JP2011197557A - Acoustic device and acoustic signal correction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct an acoustic signal by suitably handling a road noise sound.SOLUTION: As a physical quantity directly relating to the road noise sound, an amount of displacement of air in a tire as a generation source of the road noise sound is acquired which is detected by an air pressure sensor. Successively, a stationary variation extraction unit 142 extracts a stationary variation waveform of the displacement of the air in the tire based upon the acquisition result. Then, an in-cabin noise sound calculation unit 143 previously applies a transfer function to the extracted stationary waveform to calculate an in-cabin noise sound. Further, a correction amount determination unit 144 determines a correction amount for a preprocessed data signal PPD based upon the calculated in-cabin noise sound. Successively, the correction amount determination unit 144 sequentially sends correction processing specification CRC based upon the determined correction amount to a correction processing unit 145.

Description

  The present invention relates to an acoustic device, an acoustic signal correction method, an acoustic signal correction program, and a recording medium on which the acoustic signal correction program is recorded.

  Conventionally, an audio device such as a car stereo device is mounted on many vehicles. By using such an acoustic device, music or the like can be enjoyed in the passenger compartment.

  For such a vehicle-mounted acoustic device, a technique has been proposed for making it possible to listen to reproduced sound output from the acoustic device in response to a change in the form of road noise sound according to a change in the running state of the vehicle. . As such a proposed technique, a technique for correcting an acoustic signal based on the speed of a vehicle that is considered to have a correlation with the aspect of road noise sound and the amount of sound components outside the sound band in the sound collection result in the passenger compartment (Patent Document 1). See).

  There has also been proposed a technique for correcting a road noise sound and correcting an acoustic signal without referring to the sound collection result in the vehicle interior as described above and the speed of the vehicle. For example, in order to perform correction that does not depend on the conversation voice in the vehicle interior, a technique for detecting the vibration of the dashboard in the vehicle interior and correcting the acoustic signal based on the detection result has been proposed (see Patent Document 2). . In addition, a technique for detecting vibration of a vehicle body and correcting an acoustic signal based on the detection result has been proposed (see Patent Document 3) in order to distinguish reproduced sound from a vehicle interior from road noise.

JP 2006-340323 A Japanese Utility Model Publication No. 6-19394 Japanese National Patent Publication No. 10-504946

  The estimation of the road noise sound based on the vehicle speed described in the conventional example 1 described above cannot cope with a change in road noise due to a change in road surface condition that cannot be considered from the vehicle speed. Further, in order to distinguish between the reproduced sound in the vehicle interior and the road noise described in the above-described conventional example 1, estimation of road noise sound based on frequency components (for example, frequency components of several Hz) outside the sound band in the collected sound. Then, it is not guaranteed for each vehicle that this estimation result accurately reflects the voice band component of road noise.

  In addition, in the technologies of the conventional examples 2 and 3 described above, vibrations that are not affected by the conversation sound in the vehicle interior and the reproduced sound are detected. However, since vibrations of the dashboard and the vehicle body are detected, Cannot be detected effectively. As a result, it is difficult to perform accurate correction corresponding to the high-frequency component of road noise.

  For this reason, there is a need for a technique that can appropriately correct an acoustic signal by appropriately responding to components in the entire voice band of road noise sound that is actually generated. Meeting this requirement is one of the problems to be solved by the present invention.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an acoustic device and an acoustic signal correction method capable of correcting an acoustic signal in an appropriate manner with respect to road noise sound. To do.

  The invention according to claim 1 is an acoustic device mounted on a vehicle that travels by rotating a tire on a road, and acquires information on air pressure in the tire detected at a predetermined position of the tire. Means for calculating a change waveform of the air pressure based on the acquired information on the air pressure; and an inside of the vehicle for calculating a road noise waveform in the vehicle based on the calculated change waveform. An acoustic apparatus comprising: a waveform calculating unit; and a correcting unit that corrects an acoustic signal based on the calculated road noise waveform.

  According to a sixth aspect of the present invention, there is provided an acoustic device equipped with a vehicle that travels by rotating the tire on a road, including acquisition means for acquiring information on the air pressure in the tire detected at a predetermined position of the tire. And a change waveform calculating step for calculating a change waveform of the air pressure based on the acquired information on the air pressure; and a method for correcting the inside of the vehicle based on the calculated change waveform. And a correction step of correcting an acoustic signal based on the calculated road noise waveform. A method of correcting an acoustic signal, comprising:

  A seventh aspect of the present invention is an acoustic signal correction program characterized by causing the calculation means to execute the acoustic signal correction method according to the sixth aspect.

  The invention according to claim 8 is a recording medium in which the acoustic signal correction program according to claim 7 is recorded so as to be readable by the calculation means.

1 is a block diagram schematically showing a configuration of an audio device according to an embodiment of the present invention. It is a block diagram which shows the structure of the digital processing part of FIG. It is a figure for demonstrating the extraction waveform by the steady change extraction part of FIG. It is a flowchart for demonstrating the correction amount determination process in the digital processing part of FIG.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. In the following description and drawings, the same elements are denoted by the same reference numerals, and redundant descriptions are omitted.

[Constitution]
FIG. 1 schematically shows the configuration of an acoustic device 100 according to an embodiment. As shown in FIG. 1, the acoustic device 100 is mounted on a vehicle CR. The acoustic device 100 is connected with an air pressure sensor 200 equipped in the vehicle CR.

  The air pressure sensor 200 is a kind of strain gauge attached to a tire of the vehicle CR, and detects a displacement of air inside the tire. For this reason, the air pressure sensor 200 can detect the displacement of the internal air that occurs in response to a change in the deformation position of the tire due to traveling, although the air pressure in the tire is substantially constant on average.

  The acoustic device 100 includes a sound source unit 110 and an air pressure acquisition unit 130 as an acquisition unit. In addition, the acoustic device 100 includes a digital processing unit 140, an analog processing unit 150, and a speaker 160.

  The sound source unit 110 outputs the audio content data signal CTD. The audio content data signal CTD output from the sound source unit 110 in this way is sent to the digital processing unit 140.

  For example, when the audio device 100 is a device that reproduces audio content recorded on a recording medium such as a DVD (Digital Versatile Disk), the sound source unit 110 reads the audio content from the recording medium. Is provided. When the acoustic device 100 is a device that reproduces audio content acquired by receiving broadcast waves, the sound source unit 110 includes content extraction means for extracting audio content from the reception results of broadcast waves. .

  The air pressure acquisition unit 130 receives the measurement signal PRS sent from the air pressure sensor 200. Then, the air pressure acquisition unit 130 converts the measurement signal PRS into a form that can be processed by the digital processing unit 140. The conversion result is periodically sent to the digital processing unit 140 as air pressure data PRD.

  In the present embodiment, the detection harness is engaged with a signal harness that connects the air pressure sensor 200 installed in the vehicle CR and an ECU (Electrical Control Unit) that controls the traveling of the vehicle CR, or from the ECU. The measurement signal PRS is supplied to the air pressure acquisition unit 130 by connecting an output harness drawn out for the add-on vehicle-mounted device.

  The digital processing unit 140 receives the audio content data signal CTD sent from the sound source unit 110 and the air pressure data PRD sent from the air pressure acquisition unit 130. The digital processing unit 140 performs a predetermined process on the audio content data CTD, and then performs correction based on the air pressure data PRD. The correction result is sent to the analog processing unit 150 as a corrected audio data signal CSD. Details of the digital processing unit 140 will be described later.

  The analog processing unit 150 includes an analog-digital conversion unit and a power amplification unit (not shown). The analog processing unit 150 receives the corrected audio data signal CSD sent from the digital processing unit 140. Then, the analog processing unit 150 converts the corrected audio data CSD into an analog signal and then amplifies the power to generate an output sound signal AOS. The output sound signal AOS thus generated is sent to the speaker 160.

  The speaker 160 receives the output audio signal AOS sent from the analog processing unit 150. Then, the speaker 160 outputs the sound toward the vehicle interior according to the output sound signal AOS.

  Next, the digital processing unit 140 described above will be described. As shown in FIG. 2, the digital processing unit 140 includes a pre-processing unit 141, a steady change extraction unit 142 as a change waveform calculation unit, and a vehicle interior noise sound calculation unit 143 as an in-vehicle waveform calculation unit. ing. The digital processing unit 140 includes a correction amount determination unit 144 as a part of the correction unit and a correction processing unit 145 as a part of the correction unit.

  The preceding stage processing unit 141 receives the audio content data signal CTD sent from the sound source unit 110. Then, the pre-processing unit 141 performs an equalizer process, a loudness process, and the like designated by the user via an operation input unit (not shown) on the audio content data signal CTD to generate a pre-process data signal PPD. The preprocessed data signal PPD generated in this way is sent to the correction processing unit 145.

  The steady change extraction unit 142 receives the air pressure data PRD sent from the air pressure acquisition unit 130. Then, the steady change extraction unit 142 extracts a steady change component included in the air pressure data PRD.

  Here, the reason for extracting the steady change component will be described. According to the knowledge obtained by the present inventors from the results of research, there are the following three types of noise sounds generated during the traveling of the vehicle CR.

  The first type of noise sound is a sudden noise sound generated by stepping on a local unevenness on a road or a pebble on the road. With the generation of the first type of noise, the air pressure data PRD suddenly changes greatly. However, the first type of noise sound cannot be predicted, and the correction amount determination process is not in time even if correction corresponding to the first type of noise sound is performed. In most cases, the correction amount cannot be applied to the correction of the acoustic signal in time.

  The second type of noise sound is a noise sound that is generated when the tread pattern of the tire is deformed and the air in the concave portion of the tread pattern is released, and is a noise sound having a relatively high frequency called “shear”. When such a second type of noise is generated, the air pressure data PRD constantly changes. For this reason, it is considered that the generation of the second type of noise sound, that is, the steady road noise sound can be predicted and the corresponding effective correction can be performed on the acoustic signal.

  A third type of noise sound is a cavity resonance sound in a tire generated at a road step or seam. The air pressure data PRD suddenly changes greatly with the generation of the third type noise noise. However, the third type noise sound cannot be predicted in the same manner as the first type noise sound, and even if correction corresponding to the third type noise sound is performed, correction is performed. In most cases, the amount determination process is not in time, and the application of the determined correction amount to the correction of the acoustic signal is not in time.

  Based on the above knowledge of the present inventor, in the present embodiment, the preprocessed data signal PPD corresponding to the above-described second type of noise sound is corrected.

  In order to extract the steady change component of the air pressure data PRD, the steady change extracting unit 142 first performs a differentiation process on the air pressure data PRD which is time series data. Then, when the absolute value of the differential value exceeds the threshold value TH, the steady change extraction unit 142 ignores the air pressure data PRD for a period extending from the time point to the predetermined time ΔT.

  The “threshold value TH” is determined in advance based on experiments, simulations, experiences, and the like from the viewpoint of determining the occurrence of the first or third type of sudden noise noise. The “predetermined time ΔT” is determined in advance based on experiments, simulations, experiences, and the like from the viewpoint of ignoring the first or third type of sudden noise noise.

  On the other hand, except for the period in which the air pressure data PRD is ignored as described above, the steady change extraction unit 142 removes the direct current component included in the air pressure waveform indicated by the air pressure data PRD and the component that can be regarded as the direct current component. . Here, the DC component includes a static pressure component that exists even when the vehicle CR is stopped. In addition, as a component that can be regarded as a direct current component, there is a very gradual increase or decrease component of air pressure that accompanies a temperature increase or decrease in the tire as the vehicle CR travels. In the present embodiment, a low-pass filter process is performed to remove a direct current component and a component that can be regarded as a direct current component.

  As a result of the above two steps, the steady change component in the air pressure data PRD is extracted. That is, the “steady change component” in the present embodiment refers to the sudden change in the air pressure in the tire (the first and third types of noise components described above) from the change in the air pressure in the tire while the vehicle is traveling. ) And a very gentle change component of air pressure (a component that can be regarded as a direct current component in the above-described air pressure waveform), and a change component of air pressure in the tire while the vehicle is running.

  The extraction result by the steady change extraction unit 142 is sent to the vehicle interior noise sound calculation unit 143 as steady change data ECD. The state of extraction of the steady change component from the air pressure data PRD is shown in FIG.

  The vehicle interior noise sound calculation unit 143 receives the steady change data ECD sent from the steady change extraction unit 142. Then, the vehicle interior noise sound calculation unit 143 calculates a vehicle interior noise sound by applying a transfer function to the steady change data ECD. This calculation result is sent to the correction amount determination unit 144 as vehicle interior noise sound data RND.

  In this embodiment, the transfer function used in the vehicle interior noise sound calculation unit 143 is based on the air pressure data PRD and the detection result of the vehicle interior noise sound obtained when an impulse impact is applied to the tire. In advance.

  The correction amount determination unit 144 receives the vehicle interior noise sound data RND sent from the vehicle interior noise sound calculation unit 143. Then, the correction amount determination unit 144 determines a correction amount to be applied to the preprocess data signal PPD based on the vehicle interior noise sound data RND. Note that the correction amount determined by the correction amount determination unit 144 has frequency characteristics.

  Then, the correction amount determination unit 144 generates a correction processing amount designation CRC corresponding to the determined correction amount. The generated correction processing amount designation CRC is sent to the correction processing unit 145.

  The correction processing unit 145 receives the correction processing amount designation CRC sent from the correction amount determination unit 144. Then, the correction processing unit 145 performs correction of the correction processing amount specified by the correction processing amount specifying CRC on the preprocessed data signal PPD, and generates a corrected audio data signal CSD. The corrected audio data signal CSD generated in this way is sent to the analog processing unit 150.

[Operation]
Next, the operation of the acoustic device 100 configured as described above will be described mainly focusing on the correction process for the preprocess signal PPD in the digital processing unit 140.

  It is assumed that the audio content data signal CTD is sent from the sound source unit 110 to the digital processing unit 140. Further, it is assumed that the measurement signal PRS is sent from the air pressure sensor 200 to the air pressure acquisition unit 130, and the air pressure data PRD is sent from the air pressure acquisition unit 130 to the digital processing unit 140. Further, it is assumed that the pre-processing mode for the audio content data signal CTD by the pre-processing unit 141 in the digital processing unit 140 has already been specified.

  In the digital processing unit 140, the pre-processing unit 141 receives the audio content data signal CTD. Receiving the audio content data signal CTD, the pre-processing unit 141 performs pre-processing in a designated manner on the audio content data signal CTD to generate a pre-process data signal PPD. Then, the pre-processing unit 141 sends the generated pre-processing data signal PPD to the correction processing unit 145. A correction amount determination process is executed in parallel with the pre-processing in the pre-processing unit 141.

  In the correction amount determination process, as shown in FIG. 4, first, in step S <b> 11, the steady change extraction unit 142 determines whether or not a new number of air pressure data PRD has been received from the air pressure acquisition unit 130. If the result of this determination is negative (step S11: N), the process of step S11 is repeated. Here, the “predetermined number” is sufficient for the later-described differential processing and DC component cut processing, and from the viewpoint of ensuring the timeliness of the determined correction amount, based on experiments, simulations, experiences, etc. Determined.

  When a predetermined number of air pressure data PRD is newly received from the air pressure acquisition unit 130 and the result of determination in step S11 is affirmative (step S11: Y), the process proceeds to step S12. In step S12, the steady change extraction unit 142 performs a differentiation process on the air pressure data PRD.

  Next, in step S13, the steady change extracting unit 142 determines whether or not the absolute value of the differential value exceeds the threshold value TH. If the result of this determination is negative (step S13: N), the process proceeds to step S14.

  In step S14, the steady change extracting unit 142 performs low-pass filter processing on the air pressure data PRD, and removes a direct current component or a component that can be regarded as a direct current component included in the air pressure waveform indicated by the air pressure data PRD. Then, the steady change extraction unit 142 sends the steady change data ECD obtained in this way to the vehicle interior noise sound calculation unit 143.

  Next, in step S15, the vehicle interior noise sound calculation unit 143 that has received the steady change data ECD calculates (convolves) the vehicle interior noise sound with the steady change data ECD, thereby calculating the vehicle interior noise sound. Then, the vehicle interior noise sound calculation unit 143 sends the calculation result to the correction amount determination unit 144 as vehicle interior noise sound data RND.

  Next, in step S16, the correction amount determination unit 144 that has received the vehicle interior noise sound data RND determines a correction amount to be applied to the preprocessed data signal PPD based on the vehicle interior noise sound data RND. Subsequently, the correction amount determination unit 144 generates a correction processing amount designation CRC corresponding to the determined correction amount. Then, the correction amount determination unit 144 sends the generated correction processing amount designation CRC to the correction processing unit 145. Thereafter, the process returns to step S11.

  If the result of the determination in step S13 is affirmative (step S13: Y), the process proceeds to step S17. In step S17, the steady change extracting unit 142 determines whether or not a predetermined time ΔT has elapsed since the differential value exceeded the threshold value TH.

  If the result of the determination in step S17 is negative (step S17: N), the process of step S17 is repeated. If the predetermined time ΔT elapses from the time when the differential value exceeds the threshold value TH during the repetition of the process of step S17 and the determination result in step S17 becomes affirmative (step S17: Y), the process proceeds to step S11. Return.

  For this reason, the steady change data ECD is not supplied to the vehicle interior noise sound calculation unit 143 in the period from when the differential value exceeds the threshold value TH until the predetermined time ΔT elapses. For this reason, during the said period, calculation of a new vehicle interior noise sound is not performed, and also the correction amount is not newly determined. As a result, the correction processing unit 145 performs correction processing based on the correction amount determined immediately before the start of the period.

  By repeating the processes of steps S11 to S17 as described above, the correction amount corresponding to the tire air pressure detection result is determined. Then, the correction processing amount designation CRC corresponding to the determined correction amount is sequentially sent to the correction processing unit 145.

  Upon receiving the correction processing amount designation CRC based on the correction amount determined as described above, the correction processing unit 145 performs correction of the correction processing amount designated by the correction processing amount designation CRC on the preprocessed data signal PPD, and performs correction. A later audio data signal CSD is generated. The corrected audio data signal CSD generated in this way is sent to the analog processing unit 150.

  Upon receiving the corrected audio data signal CSD, the analog processing unit 150 converts the corrected audio data CSD into an analog signal, power-amplifies it, generates an output sound signal AOS, and sends it to the speaker 160. And the speaker 160 which received the output audio | voice signal AOS outputs an audio | voice toward a vehicle interior according to the output audio | voice signal AOS.

  As described above, in the present embodiment, the displacement amount of the air in the tire that is the generation source of the road noise sound detected by the air pressure sensor 200 is acquired as the physical quantity directly related to the road noise sound. Subsequently, the steady change extraction unit 142 extracts a steady change waveform of the displacement of air in the tire based on the acquisition result. Next, the vehicle interior noise sound calculation unit 143 calculates a vehicle interior noise sound by applying a transfer function obtained in advance to the extracted steady-change waveform.

  Next, the correction amount determination unit 144 determines a correction amount for the preprocessed data signal PPD based on the calculated vehicle interior noise sound. Subsequently, the correction amount determination unit 144 generates a correction processing designation CRC based on the determined correction amount, and sequentially sends the generated correction processing designation CRC to the correction processing unit 145. Then, the correction processing unit 145 that has received the correction processing designation CRC performs correction processing on the preprocessed data signal PPD according to the designated correction processing amount.

  For this reason, after estimating the component which generate | occur | produces regularly among the noise sounds which penetrate | invade into a vehicle interior by driving | running | working of vehicle CR over the whole audio | voice band, it is with respect to the acoustic signal for responding to the estimated noise sound. Correction is performed. Therefore, according to the present embodiment, it is possible to correct the acoustic signal with a simple configuration and appropriately corresponding to the road noise sound.

[Modification of Embodiment]
The present invention is not limited to the above-described embodiment, and various modifications are possible.

  For example, in the above embodiment, it is assumed that the air pressure is detected for one tire, but the air pressure for a plurality of tires is detected, and the vehicle interior noise sound is calculated based on the plurality of detection results. It may be.

  In the above embodiment, the pre-processing unit performs the equalizer processing, the loudness processing, and the like specified by the user in the pre-correction in the correction processing unit. However, these processes are performed in the correction processing unit. You may make it perform in the back | latter stage of correction | amendment.

  In the above embodiment, the air pressure sensor 200 equipped on the vehicle CR is used. However, if the air pressure sensor is not equipped on the vehicle CR, an air pressure sensor is prepared independently. It may be.

  The digital processing unit in the above embodiment is configured as a computer system including a central processing unit (CPU: Central Processor Unit) and a DSP (Digital Signal Processor), and all or part of the functions of the digital processing unit described above It can be realized by executing the program. These programs may be acquired in a form recorded on a portable recording medium such as a CD-ROM or DVD, or may be acquired in a form distributed via a network such as the Internet. Good.

DESCRIPTION OF SYMBOLS 100 ... Acoustic apparatus 130 ... Air pressure acquisition part (acquisition means)
142 ... Steady state change extraction unit (change waveform calculation means)
143 ... Vehicle interior noise sound calculation unit (in-vehicle waveform calculation means)
144: Correction amount determination unit (part of correction means)
145 ... Correction processing unit (part of correction means)

Claims (8)

An acoustic device mounted on a vehicle that travels by rotating a tire on a road,
Obtaining means for obtaining information on the air pressure in the tire detected at a predetermined position of the tire;
Change waveform calculation means for calculating a change waveform of the air pressure based on the acquired air pressure information;
In-vehicle waveform calculation means for calculating a road noise waveform in the vehicle based on the calculated change waveform;
Correction means for correcting an acoustic signal based on the calculated road noise waveform;
An acoustic device comprising: The change waveform calculation means removes a direct current component in the air pressure waveform obtained from the air pressure information, calculates a steady change waveform by removing a waveform of a period of suddenly large change in the air pressure waveform,
The in-vehicle waveform calculating means calculates a steady road noise waveform in the vehicle based on the calculated steady change waveform.
The acoustic device according to claim 1.   The change waveform calculating means suddenly greatly changes in the air pressure waveform by removing a waveform in a period from when the absolute value of the differential value of the air pressure waveform exceeds a predetermined value until a predetermined time elapses. The acoustic apparatus according to claim 2, wherein the waveform of the period is removed.   The said in-vehicle waveform calculation means calculates the said road noise waveform by applying the transfer function calculated | required previously with respect to the said change waveform, The any one of Claims 1-3 characterized by the above-mentioned. The acoustic device described in 1.   The acoustic according to claim 4, wherein the transfer function is obtained in advance by analyzing a sound generated in a vehicle interior of the vehicle corresponding to an impulse-like pressure at a predetermined position of the tire. apparatus. An acoustic signal correction method used in an acoustic device mounted on a vehicle that travels by rotating the tire on a road, comprising acquisition means for acquiring information on air pressure in the tire detected at a predetermined position of the tire There,
A change waveform calculating step for calculating a change waveform of the air pressure based on the acquired air pressure information;
An in-vehicle waveform calculating step of calculating a road noise waveform in the vehicle based on the calculated change waveform;
A correction step of correcting an acoustic signal based on the calculated road noise waveform;
An acoustic signal correction method comprising:   An acoustic signal correction program characterized by causing the calculation means to execute the acoustic signal correction method according to claim 6.   8. A recording medium in which the acoustic signal correction program according to claim 7 is recorded so as to be readable by an arithmetic means.

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