JP2022143855A - Speaker distortion correction device and speaker unit - Google Patents

Abstract

To provide a speaker distortion correction device and speaker unit for correcting a distortion of an output of a speaker with a comparatively simple configuration.SOLUTION: An input signal Si to be output by an audio device 5 is input to a linear reverse filter 42 as an intermediate correction signal Sm through a non-linear correction filter 41. An output of the linear reverse filter 42 is output to a speaker 2 as an output signal So. Transmission characteristics (filter coefficient) of the non-linear correction filter 41 are set to the transmission characteristics to cancel a distortion due to non-linear characteristics of the speaker 2. An adaptive algorithm execution section 43 allows a difference between a vibration of the speaker 2 without a distortion with respect to the input signal Si and an actual vibration of the speaker 2 indicated by the output of a sensor 3 to be an error, so as to adaptively update the filter coefficient of the linear reverse filter 42.SELECTED DRAWING: Figure 1

Description

The present invention relates to technology for correcting distortion of speaker output with respect to input.

Equivalent circuits of various speakers and techniques for controlling driving of the speakers based on the equivalent circuits are known (Non-Patent Document 1, Patent Document 1).
In addition, as a technology for controlling speaker driving based on an equivalent circuit, there is also a technology for correcting an audio signal that drives a speaker so that the distortion of the speaker output with respect to the input is eliminated based on the equivalent circuit of the speaker. It is known (patent document 2).

Also known is a motional feedback technique that includes a sensor for detecting vibration of the diaphragm of the speaker and controls driving of the speaker according to the vibration detected by the sensor (for example, Patent Documents 3 and 4).

WO2017/179539 Japanese Patent No. 6522668 Japanese Unexamined Patent Application Publication No. 2008228214 Japanese Unexamined Patent Application Publication No. 2010124026

Klippel, Wolfgang, "Modeling the large signal behavior of micro-speakers", 133rd Audio Engineering Society Convention 2012, Paper Number 8749, October 25, 2012

It is conceivable to use motional feedback technology to detect the vibration of the diaphragm of the speaker and correct the audio signal that drives the speaker according to the detected vibration so that the distortion of the speaker is eliminated.

In this case, the adaptive filter is applied to the correction of the audio signal, the difference between the ideal vibration and the detected vibration is regarded as an error, and the coefficient of the adaptive filter is updated so that the error is minimized. Distortion can be eliminated.

On the other hand, speaker characteristics include linear characteristics and nonlinear characteristics.
For example, in the speaker equivalent circuit shown in FIG. 4, Bl, KMS, Le(x,i), etc. exhibit nonlinear characteristics.
The equivalent circuit in FIG. 4 is the equivalent circuit shown in Non-Patent Document 1 above,
Re;Electrical Resistance
Le(x,i);Electrical Inductance
Bl(x);
Fm(x,i);
Mms; Mechanical mass
Rms(v);
Kms(x); Stiffness
is.

If an adaptive filter is configured to cope with such non-linear characteristics of a speaker, the processing and configuration of the adaptive filter will be large-scaled, resulting in an increase in cost.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to correct the distortion of the output of a speaker with a relatively simple configuration while using an adaptive filter.

In order to achieve the above object, the present invention provides a speaker distortion correcting device for correcting the distortion of the output of a speaker with respect to an input signal, a sensor for detecting vibration of the vibration system of the speaker, and the input signal. A non-linear correction filter, a linear inverse filter that receives the output of the non-linear correction filter and outputs an output signal for driving the speaker, and a predetermined adaptive algorithm are executed, and the vibration detected by the sensor is and an adaptive algorithm execution unit that updates the transfer characteristics of the linear inverse filter so that the input signal is oscillated without distortion, and the nonlinear part correction filter is adapted to the nonlinear characteristics of the speaker. It sets a transfer characteristic that corrects the distortion of the output with respect to the input signal.

According to the configuration of the speaker distortion correction device, the distortion due to the nonlinear characteristics of the speaker is handled by the nonlinear part correction filter. can be configured to deal only with distortion due to the linear characteristics of

Therefore, while using the adaptive filter, it is possible to correct the distortion of the output of the speaker, including the distortion due to the non-linear characteristics of the speaker, with a relatively simple configuration.
Further, in order to achieve the above object, the present invention provides a speaker distortion correction device for correcting distortion of the output of a speaker with respect to an input signal, a non-linear portion correction filter that receives the input signal, and the non-linear portion correction filter. and a linear inverse filter for outputting an output signal for driving the speaker, wherein the nonlinear part correction filter corrects the distortion of the output of the speaker with respect to the input signal due to the nonlinear characteristics of the speaker. and the linear inverse filter is set with a transfer characteristic for correcting the distortion of the output of the speaker with respect to the input signal due to the linear characteristic of the speaker.

Here, the transfer characteristic of the linear inverse filter of such a speaker distortion correction device can be adaptively set in advance by adding the above-described sensor and adaptive algorithm execution unit when setting the transfer characteristic. .
Therefore, even with such a speaker distortion correcting device, it is possible to correct speaker distortion with a relatively simple configuration while using an adaptive filter.
Here, the speaker distortion correcting device includes an environment detection means for detecting at least one of the ambient temperature and the aging time of the speaker as an environment, and switching control means for switching to a transfer characteristic suitable for the nonlinear characteristic of the speaker estimated from the environment detected by the speaker.

Alternatively, the speaker distortion correcting device may include a measuring means for measuring the nonlinear characteristics of the speaker, and a transfer characteristic of the nonlinear part correction filter adapted to the nonlinear characteristic of the speaker measured by the measuring means. A switching control means for switching to the characteristic may be provided.

According to the speaker distortion correcting device having these switching control means, when the nonlinear characteristic of the speaker changes, the transfer characteristic of the nonlinear portion correction filter is adjusted to the current nonlinear characteristic of the speaker. can be updated to the transfer characteristic.

Here, the speaker distortion correcting device having the switching control means as described above is provided with state detection means for detecting the state of the audio device that reproduces the audio signal and outputs it as the input signal, and the switching control means switching the transfer characteristic of the non-linear part correction filter at predetermined timings, and changing the predetermined timings to the timing when the audio device is activated and the timing when the audio device is not reproducing a significant audio signal; The timing may include at least one of the timing at which the audio device changes the output level of the input signal and the timing at which the sound source of the audio signal to be reproduced is switched.

The present invention also provides a speaker unit including a speaker distortion correction device and the speaker in a form in which the distortion correction device and the speaker are integrated.

As described above, according to the present invention, speaker distortion can be corrected with a relatively simple configuration while using an adaptive filter.

1 is a diagram showing the configuration of an acoustic system according to an embodiment of the present invention; FIG. 4 is a flowchart showing correction characteristic control processing according to the embodiment of the present invention; It is a figure which shows the other structural example of the acoustic system which concerns on embodiment of this invention. FIG. 3 is a diagram showing an example of an equivalent circuit of a speaker;

Hereinafter, embodiments of the present invention will be described by taking an example of application to an audio system mounted on an automobile.
FIG. 1 shows the configuration of an acoustic system according to the embodiment.
As shown in the figure, the acoustic system includes a correction characteristic control unit 1, a speaker 2, a sensor 3 that detects vibration/displacement of the vibration system of the speaker 2, and an output signal So that is an audio signal for driving the speaker 2. and an audio device 5 for outputting an input signal Si, which is an audio signal.

Then, the correction device 4 corrects the input signal Si output from the audio device 5 and outputs it to the speaker 2 as an output signal So.
Information such as the temperature of the passenger compartment and the elapsed time of the sound system (year of manufacture, current time, etc.) is input to the correction characteristic control unit 1 as external information. Further, the correction characteristics control unit 1 receives from the audio device 5 information on the playback state such as song playback/non-playback, audio source (radio/CD, etc.) outputting the input signal Si, output level, and so on. Information such as (volume, etc.) is input.

Next, the correction device 4 includes a nonlinear part correction filter 41 , a linear inverse filter 42 , an adaptive algorithm execution part 43 and an error calculation part 44 .
An input signal Si output from the audio device 5 passes through the nonlinear part correction filter 41 and is input to the linear inverse filter 42 as the intermediate correction signal Sm, and the output of the linear inverse filter 42 is output to the speaker 2 as the output signal So. .

The transfer characteristic (filter coefficient) of the nonlinear part correction filter 41 can be switched from the correction characteristic control unit 1, and the correction characteristic control part 1 changes the transfer characteristic of the nonlinear part correction filter 41 to the intermediate A transfer characteristic that cancels the distortion of the output of the speaker 2 due to the nonlinear characteristics of the speaker 2 with respect to the input signal Si when the speaker 2 is driven by the correction signal Sm, that is, the transfer characteristic that corrects the distortion due to the nonlinear characteristics of the speaker 2 set to

The error calculator 44 calculates the difference between the vibration of the speaker 2 without distortion with respect to the input signal Si and the actual vibration of the speaker 2 indicated by the output of the sensor 3 .
The adaptive algorithm execution unit 43 and the linear inverse filter 42 constitute an adaptive filter. update the transfer characteristics (filter coefficients) of the linear inverse filter 42 such as an FIR filter so as to minimize the error e.

As a result of this update, the linear inverse filter 42 is set with a transfer characteristic that corrects the distortion of the output of the speaker 2 with respect to the input signal Si due to the linear characteristic of the speaker 2 .
Next, a description will be given of a correction characteristic control process that the correction characteristic control section 1 starts when the acoustic system is activated in order to switch the transfer characteristic of the nonlinear part correction filter 41. FIG.
FIG. 2 shows the procedure of this correction characteristic control process.
As shown in the figure, when the sound system is activated, the correction characteristic control process first starts with the environment such as the temperature of the vehicle compartment indicated by the external information, the aging time of the sound system, the output level of the audio device 5, and the like. (step 202).

On the other hand, if the change is greater than the predetermined level, the current nonlinear characteristics of the speaker 2 are estimated (step 204).
For this estimation, the nonlinear characteristics of each combination of the temperature of the passenger compartment, the aging time of the sound system, and the output level of the audio equipment are obtained in advance and stored as a library. is estimated as the current nonlinear characteristic of the speaker 2 .

Alternatively, this estimation may be performed by measuring the behavior of the speaker 2 and calculating the current non-linear characteristics of the speaker 2 from the measured values.
For example, Kms(x); Stiffness of the equivalent circuit of the speaker 2 shown in FIG. 4 can be calculated as follows based on the measured values.
That is, while outputting an appropriate output signal So such as a test signal, music signal, or acoustic watermark signal to the speaker 2, the current i flowing through the speaker 2 and the input voltage u of the speaker 2 are measured, and the measured current i and the input voltage From u, the resonance frequency fs of the impedance Z=u/i of the speaker 2 is detected. Then, using Mms; Mechanical mass,
Kms(x)=(2πfs) ² Mms
is calculated, the relationship between the displacement x of the vibration system of the speaker 2 output by the sensor 3 and Kms(x) is obtained, and the nonlinear characteristics of Kms(x) are calculated according to the obtained relationship. Here, the nonlinear characteristic of Kms(x) is calculated by preparing a plurality of patterns of the nonlinear characteristic of Kms(x) in advance, and selecting a pattern that matches the relationship between the obtained displacement x and Kms(x). (x) may be calculated as a non-linear characteristic.

Then, the transfer characteristic of the nonlinear portion correction filter 41 is switched to the transfer characteristic corresponding to the estimated current nonlinear characteristic of the speaker 2 (step 206), and the process proceeds to step 208. FIG. A transfer characteristic corresponding to a nonlinear characteristic is a transfer characteristic that corrects distortion due to the nonlinear characteristic, and in step 206, the corresponding transfer characteristic may be calculated using a speaker model that reflects the estimated nonlinear characteristic. Alternatively, the transfer characteristic corresponding to each nonlinear characteristic may be obtained and stored in advance, and the transfer characteristic corresponding to the estimated nonlinear characteristic may be obtained as the transfer characteristic corresponding to the current nonlinear characteristic of the speaker 2 .

Alternatively, for each combination of the temperature of the passenger compartment, the aging time of the sound system, and the output level of the audio device, the transfer characteristics corresponding to the nonlinear characteristics for each combination are obtained in advance and stored as a library. In step 206, the transfer function corresponding to the current environment is selected from the library as the transfer characteristic corresponding to the current nonlinear characteristic of the speaker 2, and the transfer characteristic of the nonlinear portion correction filter 41 is switched to the selected transfer characteristic. can be

Now, if the process proceeds from step 202 or step 206 to step 208 as described above, the correcting device 4 outputs the output signal So obtained by correcting the input signal Si from the audio device 5 to the speaker 2. start the output.

Then, the estimation of the current nonlinear characteristics of the speaker 2 described above (step 210) is repeated until the update timing arrives (step 212).
Here, the detection of the update timing includes the timing at which the audio device 5 finishes reproducing the music, the timing at which the audio source outputting the input signal Si by the audio device 5 is switched, and the output level (volume) of the audio device 5. etc.) is detected as update timing based on the information from the audio device 5 .

Then, when the update timing arrives (step 212), it is determined whether or not the transfer characteristic of the nonlinear part correction filter 41 needs to be switched (step 214). Here, in step 214, if the transfer characteristic corresponding to the current nonlinear characteristic of the speaker 2 is different from the transfer characteristic currently set in the nonlinear part correction filter 41, it is necessary to switch the transfer characteristic of the linear part correction filter. It is determined that

On the other hand, when it is determined that it is necessary to switch the transfer characteristic of the nonlinear part correction filter 41 (step 214), the output of the correction device 4 to the speaker 2 is muted (step 216), and the current nonlinear characteristic of the speaker 2 is changed. The transfer characteristic of the nonlinear portion correction filter 41 is switched to the corresponding transfer characteristic (step 218).

Then, the muting of the output to the speaker 2 is canceled (step 220), and the processing from step 210 is returned to.
The correction characteristic control processing performed by the correction characteristic control section 1 has been described above.
By the way, in the above embodiment, one or both of the nonlinear portion correction filter 41 and the linear inverse filter 42 may be applied as filters with fixed transfer characteristics (filter coefficients).

FIG. 3a shows the configuration of an acoustic system in which both the nonlinear part correction filter 41 and the linear inverse filter 42 are filters with fixed transfer characteristics. The calculator 44 and the correction characteristic controller 1 do not need to be provided.

However, in this case, the transfer characteristic fixedly set in the linear inverse filter 42 is set so that the error e is minimized in the configuration in which the sensor 3, the adaptive algorithm execution unit 43, and the error calculation unit 44 shown in FIG. 3b are provided in advance. The transfer characteristic is adapted to Further, in this case, the transfer characteristic fixedly set in the nonlinear portion correction filter 41 is a transfer characteristic that corrects distortion due to the nonlinear characteristic of the speaker 2 under a standard environment.

The embodiments of the present invention have been described above.
As described above, according to the present embodiment, the distortion due to the nonlinear characteristics of the speaker 2 is handled by the nonlinear part correction filter 41. Therefore, the adaptive filter composed of the linear inverse filter 42 and the adaptive algorithm execution part 43 is used as the speaker. 2. As a result, the distortion of the output of the speaker 2, including the distortion due to the nonlinear characteristic of the speaker 2, can be corrected with a relatively simple configuration. can be done.

Here, in the above embodiment, the speaker 2, the sensor 3, and the correction device 4 may be integrated as a speaker unit.

REFERENCE SIGNS LIST 1 correction characteristic control unit 2 speaker 3 sensor 4 correction device 5 audio device 41 non-linear correction filter 42 linear inverse filter 43 adaptive algorithm execution unit 44 error calculation unit .

Claims (6)

A speaker distortion correction device for correcting distortion of speaker output with respect to an input signal,
a sensor that detects vibration of the vibration system of the speaker;
a nonlinear correction filter that receives the input signal;
a linear inverse filter that receives the output of the nonlinear portion correction filter as an input and outputs an output signal that drives the speaker;
an adaptive algorithm execution unit that executes a predetermined adaptive algorithm and updates the transfer characteristic of the linear inverse filter so that the vibration detected by the sensor is a vibration without distortion with respect to the input signal;
1. A speaker distortion correcting apparatus, wherein a transfer characteristic for correcting distortion of an output of said speaker with respect to said input signal due to a nonlinear characteristic of said speaker is set in said nonlinear portion correcting filter. A speaker distortion correction device for correcting distortion of speaker output with respect to an input signal,
a nonlinear correction filter that receives the input signal;
a linear inverse filter that receives the output of the nonlinear portion correction filter as an input and outputs an output signal that drives the speaker;
The nonlinear part correction filter has a transfer characteristic that corrects distortion of the output of the speaker with respect to the input signal due to the nonlinear characteristic of the speaker,
A speaker distortion correcting apparatus, wherein the linear inverse filter is set with a transfer characteristic for correcting distortion of an output of the speaker with respect to the input signal due to a linear characteristic of the speaker. The speaker distortion correcting device according to claim 1 or 2,
environment detection means for detecting at least one of the ambient temperature and the aging time of the speaker as an environment;
A loudspeaker distortion correcting apparatus comprising switching control means for switching a transfer characteristic of the non-linear part correction filter to a transfer characteristic suitable for the non-linear characteristic of the speaker estimated from the environment detected by the environment detecting means. . The speaker distortion correcting device according to claim 1 or 2,
measuring means for measuring nonlinear characteristics of the speaker;
A distortion correcting device for a loudspeaker, comprising switching control means for switching the transfer characteristic of the non-linear part correction filter to a transfer characteristic suitable for the non-linear characteristic of the loudspeaker measured by the measuring means. A speaker distortion correcting device according to claim 3 or 4,
a state detection means for detecting a state of an audio device that reproduces an audio signal and outputs it as the input signal;
The switching control means switches the transfer characteristic of the nonlinear portion correction filter at a predetermined timing,
The predetermined timing includes timing when the audio device is activated, timing when the audio device is not reproducing a significant audio signal, timing when the audio device changes the output level of the input signal, and reproduction. A distortion correcting device for a loudspeaker, comprising at least one timing of switching a sound source of an audio signal. 6. A speaker unit comprising the speaker distortion correction device according to claim 1, 2, 3, 4, or 5, and the speaker in a form in which the distortion correction device and the speaker are integrated. .

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