Speaker over-amplification suppression device

Abstract

To provide a "speaker over-amplification suppression device" that more precisely controls the amplitude of the speaker's vibration system to a targeted amplitude range.SOLUTION: An amplitude control unit 6 adjusts the gain of a sound source output signal output by a sound source device 5 and outputs it to an amplifier 4 that drives a speaker 2. The amplitude control unit 6 corrects the displacement of the speaker 2 predicted from the sound source output signal on the basis of the equivalent circuit of the speaker 2 by using an actual value during a past period of the difference between the predicted displacement of the speaker 2 and the displacement of the vibration system of the speaker 2 detected by the displacement detection unit 7 using the sensor 3, and adjusts the gain of the sound source output signal such that the corrected displacement does not exceed a target displacement width.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a technique for suppressing excessive amplitude of a vibration system of a speaker. [Background technology]

[0002] Since a speaker vibrates by passively displacing its vibration system according to the magnitude of the input signal, if the input signal becomes excessive, excessive amplitude will occur, causing abnormalities in the speaker, such as the bottoming out of the speaker's voice coil bobbin or the displacement of the elastic body reaching the breaking range and damaging the vibration system components.

[0003] As a technique for suppressing the occurrence of such excessive amplitude in the vibration system of a speaker, a technique is known in which a predicted value of the displacement of the vibration system of the speaker in response to an input signal is calculated based on an equivalent circuit of the speaker, and if the predicted value is greater than a predetermined threshold value, amplitude control is performed on the input signal (for example, Patent Documents 1 and 2).

[0004] Additionally, known technologies related to the present application include a technology for detecting the actual displacement of a speaker's vibration system using a sensor, and a technology for detecting the input voltage, input current, and displacement of the vibration system of an actual speaker, and updating each characteristic of the speaker's equivalent circuit based on the detected values ​​to characteristics that match the actual speaker (for example, Patent Document 3). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2018 / 116861 [Patent Document 2] JP 2013-55676 A [Patent Document 3] JP 2022-143855 A Summary of the Invention [Problem to be solved by the invention]

[0006] According to the above-mentioned technology of controlling amplitude using a predicted value of the displacement of the vibration system of a speaker based on the equivalent circuit of the speaker, it may not be possible to accurately predict the displacement of the speaker due to factors such as the degree of reproducibility of the equivalent circuit, variations in individual speakers, and changes in the characteristics of each speaker over time.

[0007] For this reason, it is necessary to perform amplitude control with a margin for the target amplitude range, and as a result, the speaker performance cannot be fully utilized. Therefore, an object of the present invention is to control the amplitude of the vibration system of a speaker to a target amplitude range with higher accuracy. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides a speaker over-amplitude suppression device for suppressing over-amplitude of the vibration system of a speaker with respect to an input signal, the device comprising: a displacement detection means for detecting a displacement of the vibration system of the speaker; and an amplitude control section for receiving the input signal. Here, the amplitude control section comprises: a gain adjustment means for adjusting the input signal with a set gain and outputting the signal to the speaker; a displacement prediction means for predicting a displacement of the vibration system of the speaker from the input signal; a predicted displacement correction means for correcting the displacement predicted by the displacement prediction means; and a gain setting means for setting a gain for the gain adjustment means that attenuates the displacement corrected by the predicted displacement correction means to a displacement that does not exceed a predetermined displacement width. The predicted displacement correction means calculates the difference between a displacement predicted by the displacement prediction means in the past and a displacement detected by the displacement detection means corresponding to the input signal that predicted the displacement, and corrects the displacement predicted by the displacement prediction means by an amount corresponding to the calculated difference.

[0009] In order to achieve the above object, the present invention provides a speaker over-amplitude suppression device for suppressing over-amplitude of the vibration system of a speaker with respect to an input signal, the device comprising: a displacement detection means for detecting a displacement of the vibration system of the speaker, a band division means for dividing the input signal into input signals of each band, an amplitude control section provided corresponding to each of the bands and receiving the input signal of the corresponding band divided by the band division means, and a mixer. Here, each of the amplitude control sections comprises a gain adjustment means for adjusting the input signal of the corresponding band with a set gain and outputting the input signal to the mixer, a displacement prediction means for predicting the displacement of the vibration system of the speaker from the input signal of the corresponding band, a predicted displacement correction means for correcting the displacement predicted by the displacement prediction means, and a gain setting means for setting a gain in the gain adjustment means that attenuates the displacement corrected by the predicted displacement correction means to a displacement that does not exceed a predetermined displacement width. The predicted displacement correction means calculates a difference between a displacement predicted by the displacement prediction means in the past and a component of the corresponding band of the displacement detected by the displacement detection means, which corresponds to the input signal of the corresponding band for which the displacement was predicted, and corrects the displacement predicted by the displacement prediction means by an amount according to the calculated difference. Also, the mixer mixes the input signals of each band output from the gain adjustment means of each amplitude control unit, and outputs the result to the speaker.

[0010] In order to achieve the above object, the present invention provides a speaker over-amplitude suppression device for suppressing over-amplitude of a speaker vibration system with respect to an input signal, the device comprising: a displacement detection means for detecting a displacement of the vibration system of the speaker, a band splitting means for splitting the input signal into a low-frequency input signal and a high-frequency input signal, an amplitude control section for receiving the low-frequency input signal split by the band splitting means, and a mixer. Here, the amplitude control section comprises: a gain adjustment means for adjusting the low-frequency input signal with a set gain and outputting the low-frequency input signal to the mixer, a displacement prediction means for predicting the displacement of the vibration system of the speaker from the low-frequency input signal, a predicted displacement correction means for correcting the displacement predicted by the displacement prediction means, and a gain setting means for setting a gain in the gain adjustment means that attenuates the displacement corrected by the predicted displacement correction means to a displacement that does not exceed a predetermined displacement width. The amplitude control unit includes a gain adjusting unit that adjusts the amplitude of the input signal from the gain control unit and a high-frequency component of the input signal from the band dividing unit, and the high-frequency component of the input signal from the gain adjusting unit is mixed with the low-frequency component of the input signal from the band dividing unit and the high-frequency component of the input signal from the band dividing unit.

[0011] Here, the speaker excessive amplitude suppression device may be configured so that the predicted displacement correction means corrects the displacement predicted by the displacement prediction means by the maximum value of the difference calculated up to now. Furthermore, the above speaker over-amplitude suppression device may be configured so that, when the gain setting means attenuates the displacement corrected by the predicted displacement correction means to a displacement that does not exceed a predetermined displacement range, the gain setting means sets in the gain adjustment means a gain that attenuates the displacement to a displacement that does not exceed the displacement range when the gain setting means is smaller than the gain currently set in the gain adjustment means.

[0012] Furthermore, the above speaker over-amplitude suppression device may be provided with an input detection means for detecting an input to the speaker, and a speaker equivalent circuit updating means, the displacement prediction means predicting a displacement of the vibration system of the speaker in accordance with a set equivalent circuit of the speaker, and the speaker equivalent circuit updating means updating characteristics of the equivalent circuit set in the displacement prediction means so as to match the relationship between the speaker input detected by the input detection means and the displacement detected by the displacement detection means in response to the input.

[0013] According to the speaker over-amplitude suppression device described above, an error in the currently predicted displacement is estimated based on the past difference between the displacement predicted by the displacement prediction means from the input signal and the displacement actually detected by the displacement detection means for that input signal, the predicted displacement is corrected by that error amount, and amplitude control is performed based on the corrected displacement, so that the amplitude of the vibration system of the speaker can be controlled to a target amplitude range more accurately than when amplitude control is performed based only on the displacement predicted by the displacement prediction means.

[0014] In order to achieve the above object, the present invention provides a speaker over-amplitude suppression device for suppressing over-amplitude of a speaker vibration system with respect to an input signal, the device comprising: a displacement detection means for detecting a displacement of the vibration system of the speaker, an input detection means for detecting an input to the speaker, and an amplitude control section for receiving the input signal. Here, the amplitude control section comprises: a gain adjustment means for adjusting the input signal with a set gain and outputting the input signal to the speaker, a displacement prediction means for predicting the displacement of the vibration system of the speaker from the input signal according to a set equivalent circuit of the speaker, a gain setting means for setting a gain in the gain adjustment means for attenuating the displacement predicted by the displacement prediction means to a displacement that does not exceed a predetermined displacement width, and a speaker equivalent circuit update means for updating the characteristics of the equivalent circuit set in the displacement prediction means so as to match the relationship between the input detected by the input detection means and the displacement detected by the displacement detection means with respect to the input.

[0015] According to such a speaker over-amplitude suppression device, the characteristics of the equivalent circuit used by the displacement prediction means to predict the displacement of the vibration system can be updated at any time using the actual displacement of the vibration system of the speaker detected by the displacement detection means so as to match the actual speaker characteristics. As a result, the accuracy of the displacement prediction can be improved compared to a case where the characteristics of the equivalent circuit using the actual displacement of the vibration system of the speaker is not updated, and the amplitude of the vibration system of the speaker can be controlled to a target amplitude range with higher accuracy. Effect of the Invention

[0016] As described above, according to the present invention, it is possible to more accurately control the amplitude of the vibration system of a speaker to a target amplitude range. [Brief description of the drawings]

[0017] [Figure 1] 1 is a diagram showing a configuration of an audio system according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing a configuration for displacement detection according to the first embodiment of the present invention. [Diagram 3] 2 is a diagram showing a configuration of an attenuator gain control section according to the first embodiment of the present invention. FIG. [Figure 4] FIG. 2 is a diagram showing an equivalent circuit of a speaker used in the first embodiment of the present invention. [Diagram 5] 5 is a flowchart showing a speaker displacement error calibration process according to the first embodiment of the present invention. [Figure 6] FIG. 4 is a diagram illustrating an example of amplitude control according to the first embodiment of the present invention. [Figure 7] FIG. 11 is a diagram showing a configuration of an attenuator gain control section according to a second embodiment of the present invention. [Figure 8] FIG. 13 is a diagram illustrating a configuration of an attenuator gain control section according to a third embodiment of the present invention. [Figure 9] FIG. 13 is a diagram showing a configuration of an amplitude control section according to a fourth embodiment of the present invention. [Figure 10] FIG. 13 is a diagram showing a configuration of an amplitude control section according to a fifth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] A first embodiment of the present invention will now be described. FIG. 1 shows the configuration of an audio system according to the first embodiment. As shown in the figure, the acoustic system includes a control unit 1, a speaker 2, a sensor 3 provided in the speaker 2, an amplifier 4, a sound source device 5 that outputs a sound source output signal S which is an audio signal, an amplitude control unit 6, and a displacement detection unit 7 that measures the displacement Xs of the vibration system of the speaker 2 from the output of the sensor 3. Then, the amplitude control unit 6 adjusts the gain of the sound source output signal, which is the audio signal output by the sound source device 5, and outputs it to the amplifier 4 as an intermediate output signal. The amplifier 4 amplifies the intermediate output signal with a predetermined gain to generate an amplifier output signal, and drives the speaker 2 with the amplifier output signal. The control unit 1 also receives inputs from the sound source device 5 such information as the playback state (music playing / music not playing), information on the audio content being played, and the output level (volume, etc.). Next, the amplitude control section 6 includes an all-pass filter 61 , an attenuator 62 , and an attenuator gain control section 63 . The all-pass filter 61 outputs an audio signal obtained by delaying the sound source output signal S output by the sound source device 5 by a predetermined delay time to the attenuator 62. This delay time will be described later. The attenuator gain control unit 63 calculates and sets the gain of the attenuator 62 from the displacement Xs of the vibration system of the speaker 2 detected by the displacement detection unit 7 and the sound source output signal S output by the sound source device 5. The attenuator gain control unit 63 will be described in detail later. Then, the attenuator 62 adjusts the level of the audio signal output from the all-pass filter 61 with a gain set by an attenuator gain control section 63, and outputs the adjusted level to the amplifier 4 as an intermediate output signal. Next, FIG. 2a shows the configuration of the speaker 2. As shown in the figure, the speaker 2 has a yoke 201, a magnet 202, a top plate 203, a voice coil bobbin 204, a voice coil 205, a frame 206, a damper 207, a diaphragm 208, an edge 209, a dust cap 210, and a displacement detection magnet 211. With the top of the figure being the front of speaker 2 and the bottom being the rear of speaker 2, yoke 201 has a protruding part 2011 protruding forward in the center, with an annular magnet 202 provided on the outer periphery of protruding part 2011, and an annular top plate 203 provided on magnet 202. Top plate 203 is made of a conductive material such as iron. A magnetic circuit 220 is formed by yoke 201, magnet 202, and top plate 203.

[0019] Voice coil bobbin 204 has a hollow cylindrical shape, and voice coil 205 to which a signal from amplifier 4 is applied is wound around the outer periphery. Furthermore, convex portion 2011 of yoke 201 is inserted into the hollow of voice coil bobbin 204 from the rear so that voice coil bobbin 204 can move back and forth with respect to yoke 201, and voice coil 205 is disposed at a position between convex portion 2011 of yoke 201 and top plate 203, where magnetic flux generated between the inner circumferential ends of top plate 203 by magnetic circuit 220 passes.

[0020] Diaphragm 208 has a shape similar to the side surface of a truncated cone whose height direction is the front-to-rear direction of speaker 2, and its outer circumferential end is connected to the front end of frame 206 by edge 209. In addition, the inner circumferential end of diaphragm 208 is fixed to the front end of voice coil bobbin 204.

[0021] In such a configuration of the speaker 2, when an output signal from the amplifier 4 is applied to the voice coil 205, the voice coil bobbin 204 vibrates back and forth according to the amplitude of the output signal due to the electromagnetic interaction between the magnetic flux generated by the magnetic circuit 220 and the signal flowing through the voice coil 205. When the voice coil bobbin 204 vibrates, the diaphragm 208 connected to the voice coil bobbin 204 vibrates, and a sound according to the signal from the amplifier 4 is generated.

[0022] The displacement detection magnet 211 is fixed to the outer periphery of the voice coil bobbin 204 so as to move up and down together with the voice coil bobbin 204 , and generates a magnetic flux perpendicular to the magnetic flux generated by the magnetic circuit 220 . Here, the above-mentioned sensor 3 is fixed to a position close to the displacement detection magnet in a non-vibration system of the speaker 2, such as the top plate 203. The sensor 3 is a magnetic angle sensor, and detects and outputs the arctangent Qs / Qc of the angle of a resultant vector Q of a magnetic flux vector Qc acting from the magnetic circuit 220 and a magnetic flux vector Qs acting from the displacement detection magnet 211 as a magnetic angle, as shown in Fig. 2b. The magnetic flux vector generated by the displacement detection magnet acting on the sensor 3 changes due to the displacement of the displacement detection magnet 211 accompanying the displacement of the voice coil bobbin 204, so this magnetic angle has a value according to the amount of displacement of the voice coil bobbin 204.

[0023] As shown in FIG. 1, the displacement detection unit 7 measures the displacement of the vibration system of the speaker 2 from the output of the sensor 3, and outputs it to the attenuator gain control unit 63 as a displacement Xs. Next, FIG. 3 shows the configuration of the attenuator gain control section 63 of the amplitude control section 6. As shown in FIG. As shown in the figure, the attenuator gain control section 63 includes a speaker displacement prediction section 631 , a delay unit 632 , a speaker displacement error calibration section 633 , an attenuator gain calculation section 634 , and an attenuator gain initial value setting section 635 . The speaker displacement prediction unit 631 predicts the displacement of the vibration system of the speaker 2 due to the sound source output signal S(n) output by the sound source device 5 according to a preset equivalent circuit (speaker model) of the speaker 2, and outputs it as a predicted displacement Xp(n). Here, as the equivalent circuit of the speaker 2, for example, the equivalent circuit shown in FIG. 4 can be used. Moreover, when the equivalent circuit shown in FIG. 4 is used, the predicted displacement Xp(n) can be obtained by the following formula (1). Formula (1); Xp(n)=-a1Xp(n-1)-a2Xp(n-2)-a3Xp(n-3)+{b0S(n)+b1S(n-1)+b2S(n-2)+b3S(n-3)}A a0=R e K ms +2F s (R e R ms +L e K ms +Bl 2 )+4F s 2 (R e M ms +L e R ms )+8F s 3 (M ms L e ) a1={3R e K ms +2F s (R e R ms +L e K ms +Bl 2 4F s 2 (R e M ms +L e R ms )24F s 3 (M ms L e )} / a0 a2={3R e K ms 2F s (R e R ms +L e Kms +Bl 2 4F s 2 (R e M ms +L e R ms )+24F s 3 (M ms L e )} / a0 a3={R e K ms 2F s (R e R ms +L e K ms +Bl 2 )+4F s 2 (R e M ms +L e R ms )8F s 3 (M ms L e )} / a0 b0=Bl / a0 b1=3Bl / a0 b2=3Bl / a0 b3=Bl / a0 where A is the gain of the amplifier 4, Xp is time series data, and Xp(i) is the i-th data of the predicted displacement Xp. Also, S is time series data, and S(i) is the i-th data of the sound source output signal S. Also, F s is the sampling frequency of these time series data.

[0024] Here, if the value of the gain A of the amplifier 4 is known from a set value, a design value, or the like, then that value is used. Furthermore, if the value of the gain A of the amplifier 4 is not known, the gain A can be calculated, for example, as follows. That is, immediately after starting up the acoustic system, a test signal having a frequency close to the inaudible range (e.g., 20 Hz) within the range in which the sensor 3 can detect the displacement is output from the sound source device 5 as the sound source output signal S(n), and the gain A can be obtained by solving the following equation (2) using the displacement Xs detected by the displacement detection unit 7.

[0025] Formula (2); Xs(n)=-a1Xs(n-1)-a2Xs(n-2)-a3Xs(n-3)+{b0S(n)+b1S(n-1)+b2S(n-2)+b3S(n-3)}A It should be noted that Xs is time series data, and Xs(i) represents the i-th data of the displacement Xs.

[0026] Here, the speaker displacement prediction unit 631 may calculate the predicted displacement Xp(n) using an equivalent circuit different from that shown in FIG. Alternatively, the correspondence between the sound source output signal S and the displacement Xp may be set in advance in the speaker displacement prediction unit 631, and the predicted displacement Xp(n) may be calculated in accordance with the correspondence set in the speaker displacement prediction unit 631. Returning to FIG. 3, the predicted displacement Xp(n) calculated by the speaker displacement prediction unit 631 is output to the speaker displacement error calibration unit 633 and the delay unit 632. The delay unit 632 delays the input predicted displacement Xp(n) by Td and outputs it as a delayed predicted displacement Xp(n-Td) to the speaker displacement error calibration unit 633. Here, Td corresponds to the delay until the displacement Xs corresponding to the predicted displacement Xp(n) is detected by the displacement detection unit 7. The speaker displacement error calibration unit 633 performs speaker displacement error calibration processing using the predicted displacement Xp(n) input from the speaker displacement prediction unit 631, the delayed predicted displacement Xp(n-Td) input from the delay unit 632, and the displacement Xs(n) input from the displacement detection unit 7, corrects the error in the predicted displacement Xp(n), and outputs the corrected predicted displacement X(n) to the attenuator gain calculation unit 634.

[0027] 5 shows the procedure of the speaker displacement error calibration process performed by the speaker displacement error calibration unit 633. Here, the speaker displacement error calibration process is repeatedly executed continuously or intermittently. As shown in the figure, in this process, first, a prediction error ΔX(n) is calculated by Xs(n)-Xp(n-Td) (step 502). Then, it is checked whether the predicted error ΔX(n) is 0 (step 504). If it is 0, the measured displacement Xp(n) is output as the calibrated predicted displacement X(n) to the attenuator gain calculation unit 634 (step 506), and the current speaker displacement error calibration process is terminated. On the other hand, if it is determined in step 504 that the predicted error ΔX(n) is not 0, it is checked whether the predicted error ΔX(n) is greater than 0 (step 508), and if it is greater, it is further checked whether Xp(n) is less than 0 (step 510). If it is less than 0, the measured displacement Xp(n) is output as it is to the attenuator gain calculation unit 634 as the calibrated predicted displacement X(n) (step 506), and the current speaker displacement error calibration process is terminated.

[0028] On the other hand, if it is determined in step 510 that Xp(n) is not smaller than 0, then absMAX(a, b) is a function that outputs a when the absolute value of a is equal to or greater than the absolute value of b, and outputs b otherwise, and ΔmaxX(n) is calculated by ΔmaxX(n) = absMAX{ΔX(n), ΔPXR} (step 512). Therefore, if the absolute value of ΔX(n) is equal to or greater than the absolute value of ΔPXR, then ΔmaxX(n) = ΔX(n), and if the absolute value of ΔX(n) is smaller than the absolute value of ΔPXR, then ΔmaxX(n) = ΔPXR.

[0029] The initial value of ΔPXR is 0. Then, ΔPXR is updated to ΔmaxX(n) (step 514). Moreover, the calibrated predicted displacement X(n) is calculated by X(n)=Xp(n)+ΔPXR and output to the attenuator gain calculation unit 634 (step 516), and the current speaker displacement error calibration process is terminated. On the other hand, if it is determined in step 508 that the predicted error ΔX(n) is not greater than 0, that is, if the predicted error ΔX(n) is less than 0, then it is checked whether Xp(n) is greater than 0 (step 518). If it is greater than 0, the measured displacement Xp(n) is output as the calibrated predicted displacement X(n) to the attenuator gain calculation unit 634 (step 506), and the current speaker displacement error calibration process is terminated.

[0030] On the other hand, if it is determined in step 518 that Xp(n) is not greater than 0, ΔmaxX(n) is calculated by ΔmaxX(n)=absMAX{ΔX(n), ΔNXR} (step 520). The initial value of ΔNXR is set to 0. Then, ΔNXR is updated to ΔmaxX(n) (step 522). Moreover, the calibrated predicted displacement X(n) is calculated by X(n)=Xp(n)+ΔNXR and output to the attenuator gain calculation unit 634 (step 524), and the current speaker displacement error calibration process is terminated. The speaker displacement error calibration process performed by the speaker displacement error calibration unit 633 has been described above. Here, ΔPXR and ΔNXR set in steps 514 and 522 of the above speaker displacement error calibration process indicate values ​​that represent the maximum absolute values ​​of the positive and negative errors of the predicted displacement Xp with respect to the displacement Xs during the period up to now. Therefore, the calibrated predicted displacement X(n) calculated in steps 516 and 524 is the predicted displacement Xp(n) corrected by the maximum past error. In addition, when the prediction error ΔX(n) is greater than 0 and Xp(n) is less than 0 (steps 508, 510), or when the prediction error ΔX(n) is less than 0 and Xp(n) is greater than 0 (steps 508, 518), ΔPXR / ΔNXR is not updated and the predicted displacement Xp(n) is not corrected using ΔPXR / ΔNXR. This is because, in this case, even if correction using ΔPXR / ΔNXR is performed, the absolute value of the calibrated predicted displacement X(n) will be smaller than the absolute value of the predicted displacement X(n) and the predicted error ΔX(n), and therefore it is not appropriate to take the prediction error ΔX(n) into consideration when correcting the predicted displacement X(n) to suppress excessive amplitude.

[0031] Note that, in the above speaker displacement error calibration process, if it is determined in step 504 that the predicted error ΔX(n) is 0, instead of step 506, a process may be performed in which one of X(n) = Xp(n) + ΔPXR and X(n) = Xp(n) + ΔNXR, whichever has the larger absolute value, is calculated as the calibrated predicted displacement X(n) and output to the attenuator gain calculation unit 634.

[0032] Returning to FIG. 3, the attenuator gain initial value setting section 635, under the control of the control section 1, sets an initial value of the attenuator gain in the attenuator gain calculation section 634 (for example, 0 dB). Here, the control unit 1 causes the attenuator gain initial value setting unit 635 to set an initial value of the attenuator gain when the audio system is initialized, when the audio system is started up, when the output level (volume) of the sound source device 5 is reduced, when the content being played back by the sound source device 5 is changed, etc. Next, the attenuator gain calculation unit 634 calculates the attenuator gain G, and if the attenuator gain G has changed, sets the attenuator gain G after the change in the attenuator 62 as the gain of the attenuator 62 . As described above, the attenuator 62 adjusts the level of the audio signal output from the all-pass filter 61 with the gain set by the attenuator gain control, and outputs the adjusted level to the amplifier 4 as an intermediate output signal. The attenuator gain calculation unit 634 calculates the attenuator gain G as follows. That is, a target displacement TrgX is preset in the attenuator gain calculation unit 634. The target displacement TrgX is the maximum absolute value of the displacement permitted for the vibration system of the speaker 2. For example, when a displacement between +1.0 mm and -1.0 mm is permitted for the vibration system of the speaker 2, 1.0 mm is set as the target displacement TrgX.

[0033] Furthermore, when an initial value of the attenuator gain is set by the attenuator gain initial value setting section 635, the attenuator gain calculation section 634 sets the attenuator gain G to the set initial value. Thereafter, the calibrated predicted displacement X(n) output from the speaker displacement error calibration unit 633 is compared with the target displacement TrgX, and if the absolute value of the calibrated predicted displacement X(n) is greater than the target displacement TrgX, TrgX / |X(n)|, which is the ratio of the target displacement TrgX to the absolute value of the calibrated predicted displacement X(n), is calculated. Then, if the gain represented by TrgX / |X(n)| is smaller than the current attenuator gain G (if the gain is such that the amount of attenuation increases), the attenuator gain G is updated to the gain represented by TrgX / |X(n)|. In calibrating the attenuator gain control unit 63, the delay time of the all-pass filter 61 in FIG. 1 described above is a delay time from when the predicted displacement Xp(n) is output from the speaker displacement prediction unit 631 to when the attenuator gain calculation unit 634 updates the attenuator gain G in response to the calibrated predicted displacement X(n) output from the speaker displacement error calibration unit 633 and sets it in the attenuator 62. The delay time is dominated by the time required for the speaker displacement prediction unit 631 to calculate the predicted displacement Xp(n).

[0034] FIG. 6 shows an example of a simulation effect of amplitude control using the amplitude control section 6 as described above. The illustrated example is when the target displacement TrgX is set to 1.0 mm. When the sound source output signal S output by the sound source device 5 is output directly to the amplifier 4 without amplitude control, the vibration system of the speaker 2 vibrates between +2.5 mm and -2.5 m as shown by line A. When the amplitude control of the first embodiment is performed on the same sound source output signal S, the vibration of the vibration system of the speaker 2 can be made to have a displacement range between +1.0 mm and -1.0 m as shown by line B.

[0035] The delay in vibration when amplitude control is performed (line B) compared to when amplitude control is not performed (line A) is due to the delay of the all-pass filter 61. The first embodiment of the present invention has been described above. Here, the speaker displacement error calibration process in the first embodiment may be performed continuously or intermittently over the entire period during which the audio system is in operation, or may be performed repeatedly only during a specified period such as when the audio system is initialized, when the audio system is started up, when the output level (volume) of the sound source device 5 changes, or between playback of content of the sound source device 5 (for example, between songs if the content is a musical piece).

[0036] However, when the speaker displacement error calibration process is performed only during a predetermined period, after the period has elapsed, the speaker displacement error calibration unit 633 performs error-fixed speaker displacement error calibration process. Here, the error-fixed speaker displacement error calibration process skips steps 512, 514, 520, and 522 of the speaker displacement error calibration process in Fig. 5, and fixes ΔPXR and ΔNXR used in steps 516 and 524 to ΔPXR and ΔNXR finally found by the speaker displacement error calibration process performed during the predetermined period.

[0037] As described above, according to the first embodiment, an error in the currently predicted displacement is estimated based on the difference between the displacement previously predicted by the speaker displacement prediction unit 631 from the sound source output signal S and the displacement actually detected by the displacement detection unit 7 for the sound source output signal S, the predicted displacement is corrected by the error amount, and amplitude control is performed based on the corrected displacement. Therefore, it is possible to control the amplitude of the vibration system of the speaker 2 to be within the target amplitude range more accurately than when amplitude control is performed based only on the displacement predicted by the speaker displacement prediction unit 631.

[0038] A second embodiment of the present invention will now be described. The second embodiment differs from the first embodiment in that a speaker input sensor 701 is provided to detect the current flowing through the speaker 2 and the input voltage of the speaker 2, as shown in FIG. 7, and in that the attenuator gain control unit 63 has the configuration shown in FIG. 7. As shown in FIG. 7, the attenuator gain control unit 63 of the second embodiment is obtained by providing the attenuator gain control unit 63 of the first embodiment shown in FIG. 3 with a speaker model update unit 636 that updates the characteristics of the equivalent circuit used by the speaker displacement prediction unit 631 to predict the displacement of the vibration system.

[0039] The control unit 1 controls the open-pass filter and attenuator 62 of the amplitude control unit 6 to output the input signal as is without modification when the sound system is initialized, when the sound system is started up, when the output level (volume) of the sound source device 5 changes, between playback of content from the sound source device 5 (for example, between songs if the content is music), etc., and causes the sound source device 5 to output an appropriate output signal such as a test signal, music signal, or acoustic watermark signal as a sound source output signal, and also causes the speaker model update unit 636 to perform an update operation of the equivalent circuit.

[0040] In the updating operation, the speaker model updating unit 636 finds the characteristics of an equivalent circuit that matches the behavior of the speaker 2 from measurement values ​​such as the current flowing through the speaker 2 detected by the speaker input sensor 701, the input voltage of the speaker 2, and the displacement Xs detected by the displacement detection unit 7, and updates the characteristics of the equivalent circuit that the speaker displacement prediction unit 631 uses to predict the displacement of the vibration system to the found characteristics.

[0041] For example, if the desired characteristic of the equivalent circuit is the K ms (x); Stiffness (rigidity), the speaker model update unit 636 can perform calculation based on the measurement value as follows. That is, the resonance frequency fs of the impedance Z=u / i of the speaker 2 is detected from the current i flowing through the speaker 2 and the input voltage u of the speaker 2. ms ; Using mechanical mass, K ms (x)=(2πfs) 2 M ms Calculate the displacement Xs of the vibration system of speaker 2 output by sensor 3 and K ms (Xs) and calculate the nonlinear K ms Calculate the properties of (Xs).

[0042] Here, K ms The calculation of the nonlinear characteristics of (Xs) is done in advance by ms Prepare multiple patterns of nonlinear characteristics of (Xs), and calculate the displacement x and K ms A pattern that matches the relationship with (Xs) is K ms This may be done by calculating the nonlinear characteristics of (Xs).

[0043] According to such an acoustic system, the characteristics of the equivalent circuit used by the speaker displacement prediction unit 631 to predict the displacement of the vibration system can be updated at any time using the actual displacement of the vibration system of the speaker 2 detected by the displacement detection unit 7 so as to closely match the actual characteristics of the speaker 2. A third embodiment of the present invention will now be described. The third embodiment differs from the second embodiment only in the configuration of the attenuator gain control section 63. FIG. 8 shows a configuration of an attenuator gain control section 63 according to the third embodiment. As shown in the figure, the attenuator gain control unit 63 of the third embodiment does not include the delay unit 632 and the speaker displacement error calibration unit 633 of the attenuator gain control unit 63 of the second embodiment shown in FIG. 7, and outputs the predicted displacement Xp(n) calculated by the speaker displacement prediction unit 631 to an attenuator gain calculation unit 634.

[0044] In the third embodiment, the attenuator gain calculation unit 634 calculates the attenuator gain G shown in the first embodiment by using the predicted displacement Xp(n) instead of the calibrated predicted displacement X(n). According to such an acoustic system, the characteristics of the equivalent circuit used by the speaker displacement prediction unit 631 to predict the displacement of the vibration system can be updated at any time using the actual displacement of the vibration system of the speaker 2 detected by the displacement detection unit 7 so as to match the actual characteristics of the speaker 2. As a result, the accuracy of the prediction of the displacement is improved compared to the case where the characteristics of the equivalent circuit are not updated using the actual displacement of the vibration system of the speaker 2, and the amplitude of the vibration system of the speaker 2 can be controlled to the target amplitude range with higher accuracy.

[0045] The fourth embodiment of the present invention will now be described. The fourth embodiment of the present invention differs from the first embodiment in the configuration of the amplitude control section 6. FIG. 9 shows the configuration of the amplitude control section 6 of the fourth embodiment. As shown in the figure, the amplitude control section 6 of the fourth embodiment includes a sound source output signal band dividing section 901, a displacement signal band dividing section 902, a plurality of band-specific amplitude control sections 903, and a mixer 904. All of the band amplitude control sections 903 have the same configuration as any one of the amplitude control sections 6 in the first, second, or third embodiment, and perform the same processing. Each band amplitude control unit 903 is provided corresponding to each of the multiple bands obtained by dividing the entire band of the sound source output signal S. The sound source output signal band dividing unit 901 divides the sound source output signal S output by the sound source device 5 into bands and outputs the sound source output signal S of each band to the band amplitude control unit 903 corresponding to that band. The displacement signal band dividing unit 902 divides the displacement signal Xs output by the displacement detection unit 7 into bands and outputs the displacement signal Xs of each band to the band amplitude control unit 903 corresponding to that band.

[0046] The signals output by each band amplitude control section 903 after performing the above-mentioned processing on the sound source output signal S and the displacement signal Xs of the corresponding band are input to a mixer 904 . Mixer 904 mixes the signals input from each band amplitude control section 903 and outputs the mixed signal to amplifier 4 as an intermediate output signal. By using the amplitude control section 6 as shown in FIG. 9 to perform amplitude control for each band, it is possible to suppress excessive vibration while suppressing a drop in the overall speaker output level. The fifth embodiment of the present invention will now be described. The fifth embodiment of the present invention differs from the first embodiment in the configuration of the amplitude control section 6. FIG. 10 shows the configuration of the amplitude control section 6 of the fifth embodiment. As shown in the figure, the amplitude control section 6 of the fifth embodiment includes a sound source output signal high frequency / low frequency division section 1001 , a displacement signal low frequency extraction section 1002 , a delay section 1003 , a low frequency amplitude control section 1004 , and a mixer 1005 . The sound source output signal high / low frequency division unit 1001 divides the sound source output signal S output by the sound source device 5 into high frequency components and low frequency components, outputs the high frequency components to the delay unit 1003 and outputs the low frequency components to the low frequency amplitude control unit 1004. The displacement signal low frequency extraction unit 1002 extracts the low frequency components of the displacement signal Xs output by the displacement detection unit 7 , and outputs them to the low frequency amplitude control unit 1004 . The low-frequency amplitude control section 1004 has the same configuration as the amplitude control section 6 in any one of the first, second and third embodiments, and performs the same processing. Then, the low-frequency amplitude control section 1004 performs the above-mentioned processing on the low-frequency sound source output signal S and the displacement signal Xs, and the resulting signals are output to the mixer 904. The delay section 1003 delays the high-frequency component signal of the input sound source output signal S by the amount of delay caused by the processing in the low-frequency amplitude control section 1004 , and outputs the delayed signal to the mixer 904 . Mixer 904 mixes the signals input from delay section 1003 and low-frequency amplitude control section 1004 , and outputs the result to amplifier 4 as an intermediate output signal. Since the large displacement of the vibration system of the speaker 2 is mostly due to low-frequency components, by using an amplitude control section 6 as shown in FIG. 10 to perform amplitude control only on the low-frequency side, it is possible to effectively suppress the vibration while minimizing the overall decrease in the speaker output level.

[0047] As a configuration for performing amplitude control only on the low-frequency side, a configuration in which a plurality of band-by-band amplitude control sections 903 corresponding to a plurality of bands on the low-frequency side of the amplitude control device shown in FIG. 9 are left, and the band-by-band amplitude control section 903 corresponding to the band on the high-frequency side is replaced with a delay section 1003 can also be used.

[0048] The embodiment of the present invention has been described above. [Explanation of symbols]

[0049] 1...control section, 2...speaker, 3...sensor, 4...amplifier, 5...sound source device, 6...amplitude control section, 7...displacement detection section, 61...all-pass filter, 62...attenuator, 63...attenuator gain control section, 201...yoke, 202...magnet, 203...top plate, 204...voice coil bobbin, 205...voice coil, 206...frame, 207...damper, 208...diaphragm, 209...edge, 210...dust cap, 211...magnet for displacement detection, 220...magnetic circuit, 631...speaker Displacement prediction unit, 632... delay unit, 633... speaker displacement error calibration unit, 634... attenuator gain calculation unit, 635... attenuator gain initial value setting unit, 636... speaker model update unit, 701... speaker input sensor, 901... sound source output signal band division unit, 902... displacement signal band division unit, 903... band amplitude control unit, 904... mixer, 1001... sound source output signal high / low frequency division unit, 1002... displacement signal low frequency extraction unit, 1003... delay unit, 1004... low frequency amplitude control unit, 1005... mixer.

Claims

1. A speaker over-amplitude suppression device that suppresses over-amplitude of a vibration system of a speaker with respect to an input signal, comprising: A displacement detection means for detecting a displacement of a vibration system of the speaker; an amplitude control unit that receives the input signal; The amplitude control unit is a gain adjustment means for adjusting the input signal with a set gain and outputting the adjusted signal toward the speaker; a displacement prediction means for predicting a displacement of a vibration system of a speaker from the input signal; a predicted displacement correcting means for correcting the displacement predicted by the displacement predicting means; a gain setting means for setting a gain for attenuating the displacement corrected by the predicted displacement correction means to a displacement that does not exceed a predetermined displacement width in the gain adjustment means; The predicted displacement correction means calculates a difference between a displacement predicted by the displacement prediction means in the past and a displacement detected by the displacement detection means corresponding to the input signal that predicted the displacement, and corrects the displacement predicted by the displacement prediction means by an amount corresponding to the calculated difference.

2. A speaker over-amplitude suppression device that suppresses over-amplitude of a vibration system of a speaker with respect to an input signal, comprising: a displacement detection means for detecting a displacement of a vibration system of the speaker; a band splitting means for splitting the input signal into input signals of respective bands; an amplitude control section provided corresponding to each of the bands, the amplitude control section receiving an input of an input signal of the corresponding band divided by the band dividing means; A mixer. Each of the amplitude control units is a gain adjustment means for adjusting an input signal of a corresponding band with a set gain and outputting the adjusted signal to the mixer; a displacement prediction means for predicting a displacement of a vibration system of a speaker from an input signal of the corresponding band; a predicted displacement correcting means for correcting the displacement predicted by the displacement predicting means; a gain setting means for setting a gain for attenuating the displacement corrected by the predicted displacement correction means to a displacement that does not exceed a predetermined displacement width in the gain adjustment means; the predicted displacement correction means calculates a difference between a displacement predicted by the displacement prediction means in the past and a component of a corresponding band of a displacement detected by the displacement detection means, which corresponds to an input signal of the corresponding band in which the displacement was predicted, and corrects the displacement predicted by the displacement prediction means by an amount according to the calculated difference; The speaker over-amplitude suppression device is characterized in that the mixer mixes input signals of each band output from the gain adjustment means of each amplitude control section and outputs the mixed signal to the speaker.

3. A speaker over-amplitude suppression device that suppresses over-amplitude of a vibration system of a speaker with respect to an input signal, comprising: a displacement detection means for detecting a displacement of a vibration system of the speaker; a band splitting means for splitting the input signal into a low-frequency input signal and a high-frequency input signal; an amplitude control unit receiving the low-frequency input signal divided by the band dividing means; A mixer. The amplitude control unit is a gain adjustment means for adjusting the low-frequency input signal with a set gain and outputting the adjusted low-frequency input signal to the mixer; a displacement prediction means for predicting a displacement of a vibration system of a speaker from the low-frequency input signal; a predicted displacement correcting means for correcting the displacement predicted by the displacement predicting means; a gain setting means for setting a gain for attenuating the displacement corrected by the predicted displacement correction means to a displacement that does not exceed a predetermined displacement width in the gain adjustment means; the predicted displacement correction means calculates a difference between a displacement predicted by the displacement prediction means in the past and the low-frequency component of the displacement detected by the displacement detection means corresponding to the low-frequency input signal for predicting the displacement, and corrects the displacement predicted by the displacement prediction means by an amount corresponding to the calculated difference; The mixer mixes the low-frequency input signal output from the gain adjustment means of the amplitude control unit with the high-frequency input signal divided by the band division means, and outputs the result toward the speaker.

4. 4. The speaker over-amplitude suppression device according to claim 1, 2 or 3, The predicted displacement correction means corrects the displacement predicted by the displacement prediction means by the maximum value of the difference calculated up to now.

5. 4. The speaker over-amplitude suppression device according to claim 1, 2 or 3, The speaker over-amplitude suppression device is characterized in that, when a gain for attenuating the displacement corrected by the predicted displacement correction means to a displacement that does not exceed a predetermined displacement range is smaller than the gain currently set in the gain adjustment means, the gain setting means sets a gain for attenuating the displacement to a displacement that does not exceed the displacement range in the gain adjustment means.

6. 4. The speaker over-amplitude suppression device according to claim 1, 2 or 3, an input detection means for detecting an input to the speaker; A speaker equivalent circuit updating means, the displacement prediction means predicts a displacement of a vibration system of the speaker according to a set equivalent circuit of the speaker; The speaker over-amplitude suppression device is characterized in that the speaker equivalent circuit update means updates the characteristics of the equivalent circuit set in the displacement prediction means so as to match the relationship between the input of the speaker detected by the input detection means and the displacement detected by the displacement detection means with respect to the input.

7. A speaker over-amplitude suppression device that suppresses over-amplitude of a vibration system of a speaker with respect to an input signal, comprising: a displacement detection means for detecting a displacement of a vibration system of the speaker; an input detection means for detecting an input to the speaker; an amplitude control unit that receives the input signal; The amplitude control unit is a gain adjustment means for adjusting the input signal with a set gain and outputting the adjusted signal toward the speaker; a displacement prediction means for predicting a displacement of a vibration system of the speaker from the input signal in accordance with a set equivalent circuit of the speaker; a gain setting means for setting a gain in the gain adjustment means for attenuating the displacement predicted by the displacement prediction means to a displacement that does not exceed a predetermined displacement width; and a speaker equivalent circuit updating means for updating the characteristics of the equivalent circuit set in the displacement prediction means so as to match the relationship between the speaker input detected by the input detection means and the displacement detected by the displacement detection means with respect to the input.

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