JP4957168B2 - Engine sound processing device - Google Patents

Description

  The present invention relates to an engine sound processing apparatus that processes engine sound and the like collected in a vehicle and outputs the processed engine sound.

In recent years, there has been a demand for vehicles that emit less engine sound to the outside from the viewpoint of noise prevention. On the other hand, there is also a demand for enjoying powerful engine sounds in the vehicle. Therefore, as technical means for meeting such demands, various engine sound processing apparatuses have been proposed that pick up engine sound with a microphone in a vehicle, process it and output it to the vehicle. For example, Patent Document 1 collects engine sound generated in a vehicle and adjusts the frequency characteristics of the engine sound, such as increasing the volume of a low frequency range according to the driving state, and emits the sound into the vehicle interior. Has proposed. Patent Document 2 proposes a device for adjusting the level of the order component corresponding to the engine rotational speed to the collected engine sound and emitting the sound into the vehicle interior.
Japanese Unexamined Patent Publication No. 2005-134749 Japanese Patent Application Laid-Open No. 2004-74994

  By the way, in some vehicles, pulsations peculiar to the vehicle are added to the sound pressure, and there is a vehicle that generates an engine sound that makes the listener feel a rumble feeling like a roar. The rumble feeling of the engine sound of this type of vehicle varies depending on the structure of the vehicle and the like, but the engine sound with a pleasant rumble feeling appeals to the driver the strength and luxury of the vehicle. The rumble feeling of the engine sound changes according to changes in the driving state such as the accelerator opening and the vehicle speed, and the change in the rumble feeling varies depending on the vehicle. In that sense, the rumble feeling of the engine sound can be said to be the individuality of the vehicle. There are many requests among driving enthusiasts that they want to enjoy an engine sound with a desired rumble feeling that is different from the original engine sound of their own vehicle. However, an engine sound processing apparatus that can provide the driver with engine sound that meets such requirements has not been provided so far.

  The present invention has been made in view of the circumstances described above, and can process the collected engine sound or the reproduced engine sound into an engine sound having a desired rumble feeling and provide it to the driver. An object is to provide a sound processing apparatus.

The present invention relates to an engine sound signal acquisition means for acquiring an engine sound signal by collecting an engine sound generated in a vehicle or reproducing an engine sound waveform from a storage medium at a speed synchronized with the rotation of the engine of the vehicle. Driving state detecting means for detecting a driving state of the vehicle and outputting a driving state parameter, a control unit for generating a modulation signal having a modulation depth determined based on the driving state parameter, and the engine sound Amplitude modulation means for amplitude-modulating the engine sound signal acquired by the signal acquisition means by the modulation signal, and engine sound output means for outputting the engine sound signal subjected to amplitude modulation by the amplitude modulation means as sound in the vehicle Provided is an engine sound processing device characterized by comprising.
According to this invention, amplitude modulation is performed on the acquired engine sound signal at a depth corresponding to the driving state, and an engine sound having a rumble feeling corresponding to the driving state is output into the vehicle.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of an engine sound processing apparatus according to an embodiment of the present invention. This engine sound processing device is a device that processes engine sound picked up by a vehicle and outputs the processed sound to the passenger compartment. In the example shown in FIG. 1, intake sound, engine explosion sound, exhaust sound, mechanical sound and other sounds are selected as components of engine sound, and N microphones 11-k (k = 1 to N) are Each component of the engine sound is arranged at each position where sound can be collected. Each of the microphones 11-k (k = 1 to N) outputs an analog engine sound signal indicating the collected engine sound waveform. The analog engine sound signal output from the microphone 11-k (k = 1 to N) is amplified by the amplifier 12-k (k = 1 to N), and the A / D converter 13-k (k = 1 to N). ). The A / D converter 13-k (k = 1 to N) samples the analog engine sound signal output from each amplifier 12-k (k = 1 to N) with a sampling clock having a predetermined sampling period, A digital engine sound signal DAk (k = 1 to N) is converted and output.

  The signal processing unit 100 is a digital synthesis engine for two left and right channels based on the digital engine sound signal DAk (k = 1 to N) output from the A / D converter 13-k (k = 1 to N). It is a device that executes signal processing for generating sound signals YL and YR. The signal processing unit 100 may be configured by a dedicated electronic circuit, but may be configured by a processor such as a DSP (Digital Signal Processor). The signal processing in the signal processing unit 100 is executed in synchronization with the sampling clock.

  The synthesized engine sound signals YL and YR output from the signal processing unit 100 are converted into analog signals by the D / A converters 151L and 151R, then amplified by the amplifiers 152L and 152R, and left and right as engine sound output means The sound is output from the speakers 153L and 153R into the vehicle interior.

  The signal processing unit 100 is a transfer characteristic simulation filter 101-k (k = 1 to N) as means for generating the synthesized engine sound signals YL and YR based on the digital engine sound signal DAk (k = 1 to N). And an amplitude modulation unit 102-k (k = 1 to N), a mixer 110, filters 121L and 121R, and dynamic filters 122L and 122R. In an aspect in which the signal processing unit 100 is configured by a processor such as a DSP, various filters, amplitude modulation units, and mixers are programs that cause the processor to perform processing as those filters, amplitude modulation units, and mixers.

  The transfer characteristic simulation filter 101-k (k = 1 to N) is a filter prepared for each sound source such as intake sound and engine explosion sound, and transmits the digital engine sound signal DAk (k = 1 to N). Characteristic simulation filter processing and band limitation processing are performed, and output as digital engine sound signals DBk (k = 1 to N), respectively. Here, the transfer characteristic simulation filter process is a filter process that simulates the characteristics of the sound transmission system from the sound source to the driver through the vehicle body for each sound source such as intake sound and engine explosion sound. is there. Further, the band limiting process is a filter process for extracting only the frequency band component of the sound of the sound source for each sound source such as an intake sound and engine explosion sound.

  The amplitude modulation unit 102-k (k = 1 to N) is converted into the digital engine sound signal DBk (k = 1 to N) by the modulation signal m (t, k) (k = 1 to N) given from the control unit 200. Amplitude modulation processing is performed, and a digital engine sound signal DCk (k = 1 to N) is output. A method for generating the modulation signal m (t, k) (k = 1 to N) in the control unit 200 will be described later.

  The mixer 110 mixes the digital engine sound signal DCk (k = 1 to N) output from the amplitude modulation unit 102-k (k = 1 to N) under the control of the control unit 200, and digitalizes the left and right channels. The engine sound signals XL and XR are synthesized. The filters 121L and 121R are filters that remove unnecessary high-frequency components and low-frequency components that are not suitable for output from the speakers 153L and 153R from the output signals XL and XR of the mixer 110 and adjust the frequency characteristics. The dynamic filters 122L and 122R are filters that filter the output signals of the filters 121L and 121R to output the synthesized engine sound signals YL and YR, and are configured to be able to control the frequency-gain characteristics. . In a preferred embodiment, in order to give a force corresponding to the engine speed to the engine sound heard by the driver, when the engine speed per unit time is, for example, around 3000 rpm, the gain in the frequency band around 400 Hz. When the engine speed per unit time is, for example, around 6000 rpm, the gain of the frequency band around 1 kHz is raised, and so on, by the control unit 200, the frequency vs. gain characteristics of the dynamic filters 122L and 122R are increased. Control is performed.

  The control unit 200 is a device that controls the entire engine sound processing apparatus including the control of the signal processing unit 100. The control unit 200 is connected to various sensors for obtaining parameters indicating the driving state of the vehicle, such as an engine rotation sensor 201, a vehicle speed sensor 202, and an accelerator opening sensor 203, a memory 210, and an operation display unit 220. ing. The operation display unit 220 is disposed at a position in front of the driver in the passenger compartment, and a display unit such as a liquid crystal display panel that provides various display information to the driver and a push for receiving commands and information from the driver. It consists of controls such as buttons. The memory 210 stores a plurality of types of control programs used for controlling the signal processing unit 100. These control programs are programs for generating various parameters for controlling signal processing of the signal processing unit 100 based on output signals of various sensors such as the engine rotation sensor 201.

Among the parameters generated by the control unit 200, the modulation signals m (t, k) (k = 1 to N) given to the amplitude modulation unit 102-k (k = 1 to N) described above are characteristic. is there. As illustrated in FIG. 2, the control unit 200 outputs a sine wave having “1” as the maximum amplitude value as the modulation signal m (t, k) (k = 1 to N). This modulation signal m (t, k) is given by the following equation.
m (t, k)
= 1- (h (k) / 2). (Sin (2πf (k) t + θ) +1) (1)
In the above equation (1), f (k) is the modulation frequency of the modulation signal m (t, k), and h (k) is the modulation depth.

In the case of a four-cycle engine, the control unit 200 determines the modulation frequency f (k) (k = 1 to N) from the engine speed r indicated by the output signal of the engine rotation sensor 201 according to the following equation. A period T0 (explosion period) corresponding to the fifth order is calculated.
T0 = (2 × 60) / r (2)

  And the control part 200 calculates the fundamental frequency F0 which is the reciprocal number of the period T0, and makes this fundamental frequency F0 or its integral multiple frequency the modulation frequency f (k) (k = 1-N). Here, the digital engine sound signal DBk (k = 1 to N), which is a target of amplitude modulation, has components corresponding to intake sound, engine explosion sound, and the like, which are components of engine sound, respectively. Each of these components has a spectrum of a fundamental frequency F0 and an overtone frequency that is an integral multiple of the fundamental frequency F0 because it is triggered by engine rotation. When the digital engine sound signal DBk (k = 1 to N) is subjected to amplitude modulation at the modulation frequency f (k) (k = 1 to N) that is the same as or an integral multiple of the fundamental frequency F0, the amplitude is obtained. The digital engine sound signal DCk (k = 1 to N) indicates engine sound with a sense of rumble with enhanced engine vibration.

  Each modulation frequency f (k) (k = 1 to N) may be the same frequency. For example, the modulation frequency f (1) of amplitude modulation of the digital engine sound signal DB1 corresponding to the intake sound is k1 of the fundamental frequency F0. The modulation frequency f (2) of the amplitude modulation of the digital engine sound signal DB2 corresponding to engine explosion sound is doubled to k2 times the fundamental frequency F0. The frequency f (k) (k = 1 to N) may be varied.

  In addition, the control unit 200 determines the operation depth parameters output from the engine rotation sensor 201, the vehicle speed sensor 202, the accelerator opening sensor 203, and the like in order to determine the modulation depth h (k) (k = 1 to N). To monitor. Then, the modulation depth h (k) (k = 1 to N) is calculated based on the operating state parameter or the mode of temporal change thereof. In this case, the modulation depth h (k) (k = 1 to N) may be the same depth between components such as intake sound and engine explosion sound, or may be different between components. Alternatively, for some components, the modulation depth h (k) may be fixed to 0 so that amplitude modulation is not performed.

  Then, the control unit 200 determines the above equation (1) based on the modulation frequency f (k) (k = 1 to N) and the modulation depth h (k) (k = 1 to N) determined in this way. The modulation signal m (t, k) (k = 1 to N) shown in FIG. 2 is generated and supplied to the amplitude modulation unit 102-k (k = 1 to N) of the signal processing unit 100.

  The method of determining each modulation frequency f (k) (k = 1 to N) from the fundamental frequency F0 and the method of determining the modulation depth h (k) (k = 1 to N) from the operating state parameters are described in the memory 210. Different types of control programs stored in The control unit 200 executes a control program designated by the operation of the operation display unit 220 among these control programs, and the modulation signal m (t, k) (k = 1 to N) generated by the execution of the control program. ) And the like are supplied to the signal processing unit 100.

  Next, an example of the operation of the present embodiment will be described with reference to FIGS. FIG. 3 is a graph showing how the vehicle speed changes when a vehicle equipped with the engine sound processing apparatus according to the present embodiment travels in a certain section. FIG. 4 is a graph showing a change in accelerator opening of the vehicle traveling in the same section. FIG. 5 shows the amplitude modulation of the digital engine sound signal DBk (k = 1 to N) determined by the control program when the control unit 200 of the engine sound processing apparatus of the vehicle is executing a control program. It is a graph which shows depth h (k). In this example, there is no difference in the mode of amplitude modulation between the components such as the intake sound and engine explosion sound, the amplitude modulation frequency is the same between the components, and the modulation depth is also the same.

  In this operation example, the control program executed by the control unit 200 calculates the modulation depth h (k) (k = 1 to N) based on the accelerator opening and the vehicle speed. Increases the modulation depth h (k) (k = 1 to N) according to the speed at which the vehicle speed increases (changes in the positive direction), and if the vehicle speed exceeds the threshold, the modulation is performed according to the excess. Depth h (k) (k = 1 to N) is decreased.

Specifically, the control unit 200 calculates the amplitude modulation depth h (k) (k = 1 to N) by the following procedure.
(1) First, the time differential value of the accelerator opening is calculated, and the time differential value is normalized so that the maximum value is about 1.
(2) Next, the time differential value of the accelerator opening is subjected to a low-pass filter process or a weighted moving average calculation process with an appropriate time constant to obtain an envelope of the time differential value of the accelerator opening.
(3) In the envelope of the time differential value of the accelerator opening, the instantaneous value of the envelope is set to 0 in a section having a negative value.
(4) Next, a correction value for the modulation depth is determined according to the vehicle speed. FIG. 6 is a graph showing an example of the correction value of the modulation depth. In this example, when the vehicle speed is less than 30 km / h, the correction value is set to 0, and in a section where the vehicle speed exceeds 30 km / h, the correction value is changed in the negative direction corresponding to the excess.
(5) Next, the sum of the envelope of the time differential value of the accelerator opening obtained in (2) and the correction value obtained in (4) is obtained, and the modulation depth h (k) (k = 1 to N) ). At this time, if the sum is negative, h (k) (k = 1 to N) = 0.

  When the modulation depth h (k) (k = 1 to N) is calculated by such a method, the following change in the rumble feeling of the engine sound is realized.

  First, when the accelerator is stepped on suddenly and the time differential value of the accelerator opening increases when the vehicle speed is low, the modulation depth h (k) (k = 1 to N) increases and is output to the passenger compartment. (For example, in FIGS. 3 to 5, attention is paid to the fact that the depth of modulation increases with respect to the increase in the accelerator opening in the vicinity of time 10 s).

  Next, in a state where the vehicle speed is high, even when the accelerator is depressed and the accelerator opening is increased, the modulation depth h (k) (k = 1 to N) becomes shallow, and the engine sound output to the vehicle interior (For example, in FIGS. 3 to 5, attention is paid to the fact that the modulation depth is 0 even when the accelerator opening is increased in the vicinity of time 30 s).

  As described above, in this operation example, the same relationship as the three-way relationship of the accelerator opening information, the vehicle speed, and the rumble feeling of the engine sound that can be seen during actual vehicle travel can be reproduced.

  As described above, according to the present embodiment, the signal indicating the collected engine sound is output after being subjected to amplitude modulation according to the driving state parameter, so that the engine has a rumble feeling according to the driving state. Sound can be provided to the driver. In the present embodiment, the control unit 200 executes whether or not amplitude modulation is performed for each component such as intake sound and engine explosion sound, and how many times the modulation frequency of the amplitude modulation is set to the fundamental frequency F0. It is determined arbitrarily in the control program to be executed. Therefore, a variety of contents can be generated as a digital engine sound signal having a rumble feeling.

  Although one embodiment of the present invention has been described above, other embodiments are possible for the present invention. For example:

(1) In the above embodiment, amplitude modulation processing is executed in units of each component such as intake sound and engine explosion sound before mixing by the mixer 110, but amplitude modulation is performed on, for example, the filters 121L and 121R downstream of the mixer 110. Processing may be performed and output to a subsequent circuit.

(2) In the above embodiment, whether or not amplitude modulation is performed for each component such as intake sound and engine explosion sound (whether the modulation depth h (k) is a value calculated from the operating state parameter or is fixed to 0). Although the control unit 200 determines in accordance with the control program, an operation element may be provided in front of the driver in the vehicle, and the presence or absence of amplitude modulation for each component may be determined by the operation of the operation element.

(3) In the above embodiment, the control unit 200 determines the depth of amplitude modulation according to the operating state parameter. However, an operation element for specifying the degree of amplitude modulation is provided, and the control unit 200 is specified by this operation element. The amplitude modulation depth may be determined based on the specified value of the degree of amplitude modulation and the operating state parameter (for example, by multiplication of both).

(4) The driving state parameter used for controlling the amplitude modulation depth may be specified by the driver by operating the operator. For example, an operator for designating various operation state parameters such as a vehicle speed, an accelerator opening degree, and an engine speed is provided in the vehicle. For example, when the driver turns on each operation element that specifies the vehicle speed and the accelerator opening, the control unit 200 sets the vehicle speed and the accelerator opening as independent variables from various functions stored in the memory 210 in advance. Then, a function having the amplitude modulation depth as a dependent variable is selected, and this function is used to control the amplitude modulation depth.

(5) In the above embodiment, a sinusoidal modulation signal is used. However, a periodic waveform signal other than a sine wave such as a rectangular wave or a triangular wave may be used as the modulation signal. Alternatively, the waveform of the modulation signal may be varied between components such as intake sound and engine explosion sound. Or you may comprise so that a driver | operator can select the waveform of a modulation signal for every component.

(6) The signal processing unit 100 may be configured by an analog circuit, and the A / D converter 13-k (k = 1 to N) and the D / A converters 151L and 151R may be deleted.

(7) In the above embodiment, the fundamental frequency F0 is obtained based on the engine speed detected by the engine revolution sensor 201. However, even if the fundamental frequency F0 is detected from a signal waveform such as engine explosion sound to be collected. Good.

(8) In the above embodiment, the modulation frequency f (k) is a frequency that is an integer multiple of the fundamental frequency F0, but the modulation frequency f (k) may be a frequency that is a non-integer multiple of the fundamental frequency F0.

(9) In the above embodiment, the engine sound is picked up, processed and reproduced from the speaker. However, instead of actually collecting the engine sound in this way, the engine sound waveform data is stored in the memory in advance, and the waveform data is read from the memory at a reading speed corresponding to the engine speed, and the pseudo engine sound signal is read. , And the signal processing similar to that in the above embodiment may be performed on the pseudo engine sound signal.

It is a block diagram which shows the structure of the engine sound processing apparatus which is one Embodiment of this invention. It is a figure which illustrates the waveform of the modulation signal in the embodiment. It is a graph which shows the mode of the change of the vehicle speed of the vehicle in the operation example of the embodiment. It is a graph which shows the mode of the change of the throttle opening of the vehicle in the operation example. It is a graph which shows the mode of the change of the modulation depth in the same operation example. It is a graph which shows the example of the correction value of the modulation depth in the same operation example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 200 ... Control part, 210 ... Memory, 220 ... Operation display part, 201 ... Engine rotation sensor, 202 ... Vehicle speed sensor, 203 ... Accelerator opening degree sensor, 11-k (k = 1-N) ... ... Microphone, 12-k (k = 1 to N) ... Amplifier, 13-k (k = 1 to N) ... A / D converter, 100 ... Signal processing unit, 151L, 151R ... D / A Converter, 152L, 152R... Amplifier, 153L, 153R... Speaker, 101-k (k = 1 to N)... Transfer characteristic simulation filter, 102-k (k = 1 to N). 110: mixer, 121L, 121R: filter, 122L, 122R: dynamic filter.

Claims (2)

Engine sound signal acquisition means for acquiring an engine sound signal by collecting engine sound generated in the vehicle or reproducing an engine sound waveform from a storage medium at a speed synchronized with the rotation of the engine of the vehicle;
Means for detecting the driving state of the vehicle and outputting driving state parameters, the driving state detecting means including means for detecting the engine speed, the vehicle speed, and the accelerator opening, respectively, as the driving state; ,
A means for generating a modulation signal having a modulation depth determined based on the driving state parameter and a frequency determined based on the engine speed , wherein the accelerator opening of the vehicle is in a positive direction. A control unit that increases the depth of modulation according to a changing speed, and decreases the depth of modulation according to the excess when the vehicle speed of the vehicle exceeds a threshold ;
An amplitude modulation means for amplitude-modulating the engine sound signal acquired by the engine sound signal acquisition means with the modulation signal;
Engine sound processing means, comprising: engine sound output means for outputting an engine sound signal subjected to amplitude modulation by the amplitude modulation means as sound into the vehicle. The engine sound signal acquisition means includes a plurality of sound collection units that collect sound that is one component of engine sound in each part of the vehicle and output a signal indicating the collected sound,
The control unit outputs the modulation signal individually for each output signal of the plurality of sound collection units,
2. The amplitude modulation unit according to claim 1, wherein the amplitude modulation unit performs amplitude modulation on each output signal of the plurality of sound pickup units using a modulation signal individually output for each output signal. Engine sound processing device.

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