtained by superimposing a plurality of continuous waveforms of sounds (hereinafter referred to as “single sound”) generated by one explosion in one cylinder of the engine. A technique for artificially synthesizing the above has been proposed.
Osamu Maeda, "Virtual Evaluation Technology for Engine Sound Quality", Journal of the Acoustical Society of Japan, Acoustical Society of Japan, 2003, Vol. 59, No. 5, p. p. 288-293

  Engine sounds often become noise for people around them, and therefore, engines and vehicles that do not emit engine noise as much as possible have been developed. However, in many cases, for the driver of the vehicle, the engine sound enhances the joy of driving, and at the same time is information that plays an important role such as warning that the speed is excessive.

  Therefore, there is a demand for a technique for reducing the engine sound scattered around and at the same time allowing the driver to hear a pleasant engine sound. As a method of solving such a problem, for example, by arranging a microphone in the car and collecting engine sound that can be heard in the car while driving, by amplifying the collected sound with an amplifier and then sounding from the speaker in the car, It may be possible to let the driver hear a louder engine sound compared to the engine sound emitted to the outside.

  However, in the case of the above-described means, not only engine sound but also in-car conversation and road noise are simultaneously amplified, resulting in inconvenience and unnaturalness. Also, a quiet engine sound amplified is not necessarily a comfortable sound for the driver even at a loud volume.

  Therefore, the engine sound is synthesized using the techniques disclosed in Patent Documents 1 and 2 and Non-Patent Document 1 described above, and the synthesized engine sound is generated from the speaker in the vehicle, so that powerful engine sound can be given to the driver. It is possible to tell.

  However, since the techniques disclosed in Patent Documents 1 and 2 and Non-Patent Document 1 synthesize engine sound by processing waveform data of engine sound stored in advance, the synthesized sound is derived from actual engine sound. Deviation and still bring about unnaturalness. Such problems can be solved by storing the actual engine sound waveform in advance according to various rotational speeds, accelerator opening, etc., and calling and using the sound waveform corresponding to the driving state during operation. Is done. However, there is a problem that it is necessary to prepare an enormous number of sound waveforms in order to synthesize realistic engine sounds according to various operating conditions.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a new technique that enables a driver in a vehicle to hear a pleasant engine sound.

  In order to achieve the above object, the present invention provides sound waveform input means for acquiring a sound waveform indicating the sound of an operating engine, rotation data input means for acquiring rotation data indicating the rotation speed of the engine, From the sound waveform acquired by the sound waveform input device, a sound waveform cutting device that cuts out a sound waveform of a time corresponding to the rotation speed as a single sound waveform, a storage device that stores the single sound waveform, and the rotation speed In response, a sound waveform reading means that sequentially reads out the single sound waveform from the storage means at a series of timings that periodically arrive, and a composite waveform obtained by mixing the plurality of single sound waveforms read by the sound waveform reading means. And a synthesized waveform generating means for generating a waveform synthesizer.

  According to such a waveform synthesizer, since the engine sound is synthesized using the sound emitted from the actual engine during driving, the engine sound with the reality corresponding to the driving state is stored without storing the waveform data. can get. In addition, in the process of synthesizing the engine sound, flexible processing for adjusting the acoustic characteristics of the synthesized sound is possible.

  In a preferred aspect, the sound waveform input means obtains a sound waveform indicating a sound generated in response to one explosion in one cylinder of the engine which is a multi-cylinder engine, and the sound waveform reading means is the rotation speed. The single sound waveform is sequentially read out at time intervals obtained by further dividing the time required for one explosion calculated based on the above by a predetermined positive integer.

  According to such a waveform synthesizer, the sound of the multi-cylinder engine is synthesized using the sound emitted from one cylinder of the multi-cylinder engine. At that time, it is also possible to synthesize engine sounds having a number of cylinders different from the number of cylinders of the actual engine.

  In another preferred aspect, the waveform synthesizer includes parameter input means for acquiring a parameter, and the sound waveform input means is a sound generated by one explosion in one cylinder of the engine which is a multi-cylinder engine. The sound waveform reading means obtains a sound waveform indicating the parameter, and calculates the parameter as a time obtained by further dividing the time required for one explosion calculated based on the rotation speed by a predetermined positive integer. The single sound waveform is sequentially read out at time intervals obtained by adding fluctuations according to.

  In another preferred embodiment, the waveform synthesizer includes parameter input means for acquiring parameters, and amplitudes having fluctuations corresponding to the parameters in the plurality of single sound waveforms read out by the sound waveform reading means. Fluctuation adding means for adding expansion or contraction in the direction or time direction, and the synthesized waveform generating means generates a synthesized waveform by mixing the single sound waveform to which fluctuation is added by the fluctuation adding means.

  According to these waveform synthesizers, the degree of conspicuousness of the components of the rotation integer order included in the engine sound to be synthesized can be changed by the parameter.

  In another preferred embodiment, the sound waveform input means includes a first sound waveform indicating a sound emitted from a first part of the engine and a second sound indicating a sound generated by a second part of the engine. The sound waveform cutting means cuts out a first single sound waveform from the first sound waveform, cuts out a second single sound waveform from the second sound waveform, The sound waveform reading means sequentially reads out the first single sound waveform at a first series of timings that periodically arrive according to the rotation speed, and a second that periodically arrives according to the rotation speed. The second single sound waveform is sequentially read at a series of timings, and the combined waveform generation means is configured to read the plurality of first single sound waveforms and the plurality of second single sound waves read by the sound waveform reading means. Mixing the shape To generate a composite waveform.

  According to such a waveform synthesizer, it is possible to perform different processes for adjusting the acoustic characteristics for each of a plurality of sound elements constituting the engine sound.

  In the above preferred embodiment, the first sound waveform indicates a sound generated by the first cylinder of the engine which is a multi-cylinder engine, and the second sound waveform indicates a sound generated by the second cylinder of the engine. May be shown.

  According to such a waveform synthesizer, it is possible to perform different processing for adjusting the acoustic characteristics for each of the plurality of cylinders of the engine sound. In addition, since different sound waveforms are used among the cylinders, it is possible to suppress the degree of conspicuousness of components of the rotational integer order included in the engine sound to be synthesized.

  In the above preferred embodiment, the first sound waveform and the second sound waveform may indicate a sound emitted from any one of a cylinder, an intake pipe, and an exhaust pipe included in the engine.

  According to such a waveform synthesizer, it is possible to perform different processing for adjusting acoustic characteristics for each of the cylinder, the intake pipe, and the exhaust pipe of the engine.

  In another preferred embodiment, the waveform synthesizer includes a parameter input means for acquiring a parameter, a first single sound waveform having a correlation according to the parameter, by performing different processing on the single sound waveform and Sound waveform processing means for generating a second single sound waveform, and the sound wave reading means outputs the first single sound waveform at a first series of timings that periodically arrive according to the rotation speed. In addition to sequentially reading out, the second single sound waveform is sequentially read out at a second series of timings that periodically arrive according to the rotational speed, and the synthesized waveform generating means is read out by the sound waveform reading means A plurality of the first single sound waveforms and a plurality of the second single sound waveforms are mixed to generate a composite waveform.

  According to such a waveform synthesizer, the degree of conspicuousness of the component of the rotation integer order included in the engine sound to be synthesized can be changed by the parameter.

  In another preferred embodiment, the waveform synthesizer includes a parameter input unit that acquires a parameter, and a frequency characteristic that changes a frequency characteristic according to the parameter to the single sound waveform extracted by the sound waveform cutting unit. Characteristic changing means, and the sound waveform reading means sequentially reads the single sound waveform having the frequency characteristic changed by the frequency characteristic changing means.

  According to such a waveform synthesizer, the timbre of the engine sound to be synthesized can be changed by the parameter.

  The present invention also provides a program for causing a computer to execute processing performed by the waveform synthesizer. As a result, the above waveform synthesizer is realized by a computer.

[1. Principle of sound waveform synthesis]
Hereinafter, in order to understand the present invention, the principle of a method of synthesizing sound of a multi-cylinder engine using single sound of a single-cylinder engine (hereinafter referred to as “single sound control reproduction method”) will be described. As an example, a 4-cylinder 4-stroke engine will be described below.

  In the single sound generation control reproduction method, first, a single sound waveform of the engine is prepared. The cylinders of the four-stroke engine are driven by pushing the crankshaft by repeating the four steps of fuel intake, fuel compression, explosion caused by fuel ignition, and exhaust after explosion. Single sound is a sound that is emitted when one cylinder of the engine performs these four steps and one cycle of operation.

  When a single sound waveform is obtained, a sound generated when one cylinder of the engine is continuously operated (hereinafter referred to as “continuous sound”) is synthesized by continuing the single sound waveform. FIG. 1 is a diagram showing how continuous sounds are synthesized. The left diagram of FIG. 1 illustrates a single sound waveform having a maximum amplitude A0 and a time T0 (seconds). In the synthesis of continuous sounds, a single sound waveform that is the original waveform, with the expansion and contraction in the amplitude direction and the time direction, sequentially connected. In addition, in order to reduce noise generated due to discontinuity of the connecting portion, a process of multiplying a window function having zeros at both ends is performed prior to connection.

  In generating a single sound used for synthesizing continuous sounds, a predetermined fluctuation is added to the degree of expansion / contraction applied to each original waveform in order to generate a more natural sound. As a result, the amplitude and time of each single tone constituting the continuous sound are slightly different from each other. The right diagram of FIG. 1 shows a state in which continuous sounds are generated by concatenating eight single sounds, and the amplitude and time of each single sound included in the continuous sounds are sequentially changed to A1 to A8 and T1 to T1 by adding fluctuations. Each is different from T8 (seconds).

  Since the length of the single sound included in the continuous sound synthesized as described above fluctuates around the time T0 of the original waveform, the period of the continuous sound is T0 (seconds), and the fundamental tone is f0 = 1 / T0 ( Hz). In the case of a 4-stroke engine, the crankshaft rotates twice in the four steps of intake, compression, explosion, and exhaust. Therefore, if the engine speed is r (rpm), the cycle T0 = (2 × 60) / r ( Second).

  Subsequently, in order to synthesize the sound of the four-cylinder engine, four continuous sounds obtained by synthesizing as described above, that is, four sounds emitted from one cylinder are superimposed to synthesize a superposed sound. During this superposition, an offset time of T0 / 4 (seconds) is sequentially added to each continuous sound. That is, the start time of the second continuous sound is delayed from the start time of the first continuous sound by T0 / 4 seconds, and the start time of the third continuous sound is delayed from the start time of the second continuous sound by T0 / 4 seconds. The start time of the fourth continuous sound is delayed from the start time of the third continuous sound by T0 / 4 seconds. FIG. 2 is a diagram showing a state in which superposed sounds are synthesized by superposition of continuous sounds.

  In the superposed sound synthesized as described above, substantially the same waveform is repeated every time T0 / 4 (seconds). Accordingly, the cycle of the superposed sound is T = T0 / 4 (seconds), and the fundamental sound is f = f0 × 4 (Hz). The superposed sound synthesized in this way is the sound of a four-cylinder four-stroke engine generated by the single sounding control reproduction method.

[2. Experiment on change of acoustic characteristics of engine sound]
Subsequently, in the process of the inventor of the present application in the process of reaching the present invention, an experiment conducted using the single sound generation control reproduction method and the result are shown below. First, the inventor of the present application finally applied expansion and contraction fluctuations in the amplitude direction and time direction (hereinafter referred to as “amplitude fluctuation” and “time fluctuation”, respectively) added to the single sound of the original waveform in the synthesis of the continuous sound. It was confirmed by experiment how it affects the resulting superposed sound. FIG. 3 is a graph showing the results of the experiment.

  3 (A-1) and 3 (A-2) are obtained in the case where amplitude fluctuation and time fluctuation are not added at all in continuous sound synthesis, that is, in the case where the original waveform is used as it is for continuous sound synthesis. The waveform and frequency characteristics of the superposed sound are shown. 3 (B-1) and 3 (B-2) show the waveform and frequency characteristics of the superimposed sound obtained when only amplitude fluctuation is added and no time fluctuation is added in the synthesis of continuous sound. Show. Further, FIG. 3 (C-1) and FIG. 3 (C-2) show the waveform and frequency characteristics of the superposed sound obtained when both amplitude fluctuation and time fluctuation are added in the synthesis of continuous sound. Yes.

  From FIG. 3, it is confirmed that the difference between the peak and valley of the amplitude in the frequency characteristic of the superposed sound is reduced by adding the amplitude fluctuation and the time fluctuation. The peak of amplitude in the low frequency region of the frequency characteristic corresponds to an integer overtone of the fundamental tone, and the greater the difference between the peak and valley of the amplitude, the higher the pure tone, the so-called clear sound. From this, it was found that the pure tone of the superimposed sound can be changed by adjusting the degree of amplitude fluctuation and time fluctuation applied to the original waveform in the synthesis of continuous sound.

  FIG. 4 is a sonagraph showing the results of another experiment conducted to confirm the effect of the addition of fluctuations on the acoustic characteristics of superposed sound. 4A and 4B, the vertical axis represents frequency, and the horizontal axis represents time. However, in the superposed sound used in the creation of FIGS. 4A and 4B, it gradually increases so as to imitate the engine sound when the rotation speed r increases at a rate of 1000 rotations / second. A continuous sound in which single sounds reduced in the time direction at a reduction rate are connected is superposed. Accordingly, a value obtained by multiplying the value on the horizontal axis in FIGS. 4A and 4B by 1000 corresponds to the engine speed r.

  In the superposed sound used for creating FIG. 4A, neither amplitude fluctuation nor time fluctuation is added during the synthesis of continuous sounds. On the other hand, in the superposed sound used for creating FIG. 4B, amplitude fluctuation is not added, but regular time fluctuation is added. Specifically, the expansion / contraction ratio in the time direction with respect to the original sound waveform constituting the continuous sound used for superposition is 0.9, 1.05, 0.95 and 1 (hereinafter, repeated) in order from the top. It has become.

  In FIG. 4A, the peaks of frequency components lined up almost linearly from the lower left to the upper right of the graph are clearly confirmed. These straight lines appearing in the sonagraph indicate the components of the rotation second order, the rotation fourth order, the rotation sixth order,... From the bottom of the graph, and these straight lines are clear in FIG. It can be seen that the peak of the frequency component of the rotation integer order is sharp. On the other hand, in FIG. 4B, it can be seen that the rotation integer order straight line is not clear compared to that in FIG. 4A, and the peak of the rotation integer order frequency component is not sharp.

  From experience, it is known that the clearer the straight line corresponding to the order obtained by dividing the number of cylinders of the engine by 2, the more impression is given to the listener that the engine is turning smoothly. The order obtained by dividing the number of cylinders by 2 is also called an explosion primary. For example, in the case of a 4-cylinder engine, the primary explosion is the secondary rotation.

  4 (A) and 4 (B), the frequency component of the rotation integer order of the synthesized sound that is finally synthesized is more conspicuous when the fluctuation is given to the single sounding than when the fluctuation is not given. In addition, it can be seen that the primary component of the explosion does not appear remarkably as compared with the other components, and that the listener feels that the sound of the engine does not turn very well.

  Next, the inventor of the present application conducted an experiment to determine what effect will occur on the final synthesized sound when different original waveforms are used for each continuous sound corresponding to each cylinder in the synthesis of continuous sounds. confirmed. FIG. 5 is a sonagraph showing the results of the experiment.

  The scales of the vertical axis and the horizontal axis in FIGS. 5A and 5B are the same as those in FIG. FIG. 5A is the same graph as FIG. 4A and is shown again for comparison with FIG. 5B. In the synthesis of the superimposed sound used in the creation of FIG. 5B, continuous sounds synthesized using original waveforms having the same frequency characteristics but uncorrelated with each other are used as continuous sounds corresponding to each cylinder. Yes.

  Although there are various methods for creating an uncorrelated original waveform having the same frequency characteristics, in the creation of FIG. 5B, a section obtained by cutting out different sections of a noise waveform having a predetermined frequency characteristic is used. It is used as an original waveform corresponding to each cylinder. Such a noise waveform itself is dissimilar to a single sounding of the engine, but after a continuous process and a superposition process, it becomes somewhat similar to the sound of a multi-cylinder engine.

  When FIG. 5B is compared with FIG. 5A, a plurality of straight lines appear between the rotation integer-order straight lines, and as a result, it is difficult to identify which straight line is the rotation integer-order. That is, as in FIG. 4B, it can be seen that the sound of FIG. 5B does not show a frequency component of the rotation integer order as compared with the sound of FIG. 5A. However, unlike FIG. 4B, each straight line in FIG. 5B is clear as in FIG. 5A. For this reason, if the original waveform used to synthesize the synthesized sound is changed for each cylinder, the frequency component of the rotating integer order does not stand out depending on the degree of the correlation, but the acoustic characteristics may differ from those due to the addition of fluctuations. I understand.

  Next, the inventor of the present application confirmed by experiments how changes in the frequency characteristics of the original waveform used to synthesize the superimposed sound have an effect on the frequency characteristics of the finally obtained superimposed sound. FIG. 6 is a graph showing the results of the experiment. FIGS. 6A to 6D show frequency components of single sound having different waveforms and frequency components of superposed sound (engine sound) synthesized using the single sound, respectively. FIG. 6 shows that the valley of the amplitude of the superimposed sound has a strong correlation with the amplitude of the single sound used to generate the superimposed sound. That is, it can be seen that the rough acoustic characteristics of the superimposed sound are determined by the acoustic characteristics of the single sound.

[3. Embodiment]
Subsequently, embodiments of the present invention will be described below. The embodiment of the present invention is a waveform synthesizer that picks up sound accompanying explosion in one cylinder of a multi-cylinder engine and mechanical noise such as a cam chain and synthesizes engine sound using the waveform of those sounds. .

[3.1. Constitution]
FIG. 7 is a block diagram showing a configuration of the waveform synthesis system 1 including the waveform synthesis apparatus 10 according to the embodiment of the present invention. The waveform synthesis system 1 is arranged in an engine room and a vehicle of a vehicle driven by an engine. In the following description, as an example, it is assumed that the waveform synthesis system 1 is arranged in an automobile equipped with a 4-cylinder 4-stroke engine.

  The waveform synthesis system 1 includes a waveform synthesizer 10 that performs engine sound synthesis processing, a cylinder sound pickup group 11 that outputs a waveform of a sound accompanying an engine explosion to the waveform synthesizer 10, and an engine for the waveform synthesizer 10. A mechanical noise pickup group 12 that outputs a mechanical noise waveform associated with the operation of the motor, and a rotation that measures the rotational speed of the crankshaft to the waveform synthesizer 10 and outputs a signal indicating the result (hereinafter referred to as “rotational speed signal”). The speed sensor 13, the valve opening sensor 14 that outputs a signal (hereinafter referred to as “valve opening signal”) at the timing when the intake valve starts to open to the waveform synthesizer 10, and the depression of the accelerator pedal to the waveform synthesizer 10 And an accelerator opening sensor 15 for outputting a signal indicating the degree (hereinafter referred to as “accelerator opening signal”).

  Furthermore, the waveform synthesis system 1 includes an amplifier 16 that amplifies the sound waveform synthesized by the waveform synthesis device 10, a speaker 17 that converts the sound waveform output from the amplifier 16 into sound, and a user's response to the waveform synthesis device 10. An input device 18 that outputs a signal corresponding to an operation and a display 19 that displays a message screen to the user in accordance with drawing data output from the waveform synthesizer 10 are provided.

  The cylinder sound pickup group 11 includes an intake sound pickup 111 that is a piezoelectric sensor disposed on the surface of a first intake pipe that supplies fuel gas to the first cylinder of the engine, and a cylinder surface of the first cylinder. An explosion sound pickup 112 that is a piezoelectric sensor and an exhaust sound pickup 113 that is a piezoelectric sensor disposed on the surface of a first exhaust pipe that exhausts exhaust gas from the cylinder of the first cylinder are included.

  The signal output from the intake sound pickup 111 is a waveform signal indicating the vibration of the first intake pipe, and mainly indicates the intake sound accompanying the operation of the first cylinder. The signal output from the explosion sound pickup 112 is a waveform signal indicating the vibration of the first cylinder, and mainly indicates the explosion sound associated with the operation of the first cylinder. The signal output from the exhaust sound pickup 113 is a waveform signal indicating the vibration of the first exhaust pipe, and mainly indicates the exhaust sound accompanying the operation of the first cylinder.

  While the cylinder sound pickup group 11 is a collection of pickups for generating the waveform signal of the sound generated with the operation of the cylinder as described above, the mechanical noise pickup group 12 is generated with the operation of the entire engine. A collection of pickups for generating a sound waveform signal. In other words, the mechanical noise pickup group 12 includes a cam chain sound pickup 121 that is a piezoelectric sensor disposed on the surface of a gear that drives the cam chain, and a fan belt sound pickup that is a piezoelectric sensor disposed on the surface of the fan belt tensioner. 122 is included.

  The signal output from the cam chain sound pickup 121 mainly indicates mechanical noise accompanying the rotation of the cam chain. The signal output from the fan belt sound pickup 122 mainly indicates mechanical noise accompanying the rotation of the fan belt. Note that the cam chain sound pickup 121 and the fan belt sound pickup 122 are examples of pickups included in the mechanical noise pickup group 12. If the pickup picks up mechanical noise generated during engine operation, the pickups are arranged in other parts. May be included in the mechanical noise pickup group 12.

  The rotation speed sensor 13 includes a light emitter, a light sensor, a counter, and a timer arranged near the crankshaft, and light emitted from the light emitter to the crankshaft is reflected by a reflection mark attached to a predetermined position of the crankshaft. Then, the counter counts the number of times the reflected light is received by the optical sensor, outputs a signal indicating the number of times stored in the counter at the timing when one second is counted by the timer, and sets the counter value to zero. And reset the timer. The output signal is a rotation speed signal that indicates the rotation speed of the crankshaft by the number of rotations per second.

  The valve opening sensor 14 is constituted by a combination of a light emitter and an optical sensor arranged to face each other with the intake valve of the first cylinder, for example, and is slightly opened from the closed state by closing the intake valve. When the irradiated light is detected by the optical sensor, a valve opening signal is output. In the case of a 4-stroke engine, the crankshaft rotates twice in four cycles and one cycle of engine explosion, so the valve opening sensor 14 outputs a valve opening signal once every two rotations of the crankshaft.

  The valve opening sensor 14 is an example of a sensor for detecting which timing of the engine cylinder is in one cycle of four steps, and the waveform synthesis system 1 includes other types of sensors. A sensor may be used instead of the valve opening sensor 14. As such a sensor, for example, a sensor for detecting the opening timing of the exhaust valve, a sensor for detecting the ignition timing of the spark plug, and the like can be considered.

  The accelerator opening sensor 15 is configured by, for example, a combination of a plurality of light emitters and light sensors, and utilizes the fact that light emitted from the light emitter by the accelerator pedal is blocked by the accelerator pedal, and any of the light sensors emits reflected light. It is a mechanism that measures the degree of depression of the accelerator pedal depending on whether light is received. In the following description, it is assumed that the accelerator opening sensor 15 outputs an accelerator opening signal indicating a larger value as the degree of depression of the accelerator pedal increases, and the range thereof is 0-100.

  The accelerator opening sensor 15 is an example of a sensor that measures the driving state of the automobile, and the waveform synthesis system 1 includes other types of sensors, and these sensors are added to the accelerator opening sensor 15, or It may be used instead of the accelerator opening sensor 15. As such a sensor, for example, a vehicle speed sensor, a torque sensor for measuring the torque of the crankshaft, and the like can be considered.

  The speaker 17 is, for example, a combination of a speaker 17R and a speaker 17L disposed on the left and right sides of the front part of the vehicle. In addition, the arrangement position of the speaker 17 is not limited to this, and for example, the speaker 17 may be arranged at two positions in the front-rear position in the vehicle or at four positions on the front-rear, left-right. The amplifier 16 is a combination of an amplifier 16R and an amplifier 16L that output a sound signal to each of the speaker 17R and the speaker 17L.

  The input device 18 and the display 19 are integrated as a liquid crystal display with a touch sensor function, for example, and are arranged on an instrument panel in the vehicle.

  The waveform synthesizer 10 includes a sound waveform input bus 101 that is a bus for receiving sound waveform signals output from the pickups included in the cylinder sound pickup group 11 and the mechanical noise pickup group 12, a rotation speed sensor 13, and a valve opening. A sensor signal input bus 102 that is a bus for receiving sensor signals output from each of the sensor 14 and the accelerator opening sensor 15 and a sound waveform signal output from a pickup included in the cylinder sound pickup group 11 are used. Sound waves output from the order component emphasizing filter 103A, the order component emphasizing filter 103B, the order component emphasizing filter 103C, the order component emphasizing filters 103A to 103C, and the pickups included in the mechanical noise pickup group 12, which are filters for generating a synthesized sound. Shape signal left and right 2 And panning and a mixer 104 for mixing the Yan'neru.

  The waveform synthesizer 10 also includes an order component emphasizing filter 103R and an order component emphasizing filter 103L, which are filters for generating synthesized sound using the left and right channel sound wave signals output from the mixer 104, and an order component emphasizing filter. The transmission characteristic simulation filter 105R and the transmission characteristic simulation filter 105L, which are filters that reflect changes in frequency characteristics accompanying the transmission of sound from the engine room to the vehicle interior in the sound waveform signals output from the 103R and the order component enhancement filter 103L, and the accelerator A dynamic filter 106R that applies filter processing in which parameters continuously change in accordance with the accelerator opening signal output from the opening sensor 15 to the sound waveform signals output from the transfer characteristic simulation filter 105R and the transfer characteristic simulation filter 105L. And dynamic filter 106 It is equipped with a.

  The waveform synthesizer 10 stores in advance parameters for filter processing performed by the transfer characteristic simulation filter 105 and the dynamic filter 106, screen definition data for defining a user interface screen, and the like. A storage unit 107 that temporarily stores various data to be used; a screen generation unit 108 that generates drawing data indicating a user interface screen and the like based on the screen definition data stored in the storage unit 107 and outputs the drawing data to the display 19; A parameter input unit 109 for specifying various parameters input by the user based on a signal received from the input device 18 is provided.

  The order component enhancement filters 103A to 103C and the order component enhancement filters 103R to 103L all have the same configuration and function. Accordingly, when it is not necessary to distinguish between them, the order component emphasis filter 103 is simply referred to below. FIG. 8 is a block diagram showing the configuration of the order component enhancement filter 103.

  The order component emphasizing filter 103 receives a single valve opening signal from the valve opening sensor 14 and receives a single signal from a sound waveform signal received from another component (for example, in the case of the order component emphasizing filter 103A, the intake sound pickup 111). A sound waveform cutout unit 1031 that cuts out one waveform signal indicating sound, and after performing equalizer processing according to parameters input by the user on a single sound waveform signal cut out by the sound wave cutout unit 1031 An equalizer 1032 to be stored in the storage unit 107 is provided.

  In addition, the order component emphasizing filter 103 sequentially generates and outputs a pulse signal having a time interval and an amplitude corresponding to a parameter input by the user, and a pulse signal generated by the read pulse generating unit 1033. A sound waveform reading unit 1034 that reads out a sound waveform signal stored in the storage unit 107 by the equalizer 1032 as a trigger, and a sound waveform signal that is sequentially read out by the sound waveform reading unit 1034 is added with a different noise waveform signal between the sound waveform signals. A correlation changing unit 1035 for changing the correlation of

  Further, the order component enhancement filter 103 expands and contracts each of the sound waveform signals generated by the correlation changing unit 1035 in the amplitude direction and the time direction according to the timing and amplitude of the pulse signal generated by the readout pulse generation unit 1033. Thus, a fluctuation adding unit 1036 for adding amplitude fluctuation and time fluctuation between a series of sound signal waveforms, and a window function process for multiplying the sound waveform signal to which amplitude fluctuation has been added by the fluctuation adding unit 1036 by a window function having zeros at both ends. Unit 1037 and a mixing unit 1038 for mixing sound wave signals sequentially generated by the window function processing unit 1037. The sound signal waveforms mixed by the mixing unit 1038 are sequentially output to other components (for example, the mixer 104 in the case of the order component enhancement filter 103A).

[3.2. Operation]
Next, the operation of the waveform synthesis system 1 will be described. When the user performs an activation operation of the waveform synthesizer 10, the screen generator 108 of the waveform synthesizer 10 reads the screen definition data of the user interface from the storage unit 107, generates screen drawing data, and outputs it to the display 19. To do. As a result, a user interface screen is displayed on the display 19.

  FIG. 9 is a diagram illustrating a user interface screen displayed on the display 19. The user interface screen includes a list box 181 for selecting the number of cylinders, an option button group 182 for selecting whether to change the acoustic characteristics for the sound of each cylinder or the entire engine sound, and the acoustic characteristics. An option button group 183 for selecting a sound target to be changed, a fader group 184 constituting a graphic equalizer, a slider 185 for designating the degree of correlation, a slider 186 for designating the degree of time fluctuation, and an amplitude A slider 187 for designating the degree of fluctuation and a command button 188 for instructing start and end of engine synthesis are included.

  In the list box 181, the user can select the actual number of cylinders of the engine or a different number of cylinders. For example, when the user selects 6 cylinders in the list box 181, the waveform synthesis system 1 synthesizes the sound of the 6 cylinder engine from the actual engine sound by the synthesis process described below, and reproduces the synthesized sound in the vehicle.

  The option button group 182 includes options of “only cylinder sound” and “entire engine sound”. “Cylinder sound only” enables the order component enhancement filters 103 </ b> A to 103 </ b> C and disables the order component enhancement filters 103 </ b> R to 103 </ b> L, and outputs sound waves output from the intake sound pickup 111, the explosion sound pickup 112, and the exhaust sound pickup 113. For each of the signals, this is an option for selecting to adjust the acoustic characteristics by the order component enhancement filter 103. On the other hand, the “whole engine sound” activates the order component emphasizing filters 103R to 103L and invalidates the order component emphasizing filters 103A to 103C, and the sound waveform after the sound emitted from the cylinder and the mechanical noise are mixed in the mixer 104. This is an option for selecting the adjustment of the acoustic characteristics by the order component enhancement filter 103 regarding the signal.

  When “cylinder sound only” is selected in the option button group 182, the option button group 183 has “intake sound”, “ Includes “explosive sound” and “exhaust sound” options. These options correspond to the order component enhancement filters 103A to 103C, respectively. On the other hand, when “whole engine sound” is selected in the option button group 182, the option button group 183 includes “right” and “right” as sounds to be subjected to changes in acoustic characteristics by the fader group 184 and the like shown below. “Left” options are included. These options correspond to the order component enhancement filters 103R to 103L, respectively.

  The user sequentially selects the options shown in the option button group 183 and repeats the operation of operating the fader group 184 and the like. When the user operates the fader group 184 and the like to input various parameters by touching the input device 18, the input device 18 outputs a signal corresponding to the user's operation to the parameter input unit 109 of the waveform synthesizer 10. The parameter input unit 109 identifies the parameter input by the user based on the signal received from the input device 18 and the user interface screen definition data stored in the storage unit 107, and the identified parameter is included in the screen definition data. The attribute value of each object is stored in the storage unit 107. For example, in a state where the user selects “cylinder sound only” in the option button group 182 and “intake sound” in the option button group 183, the knob of the slider 187 is moved to set the degree of correlation “2.8”. In the case of input, “2.8” is stored in the storage unit 107 as the attribute value of the slider 187 corresponding to “intake sound”.

  When the user finishes inputting various parameters displayed on the user interface screen as described above, the user touches the command button 188 to instruct the start of engine sound synthesis. In response to this instruction, the waveform synthesizer 10 starts engine sound synthesis processing and output thereof.

  First, when “only the cylinder sound” is selected in the option button group 182 by the user, the order component emphasizing filters 103 </ b> A to 103 </ b> C receive sound waveform signals from the intake sound pickup 111, the explosion sound pickup 112, and the exhaust sound pickup 113, respectively. The sound waveform signal continuously received and synthesized from the received sound waveform signal is continuously output to the mixer 104. Since the operations of the order component emphasizing filters 103A to 103C are the same except that the extraction timing of the single sound waveform signal is different, the operation of the order component emphasizing filter 103A will be described below as an example.

  In the order component emphasizing filter 103A, the sound waveform cutout unit 1031 always receives the waveform signal of the intake sound from the intake sound pickup 111. In this state, the sound waveform cutout unit 1031 receives a rotation speed signal from the rotation speed sensor 13 every second. Further, the sound wave cut-out section 1031 receives a valve opening signal from the valve opening sensor 14 at the timing when the intake valve of the first cylinder of the engine starts to open.

  Assuming that the rotation speed of the crankshaft indicated by the rotation speed signal is r (rotation / second), the time required for four cycles and one cycle of explosion of the first cylinder is T = 2 / r (second). The sound wave cut-out section 1031 is triggered by the timing when T × (3/4) has elapsed from the timing when the valve opening signal is received, and the sound wave signal having the length T from the sound wave signal received from the intake sound pickup 111 sequentially. Cut out. However, since T changes from time to time due to the change of r, the length of each of the sound wave signals cut out by the sound wave cutout portion 1031 also changes accordingly. The sound waveform signal of length T cut out in this way is a waveform signal indicating the intake sound in single sound.

  The timing at which the sound wave cutout portion 1031 is thus delayed by T × (3/4) from the opening start timing of the intake valve, that is, T × (1/4) earlier than the timing at which the intake valve starts to open next. The extraction of the single sound waveform signal at the timing is located near the end of the single sound waveform signal from which the waveform indicating the characteristic part of the intake sound is extracted if the extraction is started from the opening start timing of the intake valve. This is because the characteristic portion is almost cut by the subsequent processing by the window function processing unit 1037. In order to avoid such an inconvenience, the waveform signal cut-out start timing is shifted from the intake valve opening start timing. Note that the degree to which the waveform signal cut-out start timing is delayed is not limited to T × (3/4), and may be delayed by, for example, T × (7/8).

More specifically, the section of the single sound waveform signal cut out by the sound waveform cutout section 1031 is as follows.
The timing at which the sound wave cutout section 1031 receives the valve opening signal is t _n , t _{n + 1} , t _{n + 2} ,.
The rotation speeds indicated by the rotation speed signal received last at the timing when the sound waveform cutout section 1031 receives the valve opening signal are denoted by r _n , r _{n + 1} , r _{n + 2} ,.
In that case, the start timing of the cut-out single sound, from t + T × (3/4) = t + 3 / (2r), t n + 3 / (2r n), t n + 1 + 3 / (2r n + 1), t n + 2 + 3 / ( 2r _{n + 2} ),.
Accordingly, the following sections of the sound waveform signal received from the intake sound pickup 111 are each cut out as a single sound waveform signal.
t _n + 3 / (2r _n ) to t _{n + 1} + 3 / (2r _{n + 1} ),
t _{n + 1} + 3 / (2r _{n + 1} ) to t _{n + 2} + 3 / (2r _{n + 2} ),
t _{n + 2} + 3 / (2r _{n + 2} ) to t _{n + 3} + 3 / (2r _{n + 3} ),
....

  The sound waveform cutout unit 1031 outputs the single sound waveform signal sequentially cut out as described above to the equalizer 1032. The equalizer 1032 receives a single sound waveform signal received from the sound waveform cutout unit 1031, and the attribute of the fader group 184 corresponding to the parameter group input by the user, that is, the “intake sound” included in the screen definition data on the user interface screen. The frequency characteristics of the single sound waveform signal are changed by amplifying or reducing the amplitude of each frequency band according to the parameter group stored in the storage unit 107 as a value. The equalizer 1032 temporarily stores in the storage unit 107 a single sound waveform signal obtained by changing the frequency characteristics.

  As described above, the single sound waveform signal is sequentially stored in the storage unit 107 by the equalizer 1032 at the time interval T of one cycle, while the read pulse generation unit 1033 has the number of cylinders designated in the list box 181 by the user. If N is N, read pulses are generated at time intervals of about T / N. In the following description, as an example, it is assumed that 6 cylinders are selected in the list box 181 by the user.

The readout pulse generator 1033 continuously receives the rotational speed signal and the valve opening signal from the rotational speed sensor 13 and the valve opening sensor 14, respectively, similarly to the sound waveform cutting unit 1031. The read pulse generation unit 1033 calculates t _n + 3 / (2r _n ) at the timing t _n when the valve opening signal is received. This timing is the read start timing of single sound generation of the intake sound of the first cylinder. Hereinafter, this timing is referred to as “first cylinder timing”.

When the readout pulse generation unit 1033 calculates the first cylinder timing: t _n + 3 / (2r _n ), the number N of cylinders input by the user, that is, the attribute value of the list box 181 included in the screen definition data on the user interface screen Based on the number N of cylinders stored in the storage unit 107, the following (N−1) timings are calculated (where T _n = 2 / r _n ).
t _n + 3 / (2r _n ) + T _n / N = t _n + 3 / (2r _n ) + 2 / (N · r _n ),
t _n + 3 / (2r _n ) + 2T _n / N = t _n + 3 / (2r _n ) + 4 / (N · r _n ),
...
t _n + 3 / (2r _n ) + (N−1) T _n / N = t _n + 3 / (2r _n ) + (2N−2) / (N · r _n ).

Now, since the user selects “6 cylinders” in the list box 181 and N = 6, the above timings are as follows.
t _n + 3 / (2r _n ) + T _n / 6 = t _n + 3 / (2r _n ) + 2 / (6r _n ) = t _n + 11 / (6r _n ),
_{t n + 3 / (2r n} ) + 2T n / 6 = t n + 3 / (2r n) + 4 / (6r n) = t n + 13 / (6r n),
_{t n + 3 / (2r n} ) + 3T n / 6 = t n + 3 / (2r n) + 6 / (6r n) = t n + 15 / (6r n),
_{t n + 3 / (2r n} ) + 4T n / 6 = t n + 3 / (2r n) + 8 / (6r n) = t n + 17 / (6r n),
_{t n + 3 / (2r n} ) + 5T n / 6 = t n + 3 / (2r n) + 10 / (6r n) = t n + 19 / (6r n).

These five timings are readout start timings when the single sound generation of the intake sound of the second cylinder to the sixth cylinder is read without adding time fluctuation. Hereinafter, these timings are referred to as “second cylinder reference timing” to “sixth cylinder reference timing”, respectively. Here, the actual engine is 4-cylinder, based on the actual time T _n of 1 cycle calculated from the rotational speed r _n of the engine, the second to the case of 6-cylinder engine is operating at the same rotational speed The readout start timing of single sound generation of the sixth cylinder is calculated.

  The read pulse generation unit 1033 determines the degree of time fluctuation input by the user with respect to the second to sixth cylinder reference timings calculated as described above, that is, the attribute value of the slider 186 included in the screen definition data of the user interface screen. Is added based on the parameters stored in the storage unit 107.

For example, when the degree of time fluctuation input by the user is “4.3 (%)”, the read pulse generation unit 1033 has a range of −4.3% to 4.3% of the time T _n of one cycle. Five random values that take any of the values are generated, and the generated random values are added to the second to sixth cylinder reference timings, respectively. That is, the read pulse generator 1033 generates random values e ₂ , e ₃ , e ₄ , e ₅ and e ₆ in the range of −0.043T _{n to} 0.043T _n and calculates the following five timings.
t _n + 11 / (6r _n ) + e ₂ ,
t _n + 13 / (6r _n ) + e ₃ ,
t _n + 15 / (6r _n ) + e ₄ ,
t _n + 17 / (6r _n ) + e ₅ ,
_{t n + 19 / (6r n} ) + e 6.

  The five timings calculated as described above are the readout start timings when the single sound of the intake sound of the second to sixth cylinders is actually read out. Hereinafter, these five timings are referred to as “second cylinder timing” to “sixth cylinder timing”, respectively.

Subsequently, the readout pulse generation unit 1033 determines the amplitude based on the parameter stored in the storage unit 107 as the attribute value of the slider 187 included in the screen definition data of the user interface screen, that is, the degree of amplitude fluctuation input by the user. Five random values indicating fluctuations are generated. For example, when the degree of amplitude fluctuation input by the user is “6.9 (%)”, the read pulse generation unit 1033 has a random value E ₂ that takes any value in the range of −0.069 to 0.069. , E ₃ , E ₄ , E ₅ and E ₆ . Then, the read pulse generation unit 1033 calculates the following five numerical values using the generated random number value.
1 + E ₂ ,
1 + E ₃ ,
1 + E ₄ ,
1 + E ₅ ,
1 + E ₆ .

  The five numerical values calculated as described above indicate the expansion / contraction rate in the amplitude direction of single sound generation of the intake sound of the second to sixth cylinders, respectively. The expansion / contraction rate in the amplitude direction with respect to the single sound generation of the intake sound of the first cylinder is 1, and the expansion / contraction is not performed.

  When the readout pulse generation unit 1033 calculates the first to sixth cylinder timings and the expansion / contraction ratio in the amplitude direction corresponding to the first to sixth cylinders as described above, the expansion ratio of the first cylinder is calculated at the first cylinder timing. A pulse signal having an amplitude is generated as a readout pulse signal and output to the sound waveform readout unit 1034. Similarly, the read pulse generation unit 1033 generates a pulse signal having an amplitude of the expansion / contraction ratio of the second cylinder to the sixth cylinder as a read pulse signal from the second cylinder timing to the sixth cylinder timing, and the sound waveform reading unit 1034. Output to.

When the readout pulse generation unit 1033 subsequently receives a valve opening signal at timings t _{n + 1} , t _{n + 2} ,..., The readout pulse generation unit 1033 similarly corresponds to the first to sixth cylinder timings and the first to sixth cylinders. The expansion / contraction rate in the amplitude direction is calculated, and a read pulse signal is generated based on the calculated expansion / contraction rate and output to the sound waveform reading unit 1034 and the fluctuation adding unit 1036.

  FIG. 10 is a graph showing a read pulse output from the read pulse generator 1033. In the graph of FIG. 10, the horizontal axis represents time, and the vertical axis represents amplitude. For the first three read pulses described in the graph, coordinate values indicating the generation timing and amplitude are described, but the description of the fourth and subsequent pulses is omitted because the figure is complicated. As shown in FIG. 10, read pulse generator 1033 outputs a read pulse having an amplitude of approximately 1 at a time interval of approximately T / N. The time interval and amplitude are input by the user. The fluctuation according to the degree of the fluctuation is added.

  When the sound waveform reading unit 1034 sequentially receives the read pulses from the read pulse generation unit 1033 at the timing shown in FIG. 10, the sound waveform signal temporarily stored in the storage unit 107 is read by the equalizer 1032 using the read pulses as a trigger. , And hand it over to the correlation changing unit 1035. The sound waveform signal read out by the sound waveform reading unit 1034 is a waveform signal obtained by adjusting the frequency characteristics to a single sound of the intake sound of the first cylinder.

  The correlation changing unit 1035 always generates (N−1) random number sequences that take any value in the range of −1 to 1. N is the number of cylinders input by the user. That is, in this example, since the user has selected 6 cylinders, the correlation changing unit 1035 generates five random number sequences. In addition, the correlation changing unit 1035 always receives a valve opening signal from the valve opening sensor 14. When the correlation changing unit 1035 receives the sound waveform signal from the sound waveform reading unit 1034, the correlation changing unit 1035 receives the received sound wave based on whether the received timing is closest to the first cylinder timing or the second cylinder reference timing to the sixth cylinder reference timing. It is determined which of the first to sixth cylinders the shape signal corresponds to.

  When the correlation changing unit 1035 determines that the received sound waveform signal corresponds to the first cylinder, the correlation changing unit 1035 delivers the received sound waveform signal to the fluctuation adding unit 1036 without performing any special processing. On the other hand, when the correlation changing unit 1035 determines that the received sound waveform signal corresponds to the second to sixth cylinders, the correlation changing unit 1035 includes the degree of correlation input by the user, that is, the screen definition data on the user interface screen. The received sound waveform signal and the generated random number sequence are mixed at a ratio corresponding to the parameter stored in the storage unit 107 as the attribute value of the slider 185.

  For example, when it is determined that the received sound waveform signal corresponds to the second cylinder and the degree of correlation input by the user is “2.8”, the correlation changing unit 1035 adds the received sound waveform signal to the received sound waveform signal. The product obtained by multiplying (1-0.028) and the product obtained by multiplying the first random number sequence by (maximum amplitude of received sound waveform signal) × (0.028) are mixed. The sound waveform signal generated by the mixing process is a different sound waveform signal having a positive correlation with the sound waveform signal received by the correlation changing unit 1035. Further, the larger the numerical value of the degree of correlation inputted by the user, the smaller the correlation between the sound waveform signals. The correlation changing unit 1035 generates the same sound waveform signal using the second to fifth random number sequences even when the sound waveform signals corresponding to the third to sixth cylinders are received. The correlation changing unit 1035 delivers the generated sound waveform signal to the fluctuation adding unit 1036.

  The fluctuation adding unit 1036 sequentially receives readout pulses (see FIG. 10) from the readout pulse generation unit 1033 and sequentially receives sound signal waveforms from the correlation changing unit 1035. When the processing of the sound waveform reading unit 1034 and the correlation changing unit 1035 is sufficiently fast, the timing at which the fluctuation adding unit 1036 receives the read pulse from the read pulse generating unit 1033 and the timing at which the sound signal waveform starts to be received from the correlation changing unit 1035 are almost the same. The same. Therefore, the fluctuation adding unit 1036 associates the sound waveform signal received from the correlation changing unit 1035 with the read pulse received from the read pulse generating unit 1033 based on the closeness of these timings.

  Subsequently, the fluctuation adding unit 1036 temporarily stores the received amplitude value of the readout pulse and the sound waveform signal in the storage unit 107. After that, the fluctuation adding unit 1036 receives the readout pulse and the sound waveform signal at a time interval of about T / N, but with respect to the temporarily stored sound waveform signal until the subsequent (N-1) th readout pulse is received. Do not process.

For example, when the fluctuation adding unit 1036 receives the read pulse P _k at the timing of t _n + 11 / (6r _n ) + e ₂ and receives the sound waveform signal W _k at the timing near the read pulse P _k , the fluctuation adding unit 1036 then receives t _n + 13 / ( 6r _n ) + e ₃ , t _n + 15 / (6r _n ) + e ₄ ,..., While receiving read pulses P _{k + 1} , P _{k + 2} ,..., P _{k + 5} , nothing in the sound signal waveform W _k Not performed.

Thereafter, when the read pulse P _{k + 6} is received at t _{n + 1} + 11 / (6r _{n + 1} ) + e ′ ₂ , the sound waveform signal W _k is read from the storage unit 107, and a process of adding fluctuation to the read sound waveform signal W _k is performed. Do. However, e ′ ₂ is a random value related to the time fluctuation added by the read pulse generation unit 1033 with respect to the timing of t _{n + 1} + 11 / (6r _{n + 1} ).

The fluctuation adding process will be described in detail. First, the fluctuation adding unit 1036 uses the amplitude value of the read pulse _Pk as the expansion / contraction rate, and expands / contracts the sound waveform signal _Wk in the amplitude direction. Subsequently, the fluctuation adding unit 1036, a read pulse P _k and the time between the read pulse P _{k + 6,} so that the time and is expanded and contracted in the amplitude direction sound waveform signal W _k match, the sound waveform signal W _k Expand and contract in the time direction Since the sound wave signals sequentially generated by the fluctuation adding unit 1036 are expanded in the amplitude direction and the time direction at different expansion / contraction ratios according to the read pulse train received from the read pulse generation unit 1033, the amplitude direction and time as a whole. It will have a fluctuation in the direction. The fluctuation adding unit 1036 sequentially delivers the generated sound signal waveform to the window function processing unit 1037.

  When the window function processing unit 1037 receives the sound waveform signal from the fluctuation adding unit 1036, the received sound signal waveform has the same length as the received sound signal waveform, and the central amplitude in the time direction is 1. Multiply by the window function that the amplitude gradually decreases at both ends in the time direction and the amplitude becomes zero at both ends. As a result, a sound waveform signal having zero amplitude at both ends in the time direction is generated. The window function processing unit 1037 sequentially outputs the generated sound waveform signals to the mixing unit 1038.

  The mixing unit 1038 sequentially receives sound waveform signals having a length of approximately T from the window function processing unit 1037 at a time interval of approximately T × (1/6). The mixing unit 1038 sequentially mixes the received sound wave signal group. The sound waveform signal generated by the mixing of the mixing unit 1038 as a whole indicates the intake sound of a virtual 6-cylinder engine (see FIGS. 1 and 2). The mixing unit 1038 outputs the sound waveform signal generated by the mixing to the mixer 104.

  As described above, the order component emphasizing filter 103A performs various types of processing on the first sound generation sound waveform signal of the first cylinder received from the intake sound pickup 111, and the sound waveform signal of the intake sound generated by the 6-cylinder engine. Are combined and output to the mixer 104.

  The order component enhancement filter 103B performs the same processing as the order component enhancement filter 103A, synthesizes an explosion sound waveform signal generated by the 6-cylinder engine, and outputs it to the mixer 104. However, the order component emphasizing filter 103B receives the waveform signal of the single sound of explosive sound from the explosive sound pickup 112, and therefore, the timing of single sound generation by the sound waveform cutout unit 1031 and the read pulse of the read pulse generation unit 1033. The generation timing is different from the case of the order component enhancement filter 103A in that the generation timing is delayed from the case of the order component enhancement filter 103A by, for example, T × (½).

  Similarly, the order component enhancement filter 103 </ b> C performs processing similar to that of the order component enhancement filter 103 </ b> A, synthesizes the sound waveform signal of the exhaust sound generated by the 6-cylinder engine, and outputs it to the mixer 104. However, the order component emphasizing filter 103C receives the waveform signal of the single sound of the exhaust sound from the exhaust sound pickup 113, and therefore, the timing of single sound generation by the sound waveform cutout unit 1031 and the read pulse of the read pulse generation unit 1033. The generation timing is different from that of the order component enhancement filter 103A in that the generation timing is delayed from the case of the order component enhancement filter 103A by, for example, T × (3/4).

  The mixer 104 receives a sound waveform signal group received from each of the order component enhancement filters 103A to 103C and a series of sound wave signals received from each of the cam chain sound pickup 121 and the fan belt sound pickup 122 included in the mechanical noise pickup group 12. After performing a predetermined panning process, it is distributed to the left and right channels and mixed. The panning ratio is determined, for example, depending on how far each of the intake sound pickup 111 to fan belt sound pickup 122 is displaced from the center position in the left-right direction of the automobile.

  The mixer 104 sequentially outputs the right channel sound waveform signal and the left channel sound waveform signal generated by the mixing to the order component emphasizing filters 103R and 103L, respectively. However, when “only the cylinder sound” is selected in the option button group 182 by the user, the order component emphasizing filters 103R and 103R do nothing with the sound waveform signal received from the mixer 104, and transfer them to the transfer characteristic simulation filter 105R. And L.

  The transfer characteristic simulation filters 105R and L input sound wave signals received from the order component emphasizing filters 103R and 103 to a predetermined transfer function so that the sound generated in the engine room reaches the driver's ear in the vehicle. The resulting frequency characteristic change is reflected in the sound signal waveform received from the order component emphasis filters 103R and 103L.

  More specifically, a coefficient sequence of a transfer function calculated based on an impulse response at the driver's head position in the vehicle with respect to an impulse signal generated at, for example, the center position of the engine room is stored in the storage unit 107 in advance. . The transfer characteristic simulation filter 105 is obtained, for example, by multiplying each coefficient sequence obtained by Fourier-transforming the sound signal waveform received from the order component emphasizing filters 103R and 103 by each coefficient sequence of the stored transfer function. The resulting coefficient sequence is inverse Fourier transformed. The transfer characteristic simulation filters 105R and L output the sound signal waveforms thus generated to the dynamic filters 106R and L, respectively.

  The dynamic filters 106R and L always receive an accelerator opening signal from the accelerator opening sensor 15, and perform a filter process corresponding to the received accelerator opening signal on the sound signal waveform received from the transfer characteristic simulation filters 105R and L. The filter process performed by the dynamic filters 106R and L is, for example, a graphic equalizer process. For the processing of the dynamic filter 106, the storage unit 107 stores in advance correspondence data between the accelerator opening and the amplification factor for each frequency band of the graphic equalizer.

  FIG. 11 is a graph showing correspondence data stored in the storage unit 107. In the case of following the data example of FIG. 11, when the accelerator opening signal indicates 90, the dynamic filter 106 sets the amplitude of the frequency band of the center frequency 63 Hz, 125 Hz,. Amplify to ... The dynamic filters 106R and L output the sound waveform signals subjected to such filter processing to the amplifiers 16R and L, respectively.

  When the amplifiers 16R and L receive the sound signal waveforms from the dynamic filters 106R and L of the waveform synthesizer 10 as described above, the amplifiers 16R and L amplify the received sound waveform signals to the speaker level and output them to the speakers 17R and L, respectively. . The speakers 17R and L convert the sound waveform signals received from the amplifiers 16R and L into sound and generate sound. As a result, the driver can hear the engine sound synthesized by the waveform synthesizer 10.

  The engine sound that can be heard by the driver as described above is a sound having acoustic characteristics corresponding to various parameters input by the user on the user interface screen (see FIG. 9). That is, the user can synthesize engine sounds of any number of cylinders that are the same as or different from the actual number of cylinders by inputting the desired number of cylinders on the user interface screen. In addition, on the user interface screen, the user likes the tone of the engine sound by adjusting the frequency characteristics of the single sound waveform for each of the intake sound, explosion sound and exhaust sound with the graphic equalizer indicated by the fader group 184. Can be adjusted.

  In addition, the user adjusts the degree of the distinction of the sound of the rotation integer order by adjusting the degree of correlation, the degree of time fluctuation and the degree of amplitude for each of the intake sound, explosion sound and exhaust sound on the user interface screen. can do.

  By the way, when the user selects “entire engine sound” in the option button group 182 on the user interface screen, the order component emphasizing filters 103A to 103C receive the sound waveform signals received from the intake sound pickup 111 to the exhaust sound pickup 113, respectively. No processing is performed on them, and they are transferred to the mixer 104 as they are. Therefore, the sound waveform signal obtained by mixing by the mixer 104 is a waveform signal indicating a sound obtained by mixing a series of intake sounds, explosion sounds, exhaust sounds, cam chain sounds, and fan belt sounds.

  The order component enhancement filters 103R and 103 perform the same processing as described above for the order component enhancement filter 103A using the sound waveform signal obtained from the mixer 104 by mixing as described above. It should be noted that the extraction timing of the single sound waveform signal by the order component emphasizing filter 103R and the L sound waveform cutout unit 1031 is any timing as long as the time interval coincides with the time interval at which the valve opening signal is received from the valve opening sensor 14. However, it is desirable to set the timing at which the engine sound is considered to be relatively small, for example, the timing of the compression stage, as the extraction timing so that the characteristic portion of the engine sound is not cut by the window function processing.

  The sound wave signal groups generated by the order component emphasizing filters 103R and L are transferred to the transfer characteristic simulation filters 105R and L, respectively, and then processed by the transfer characteristic simulation filter 105, the dynamic filter 106, and the amplifier 16 described above. After that, the sound is produced from the speakers 17R and L.

  In the case where the order component emphasis filters 103A to 103C are activated and the case where the order component emphasis filters 103R to 103L are activated, in the former case, the processing of single sound extraction and multi-cylinder engine sound synthesis is performed as an intake sound. In the latter case, mixing is performed together with mechanical noise after being performed in each of explosion sound and exhaust sound, whereas in the latter, processing of single sound extraction and synthesis of multi-cylinder engine sound is performed for intake sound, explosion sound, exhaust sound, and mechanical noise. The difference is that it is done after mixing. Therefore, in the former, the acoustic characteristics can be adjusted for each of the intake sound, explosion sound, and exhaust sound, while in the latter, the acoustic characteristics can be adjusted for each of the left and right sounds. Note that both the order component emphasizing filters 103A to 103C and the order component emphasizing filters 103R to 103L may be simultaneously activated so as to have both of these merits.

  As described above, according to the waveform synthesizing system 1, the user can listen to the engine sound having a favorite number of cylinders and frequency characteristics while changing the motor sound according to the driving state while driving the automobile. As a result, the driver can enjoy driving while listening to his favorite engine sound.

[4. Modified example]
The above-described embodiments can be variously modified within the scope of the technical idea of the present invention. Such a modification is shown below.

[4.1. First Modification]
In the embodiment described above, the correlation changing unit 1035 generates a random waveform in order to adjust the correlation between single sound generations corresponding to each cylinder, and generates a single sound waveform signal and a random waveform signal for the first cylinder. A single sound corresponding to the second and subsequent cylinders is generated by mixing with an amplitude ratio corresponding to a parameter input by the user. On the other hand, in the first modification, a single sound having a low correlation is generated using waveform signals obtained from each of a plurality of cylinders of an actual multi-cylinder engine without using a random waveform.

  In the first modification, an intake sound pickup 111, an explosion sound pickup 112, and an exhaust sound pickup 113 are arranged for each cylinder of the multi-cylinder engine. For example, in the case of a four-cylinder engine, intake sound pickups 111a to 111d, explosion sound pickups 112a to 112d, and exhaust sound pickups 113a to 113d (where a to d correspond to the first to fourth cylinders) are predetermined engine settings. The waveform signal is generated at each position.

  Further, in the first modification, since it is necessary to perform the timing of single sound generation based on the opening start timing of the intake valve in each cylinder, the valve opening sensors 14a to 14d are arranged in the vicinity of the intake valve of each cylinder. ing.

  For example, the order component emphasizing filter 103A receives a sound waveform signal indicating the intake sound from each of the intake sound pickups 111a to 111d, and cuts out a single sound waveform signal of the intake sound from each of them. The waveform signals thus cut out are waveform signals different from each other.

When the user selects the same number of cylinders (in this case, four cylinders) as the actual number of cylinders in the list box 181, the correlation changing unit 1035 of the order component emphasizing filter 103 </ b> A selects each cylinder of the engine sound to be synthesized. The following sound waveform signal is used as a single sounding waveform signal corresponding to.
First cylinder of synthesized sound: waveform of the first cylinder of the actual machine,
Second cylinder of synthesized sound: Adjust the waveform of the first cylinder of the actual machine with the waveform of the second cylinder of the actual machine,
Synthetic third cylinder: Adjust the waveform of the first cylinder of the actual machine with the waveform of the third cylinder of the actual machine.
Synthetic fourth cylinder: Adjust the waveform of the first cylinder of the actual machine with the waveform of the fourth cylinder of the actual machine.

  More specifically, for example, the correlation changing unit 1035 is cut out from the sound waveform signal output from each of the intake sound pickup 111a and the intake sound pickup 111b as a waveform signal corresponding to the second cylinder of the engine sound to be synthesized. A single sound waveform is mixed with an amplitude ratio corresponding to a parameter input by the user.

On the other hand, when the number of cylinders different from the actual number of cylinders of the engine is selected by the user in the list box 181, for example, six cylinders, the correlation changing unit 1035 of the order component emphasizing filter 103 </ b> A sets each cylinder of the engine sound to be synthesized. The following sound waveform signals are used as the corresponding single tone waveform signals.
First cylinder of synthesized sound: waveform of the first cylinder of the actual machine,
Second cylinder of synthesized sound: Adjust the waveform of the first cylinder of the actual machine with the waveform of the second cylinder of the actual machine,
Synthetic third cylinder: Adjust the waveform of the first cylinder of the actual machine with the waveforms of the second and third cylinders of the actual machine.
Synthetic fourth cylinder: The waveform of the first cylinder of the actual machine is adjusted with the waveform of the third cylinder of the actual machine.
Synthetic fifth cylinder: Adjust the waveform of the first cylinder of the actual machine with the waveforms of the third and fourth cylinders of the actual machine.
Sixth cylinder of synthesized sound: The waveform of the first cylinder of the actual machine is adjusted with the waveform of the fourth cylinder of the actual machine.

  More specifically, for example, in order to generate a waveform signal corresponding to the third cylinder of the engine sound to be synthesized, for example, the correlation changing unit 1035 first outputs the sound waveform output from each of the intake sound pickup 111b and the intake sound pickup 111c. A single sound waveform cut out from a signal is mixed by expanding and contracting in the amplitude direction with an expansion ratio of 50%. Thereafter, the correlation changing unit 1035 mixes the single sound waveform extracted from the sound waveform signal output from the intake sound pickup 111a and the sound waveform signal generated by mixing with an amplitude ratio corresponding to the parameter input by the user. Is generated as a waveform signal corresponding to the third cylinder of the engine sound to be synthesized.

  In this way, in the first modification, single sound waveform signals having low correlation are generated using the waveform signals obtained from each of the plurality of cylinders, and are used for engine sound synthesis.

[4.2. Second Modification]
Also in the second modified example, as in the first modified example, single sound waveforms having a low correlation are generated without using random waveforms, and these single sound waveforms are used for engine sound synthesis. However, in the first modification, different waveform signals are acquired from each cylinder of the multi-cylinder engine, whereas in the second modification, different sections of the waveform signals acquired from the first cylinder are single sound waves. Cut out as a shape and different single sound waveforms cut out as such are used for engine sound synthesis.

  In the second modification, the intake sound pickup 111, the explosion sound pickup 112, the exhaust sound pickup 113, and the valve opening sensor 14 are arranged only in the first cylinder, as in the above-described embodiment. However, when the time of one cycle is T, the sound waveform cutout unit 1031 does not cut out a single sound waveform signal having a length T at a time interval T, but instead of T × {(N + 1) / N}. A single tone waveform signal of length T is cut out at time intervals.

  FIG. 12 shows that in the second modification, when the user selects four cylinders in the list box 181, the sound waveform cutout unit 1031 generates four single sounds from the sound waveform signal output from the intake sound pickup 111, for example. It is the figure which showed a mode that the waveform signal of this was cut out. Of the single sound waveform signals cut out by the sound waveform cut-out unit 1031, the latest four are stored in the storage unit 107. Accordingly, each of the four waveform signals stored in the storage unit 107 is updated at a time interval of 5T.

The correlation changing unit 1035 of the order component emphasizing filter 103A uses the following sound waveform signal as a single sound waveform signal corresponding to each cylinder of engine sound to be synthesized.
First cylinder of synthesized sound: first waveform cut out from the waveform of the first cylinder of the actual machine,
The second cylinder of the synthesized sound: the first waveform cut out from the waveform of the first cylinder of the actual machine is adjusted with the second waveform cut out from the waveform of the first cylinder of the actual machine,
The third cylinder of the synthesized sound: the first waveform cut out from the waveform of the first cylinder of the actual machine is adjusted with the third waveform cut out from the waveform of the first cylinder of the actual machine,
Synthetic fourth cylinder: The first waveform cut out from the waveform of the first cylinder of the actual machine is adjusted by the fourth waveform cut out from the waveform of the first cylinder of the actual machine.

  More specifically, for example, the correlation changing unit 1035 uses the first single sound waveform extracted from the sound waveform signal output from the intake sound pickup 111 as the waveform signal corresponding to the second cylinder of the engine sound to be synthesized. The second single sound waveform is mixed with an amplitude ratio corresponding to a parameter input by the user.

  As described above, the start timing of the single sound waveform signal cut out by the sound waveform cutout unit 1031 is shifted by the time of T × (1/4) as compared with the actual sound of the engine. Therefore, the second to fourth single tone waveform signals show a low correlation with the first single tone waveform signal, and can be used instead of the random waveform for adjusting the correlation.

[4.3. Third Modification]
In the above-described embodiment, the sound waveform cutout unit 1031 performs a process of cutting a single sound waveform signal from the input sound wave signal every time interval T, where T is the length of one cycle. It was. However, the length T of one cycle hardly varies greatly between adjacent cycles, and the difference is negligibly small especially when the engine speed is large. Therefore, in the third modification, the sound waveform cutout unit 1031 does not cut out the waveform signal at the time interval T, and the waveform is generated at the timing when the value of the rotational speed signal received from the rotational speed sensor 13 changes to a predetermined threshold value or more. Cut out the signal.

  There are various other timings for extracting the waveform signal by the sound waveform cutting unit 1031 such as the timing of arrival at a predetermined time interval and the timing of receiving a predetermined number of valve opening signals from the valve opening sensor 14. However, any method may be employed as long as the waveform signal cut-out process is thinned out.

  According to the third modification, it is possible to reduce the processing of the sound waveform cutout unit 1031 and the equalizer 1032.

[4.4. Fourth Modification]
In the above-described embodiment, the fluctuation adding unit 1036 receives the read pulse from the read pulse generating unit 1033, and after receiving the sound waveform signal from the correlation changing unit 1035, the fluctuation is added until the length T of one cycle elapses. The unit 1036 does not perform processing on the received sound waveform signal. This is because the fluctuation adding unit 1036 expands and contracts in the time direction, and it is necessary to calculate the time from the start timing of a single tone indicated by the sound waveform signal to the start timing of the next single tone of the same cylinder. Because.

  However, the time interval of the read pulses generated by the read pulse generator 1033 is not significantly different from T / N (N is the number of cylinders input by the user), although time fluctuation is added. Therefore, in the fourth modified example, when the fluctuation adding unit 1036 receives the readout pulse without performing the time direction expansion / contraction, it performs only the amplitude direction expansion / contraction on the sound waveform signal received from the correlation changing unit 1035, and immediately The sound waveform signal is output to the window function processing unit 1037.

  According to the fourth modification, the fluctuation adding unit 1036 temporarily stores the sound waveform signal received from the correlation changing unit 1035 in the storage unit 107, and does not need to perform the process of reading again, and the sound waveform signal from the actual engine. The difference between the timing at which the sound is acquired and the timing at which the engine sound is synthesized using the sound waveform signal is reduced.

[4.5. Fifth Modification]
In the embodiment described above, both the valve opening signal output from the valve opening sensor 14 and the rotation speed signal output from the rotation speed sensor 13 are used. However, for example, the valve opening signal is output once per two rotations of the crankshaft. Therefore, in the fifth modification, the waveform synthesis system 1 includes only the valve opening sensor 14, and instead of the rotation speed signal, a numerical value (rotation / second) that is twice the number of valve opening signals received per second is obtained. Used as a rotation speed signal.

  Instead of substituting the rotation speed signal with a valve opening signal, the valve opening signal may be substituted with a rotation speed signal. That is, the time T of one cycle is calculated by T = 2 / r based on the rotation speed r indicated by the rotation speed signal. Therefore, unless considering that the timing of extracting a single sound waveform signal is synchronized with the operation of the cylinder in four steps and one cycle, the sound waveform extracting unit 1031 starts to output a single sound waveform signal at an arbitrary timing. Thereafter, a single sound waveform signal may be cut out every time T calculated from the rotation speed signal.

[4.6. Sixth Modification]
In the above-described embodiment, the waveform synthesizer 10 is assumed to be realized by a combination of dedicated hardware circuits corresponding to each component, but is not limited thereto. That is, in the sixth modification, the waveform synthesis apparatus 10 is realized by causing a general-purpose computer to execute processing according to an application program.

[5. Remarks]
The numerical values shown in the above-described embodiment and its modifications and the calculation methods of those numerical values are examples for explaining the present invention, and the technical scope of the present invention is not limited to these numerical values and calculation methods.

  For example, the order of processing in the waveform synthesis system 1 shown in the above-described embodiment and its modifications can be changed within the scope of the technical idea of the present invention. For example, although the fluctuation adding unit 1036 has been described as performing expansion / contraction in the time direction after expansion / contraction in the amplitude direction, the order may be reversed.

  Further, the read pulse generation unit 1033 generates the read pulse at the timing illustrated in FIG. 10. For example, the read pulse generation unit 1033 outputs timing data indicating the read timing to the sound waveform reading unit 1034 or the like, and the sound waveform read unit 1034 or the like. The sound waveform signal may be read out at a timing according to the timing data.

  In addition, the read pulse generation unit 1033 generates the read pulse at the timing illustrated in FIG. 10. For example, the read pulse generation unit 1033 generates a read pulse that is separated into a different series for each number of cylinders of the engine sound to be generated. The unit 1034 and the like may perform processing for each read pulse series.

  A sensor other than a piezoelectric sensor may be used as the intake sound pickup 111 or the like, or a microphone that collects sound may be used.

It is the figure which showed the principle of the synthesis | combination of the engine sound concerning this invention. It is the figure which showed the principle of the synthesis | combination of the engine sound concerning this invention. It is the graph which showed the influence which the addition of the fluctuation concerning the present invention has on the synthesized sound of the engine. 6 is a sonagraph showing the influence of the addition of fluctuation according to the present invention on the synthesized sound of an engine. It is the graph which showed the influence which the correlation between single sounding used for the synthesis | combination of the engine sound concerning this invention has on the synthetic sound of an engine. It is the graph which showed the influence which the frequency characteristic of the single sound used for the synthesis of the engine sound concerning this invention has on the synthesized sound of the engine. It is the block diagram which showed the structure of the waveform synthesis system concerning embodiment of this invention. It is the block diagram which showed the structure of the order component emphasis filter concerning embodiment of this invention. It is the figure which showed the user interface screen concerning embodiment of this invention. It is the graph which showed the read-out pulse concerning embodiment of this invention. It is the graph which showed the corresponding data which the dynamic filter concerning embodiment of this invention utilizes. It is the figure which showed the cutting-out method of the waveform signal of single sounding concerning the modification of embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Waveform synthesis system, 10 ... Waveform synthesizer, 11 ... Cylinder sound pickup group, 12 ... Mechanical noise pickup group, 13 ... Rotational speed sensor, 14 ... Valve opening sensor, 15 ... Accelerator opening sensor, 16 ... Amplifier, 17 ... Speaker 18 ... Input device 19 ... Display 101 ... Sound wave input bus 102 ... Sensor signal input bus 103 ... Order component emphasis filter 104 ... Mixer 105 ... Transfer characteristic simulation filter 106 ... Dynamic filter 107 DESCRIPTION OF SYMBOLS ... Memory | storage part 108 ... Screen generation part 109 ... Parameter input part 111 ... Intake sound pickup, 112 ... Explosion sound pickup, 113 ... Exhaust sound pickup, 121 ... Cam chain sound pickup, 122 ... Fan belt sound pickup, 1031 ... Sonic shape cutout part, 1032 ... Equalizer, 1033 Read pulse generator, 1034 ... sound waveform reading unit, 1035 ... correlation changing unit, 1036 ... fluctuation adding unit, 1037 ... window function processing unit, 1038 ... mixing unit.

Claims (10)

Sound waveform input means for acquiring a sound waveform indicating the sound of the engine during operation;
Rotation data input means for acquiring rotation data indicating the rotation speed of the engine;
From the sound waveform acquired by the sound waveform input means, sound waveform cutting means for cutting out the sound waveform of the time according to the rotation speed as a single sound waveform,
Storage means for storing the single sound waveform;
A sound waveform reading means for sequentially reading out the single sound waveform from the storage means at a series of timings periodically coming according to the rotation speed;
A waveform synthesizing apparatus comprising: a synthesized waveform generating unit that generates a synthesized waveform by mixing the plurality of single sound waveforms read by the sound waveform reading unit. The sound waveform input means obtains a sound waveform indicating a sound emitted with one explosion in one cylinder of the engine which is a multi-cylinder engine,
The sound waveform reading means sequentially reads the single sound waveform at time intervals obtained by further dividing the time required for the one explosion calculated based on the rotation speed by a predetermined positive integer. The waveform synthesizer according to claim 1, wherein Equipped with parameter input means for acquiring parameters,
The sound waveform input means obtains a sound waveform indicating a sound emitted with one explosion in one cylinder of the engine which is a multi-cylinder engine,
The sound waveform reading means adds a fluctuation corresponding to the parameter to a time obtained by further dividing a time required for the one explosion calculated based on the rotation speed by a predetermined positive integer. The waveform synthesizing apparatus according to claim 1, wherein the single sound waveform is sequentially read out at an obtained time interval. Parameter input means for acquiring parameters;
Fluctuation adding means for adding expansion or contraction in the amplitude direction or time direction having fluctuations according to the parameters to the plurality of single sound waveforms read out by the sound waveform reading means;
The waveform synthesizing apparatus according to claim 1, wherein the synthesized waveform generating unit generates a synthesized waveform by mixing the single sound waveform to which the fluctuation is added by the fluctuation adding unit. The sound waveform input means obtains a first sound waveform indicating a sound emitted from a first part of the engine and a second sound waveform indicating a sound generated by a second part of the engine,
The sound waveform cutting means cuts out a first single sound waveform from the first sound waveform, and also cuts out a second single sound waveform from the second sound waveform,
The sound waveform reading means sequentially reads the first single sound waveform at a first series of timings that periodically arrive according to the rotation speed, and second that periodically arrives according to the rotation speed. Sequentially reading out the second single sound waveform at a series of timings,
The synthesized waveform generating means generates a synthesized waveform by mixing the plurality of first single sound waveforms and the plurality of second single sound waveforms read by the sound waveform reading means. The waveform synthesizer according to claim 1. The first sound waveform indicates a sound generated by the first cylinder of the engine, which is a multi-cylinder engine, and the second sound waveform indicates a sound generated by the second cylinder of the engine. The waveform synthesizer according to claim 5. The waveform synthesizer according to claim 5, wherein the first sound waveform and the second sound waveform indicate a sound emitted from any of a cylinder, an intake pipe, and an exhaust pipe included in the engine. Parameter input means for acquiring parameters;
Sound waveform processing means for generating a first single sound waveform and a second single sound waveform having a correlation according to the parameter by performing different processing on the single sound waveform;
The sound waveform reading means sequentially reads the first single sound waveform at a first series of timings that periodically arrive according to the rotation speed, and second that periodically arrives according to the rotation speed. Sequentially reading out the second single sound waveform at a series of timings,
The synthesized waveform generating means generates a synthesized waveform by mixing the plurality of first single sound waveforms and the plurality of second single sound waveforms read by the sound waveform reading means. The waveform synthesizer according to claim 1. Parameter input means for acquiring parameters;
Frequency characteristic changing means for adding a change in frequency characteristic according to the parameter to the single sound waveform cut out by the sound wave cutting means;
The waveform synthesizing apparatus according to claim 1, wherein the sound waveform reading unit sequentially reads the single sound waveform having the frequency characteristic changed by the frequency characteristic changing unit. On the computer,
Processing to obtain a sound waveform indicating the sound of the engine during operation;
Processing for obtaining rotation data indicating the rotation speed of the engine;
From the acquired sound waveform, processing to cut out the sound waveform of the time according to the rotation speed as a single sound waveform,
Storing the single sound waveform;
A process of sequentially reading out the single sound waveform stored at a series of timings that periodically arrive according to the rotation speed;
A program for executing a process of generating a synthesized waveform by mixing the plurality of read out single sound waveforms.