Active noise reduction device

Abstract

The noise reduction effect is enhanced by performing noise reduction control that tracks not only changes in the user's position but also changes in the transfer function of the secondary path. [Solution] An active noise reduction device 1 includes a speaker 21 that outputs a canceling sound to cancel out noise, an error microphone 22 that generates an error signal based on the noise and the canceling sound, and a control device 23 that controls the speaker 21 based on the error signal. The control device 23 includes a correction filter ΔC^ that indicates a difference between acoustic characteristics at the position of the error microphone 22 and acoustic characteristics at the position of a user, generates a correction signal by the correction filter ΔC^, corrects the error signal by the correction signal to generate a corrected error signal, adaptively updates a control filter W based on the corrected error signal, generates a canceling estimation signal by a secondary path filter C^, and adaptively updates the secondary path filter C^ based on the canceling estimation signal and the corrected error signal.

Description

[Technical field]

[0001] The present invention relates to an active noise reduction device that reduces noise by interfering with the noise with a canceling sound that is in the opposite phase to the noise. [Background technology]

[0002] In recent years, efforts to provide vulnerable transport users, such as the elderly and children, with access to sustainable transport systems have been gaining momentum. To achieve this, research and development into vehicle comfort has been attracting attention to further improve transport safety and convenience.

[0003] In order to improve the comfort of a vehicle, it is preferable to reduce noise in the vehicle interior. Therefore, active noise reduction devices that reduce noise by interfering with the noise with a canceling sound that is in the opposite phase to the noise have been actively researched and developed.

[0004] For example, Patent Document 1 discloses an active noise control system equipped with a position detection device that detects the position of a user's head. This active noise control system selects one of a plurality of auxiliary filters according to the position of the user's head detected by the position detection device, corrects a microphone error signal (a signal picked up by a microphone) using the output of the selected auxiliary filter, updates a variable filter based on the corrected microphone error signal, and controls a speaker with the updated variable filter. In this way, by selecting one of a plurality of auxiliary filters according to the position of the user's head, it becomes possible to perform noise reduction control that follows changes in the position of the user's head. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 7262899 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the active noise control system in Patent Document 1 does not learn the transfer function of the secondary path from the speaker to the microphone. Therefore, when the transfer function of the secondary path changes due to opening and closing of a window, etc., it is not possible to perform noise reduction control that follows the change in the transfer function of the secondary path, and there is a risk that the noise reduction effect will decrease.

[0007] In view of the above background, an object of the present invention is to provide an active noise reduction device that can enhance the noise reduction effect by performing noise reduction control that follows not only changes in the user's position but also changes in the transfer function of the secondary path, and thereby to contribute to the development of a sustainable transportation system. [Means for solving the problem]

[0008] In order to solve the above problem, one aspect of the present invention is an active noise reduction device (1, 81) including a speaker (21) that outputs a canceling sound to cancel noise, an error microphone (22) that generates an error signal (e) based on the noise and the canceling sound, and a control device (23, 83) that controls the speaker based on the error signal, the control device including a control filter (W) that generates a control signal (u) for controlling the speaker, a secondary path filter (C^) that indicates an estimated value of a transfer function of a secondary path from the speaker to the error microphone, and a correction filter (ΔP^, ΔC^) that indicates a difference between acoustic characteristics at the position of the error microphone and acoustic characteristics at the position of a user, and generates correction signals (x, x1, x2) by the correction filter, and corrects the error signal by the correction signal to generate a corrected error signal (e ear ), adaptively updating the control filter based on the compensation error signal, generating a cancellation estimation signal (ŷ) based on the control signal by the secondary path filter, and adaptively updating the secondary path filter based on the cancellation estimation signal and the compensation error signal.

[0009] According to this aspect, the control device generates a correction signal using a correction filter (a filter that indicates the difference between the acoustic characteristics at the position of the error microphone and the acoustic characteristics at the position of the user), generates a corrected error signal by correcting the error signal using the correction signal, and adaptively updates the control filter based on the corrected error signal. This allows noise reduction control to be performed in accordance with changes in the user's position, thereby improving the noise reduction effect at the user's position. In addition, the control device adaptively updates the secondary path filter based on the cancellation estimation signal and the corrected error signal. This allows noise reduction control to be performed in accordance with changes in the transfer function of the secondary path, thereby further improving the noise reduction effect.

[0010] In the above aspect, the control device may further include a primary path filter (P^) indicating an estimate of a transfer function of a primary path from a noise source to the error microphone, and the correction filter may include a first correction filter (ΔP^) corresponding to the primary path filter and a second correction filter (ΔC^) corresponding to the secondary path filter.

[0011] According to this aspect, the error signal is corrected by the correction signals generated by the first correction filter (correction filter corresponding to the primary path filter) and the second correction filter (correction filter corresponding to the secondary path filter). This makes it possible to more accurately track changes in the user's position compared to a case in which the error signal is corrected only by the correction signal generated by the correction filter corresponding to either the primary path filter or the secondary path filter. This makes it possible to further enhance the noise reduction effect at the user's position.

[0012] In order to solve the above problem, one aspect of the present invention is an active noise reduction device (101) including a speaker (21) that outputs a canceling sound to cancel noise, an error microphone (22) that generates an error signal (e) based on the noise and the canceling sound, and a control device (103) that controls the speaker based on the error signal, the control device including a control filter (W) that generates a control signal (u) for controlling the speaker, a secondary path filter (C^) that indicates an estimated value of a transfer function of a secondary path from the speaker to the error microphone, and a correction filter (ΔC^) that indicates a difference between acoustic characteristics at the position of the error microphone and acoustic characteristics at the position of a user, and a correction signal (x2) is generated by the correction filter, and the error signal is corrected by the correction signal to generate a corrected error signal (e ear ), obtain a reference signal (r) corresponding to the noise, and generate a compensated reference signal (r) based on the reference signal by the secondary path filter and the compensation filter. x ), adaptively updating the control filter based on the corrected error signal and the corrected reference signal, generating a cancellation estimation signal (ŷ) based on the control signal by the secondary path filter, and adaptively updating the secondary path filter based on the cancellation estimation signal.

[0013] According to this aspect, the control device generates a correction signal using a correction filter (a filter that indicates the difference between the acoustic characteristics at the position of the error microphone and the acoustic characteristics at the position of the user), corrects the error signal using the correction signal to generate a corrected error signal, and adaptively updates the control filter based on the corrected error signal. This makes it possible to perform noise reduction control that follows the change in the user's position, thereby improving the noise reduction effect at the user's position. Furthermore, the control device generates a corrected reference signal based on the reference signal using the secondary path filter and the correction filter, and adaptively updates the control filter based on the corrected reference signal. This makes it possible to adaptively update the control filter more accurately. Furthermore, the control device adaptively updates the secondary path filter based on the cancellation estimation signal. This makes it possible to perform noise reduction control that follows the change in the transfer function of the secondary path, thereby further improving the noise reduction effect.

[0014] In the above aspect, the control device generates a virtual error signal (e v ) and adaptively updating the secondary path filter so as to minimize the virtual error signal.

[0015] According to this aspect, the control device adaptively updates the secondary path filter based on the error signal, not on the corrected error signal. Therefore, the secondary path filter after adaptive updating converges to the transfer function of the secondary path from the speaker to the error microphone, not to the transfer function of the secondary path from the speaker to the passenger position. This makes it possible to accurately estimate the transfer function of the secondary path from the speaker to the error microphone, thereby improving the stability of the noise reduction control.

[0016] In order to solve the above problem, one aspect of the present invention is an active noise reduction device (121) including a speaker (21) that outputs a canceling sound to cancel noise, an error microphone (22) that generates an error signal (e) based on the noise and the canceling sound, and a control device (123) that controls the speaker based on the error signal, the control device including a control filter (W) that generates a control signal (u) for controlling the speaker, a secondary path filter (C^) that indicates an estimated value of a transfer function of a secondary path from the speaker to the error microphone, and a correction filter (ΔW, K) that indicates a difference between acoustic characteristics at the position of the error microphone and acoustic characteristics at the position of a user, and a corrected control signal (u) is generated by correcting the control signal with the correction filter. ear ), outputting the correction control signal to the speaker, generating a cancellation estimation signal (ŷ) based on the correction control signal by the secondary path filter, and adaptively updating the secondary path filter based on the cancellation estimation signal.

[0017] According to this aspect, the control device generates a correction control signal using a correction filter (a filter that indicates the difference between the acoustic characteristics at the position of the error microphone and the acoustic characteristics at the position of the user) and outputs the correction control signal to the speaker. This allows noise reduction control to be performed in accordance with changes in the position of the user, thereby improving the noise reduction effect at the position of the user. In addition, the control device adaptively updates the secondary path filter based on the cancellation estimation signal. This allows noise reduction control to be performed in accordance with changes in the transfer function of the secondary path, thereby further improving the noise reduction effect.

[0018] In the above aspect, the control device may generate a corrected error signal (e') by removing a component of the corrective filter from the error signal, and adaptively update the control filter based on the corrected error signal.

[0019] According to this aspect, it is possible to prevent the value of the control filter after adaptive updating from deviating from the original value due to the correction filter component included in the error signal, so that the adaptive updating of the control filter can be performed more accurately.

[0020] In the above aspect, the control device may further include a primary path filter indicating an estimate of a transfer function of a primary path from a noise source to the error microphone, and the correction filter may correspond to both the primary path filter and the secondary path filter.

[0021] According to this aspect, it is possible to achieve a noise reduction effect similar to that achieved by using a single correction filter in combination with a correction filter corresponding to the primary path filter and a correction filter corresponding to the secondary path filter, and it is also possible to save memory capacity of the control device compared to a case in which a correction filter corresponding to the primary path filter and a correction filter corresponding to the secondary path filter are separately provided. Effect of the Invention

[0022] According to the above aspects, it is possible to provide an active noise reduction device that can improve the noise reduction effect by performing noise reduction control that follows not only changes in the user's position but also changes in the transfer function of the secondary path. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is a schematic diagram showing a vehicle to which an active noise reduction device according to a first embodiment is applied; [Diagram 2] FIG. 1 is a functional block diagram showing an active noise reduction device according to a first embodiment; [Diagram 3] FIG. 1 is an explanatory diagram illustrating a method for calculating a correction filter according to a first embodiment; [Figure 4] FIG. 11 is an explanatory diagram showing a difference between a transfer function of a microphone secondary path and a transfer function of an occupant secondary path according to the first embodiment; [Diagram 5] FIG. 11 is a functional block diagram showing an active noise reduction device according to a second embodiment. [Figure 6] FIG. 11 is an explanatory diagram illustrating a method for calculating a first correction filter according to a second embodiment; [Figure 7] A functional block diagram showing an active noise reduction device according to a third embodiment. [Figure 8] A functional block diagram showing an active noise reduction device according to a fourth embodiment. [Figure 9] FIG. 13 is an explanatory diagram illustrating a method for identifying a correction filter according to a fourth embodiment; [Figure 10] FIG. 2 is a functional block diagram showing an active noise reduction device according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this specification, the "^" (hat) next to each symbol indicates an identified value or an estimated value. In the drawings, the "^" is placed above each symbol, but in the text, it is placed after each symbol.

[0025] (First embodiment) First, a first embodiment of the present invention will be described with reference to FIGS.

[0026] <Vehicle 3> 1 is a schematic diagram showing a vehicle 3 to which an active noise reduction device 1 (hereinafter, abbreviated as "noise reduction device 1") according to a first embodiment is applied. The vehicle 3 is, for example, a four-wheeled automobile.

[0027] A plurality of passenger seats 6 are arranged below a roof lining 5 within a passenger compartment 4 of a vehicle 3. Each passenger seat 6 (hereinafter simply referred to as a "passenger seat 6") has a seat cushion 7 and a reclining unit 8 that is arranged above and behind the seat cushion 7 and rotates relative to the seat cushion 7. The reclining unit 8 has a seat back 9 and a headrest 10 that is fixed to the upper end of the seat back 9.

[0028] <Noise reduction device 1> The noise reduction device 1 is an ANC device (Active Noise Control Device) for reducing noise d generated in a passenger compartment 4 of a vehicle 3. More specifically, the noise reduction device 1 generates a canceling sound y that is in the opposite phase to the noise d, and reduces the noise d by causing the generated canceling sound y to interfere with the noise d.

[0029] For example, the noise d to be reduced by the noise reduction device 1 is road noise caused by vibration of the wheels 15 due to a force from the road surface S. Note that the noise d to be reduced by the noise reduction device 1 may be noise other than the above-mentioned road noise (for example, drive system noise caused by vibration of a drive source such as an internal combustion engine or an electric motor).

[0030] 1 and 2, the noise reduction device 1 includes a plurality of speakers 21 that output a canceling sound y for canceling a noise d, a plurality of error microphones 22 that generate an error signal e based on the noise d and the canceling sound y, and a control device 23 that controls the plurality of speakers 21 based on the error signal e.

[0031] <Speaker 21> 1, each speaker 21 (hereinafter simply referred to as "speaker 21") is provided in a headrest 10 of reclining portion 8 of passenger seat 6. In other embodiments, speaker 21 may be provided in a portion of reclining portion 8 of passenger seat 6 other than headrest 10 (e.g., seat back 9), or may be provided in a portion of passenger seat 6 other than reclining portion 8. Furthermore, in other embodiments, speaker 21 may be provided in a portion of vehicle 3 other than passenger seat 6.

[0032] <Error Mic 22> Each error microphone 22 (hereinafter simply referred to as "error microphone 22") is provided in the headrest 10 of the reclining portion 8 of the passenger seat 6. In other embodiments, the error microphone 22 may be provided in a portion of the reclining portion 8 of the passenger seat 6 other than the headrest 10 (for example, the seat back 9), or may be provided in a portion of the passenger seat 6 other than the reclining portion 8. Furthermore, in other embodiments, the error microphone 22 may be provided in a portion of the vehicle 3 other than the passenger seat 6.

[0033] C in FIG. 2 shows a transfer function of a secondary path from the speaker 21 to the error microphone 22 (hereinafter referred to as a “microphone secondary path”). ear 2 indicates the transfer function of the secondary path from the speaker 21 to the ear position of the occupant (an example of a user) (hereinafter referred to as the "occupant secondary path"). P in FIG. 2 indicates the transfer function of the primary path from the noise source to the error microphone 22 (hereinafter referred to as the "microphone primary path"). ear indicates the transfer function of the primary path from the noise source to the position of the occupant's ear (hereinafter referred to as the "occupant primary path"). The transfer function C of the microphone secondary path and the transfer function P of the microphone primary path indicate the acoustic characteristics at the position of the error microphone 22, and the transfer function C of the occupant secondary path ear and the transfer function P of the primary passenger path ear indicates the acoustic characteristics at the position of the passenger's ears.

[0034] <Control device 23> The control device 23 is configured by a computer having an arithmetic processing unit (a processor such as a CPU or an MPU) and a storage device (a memory such as a ROM or a RAM). The control device 23 may be configured as a single piece of hardware, or may be configured as a unit consisting of multiple pieces of hardware.

[0035] The control device 23 acquires a reference signal r corresponding to the noise d. For example, the reference signal r is input to the control device 23 from an acceleration sensor (not shown) arranged on a suspension of the vehicle 3. In other embodiments, the reference signal r may be input to the control device 23 from a reference microphone (not shown) that generates the reference signal r from the noise d, or may be input to the control device 23 from a component other than the acceleration sensor or the reference microphone.

[0036] 2, the control device 23 has, as functional components, a control signal generating unit 31, a sound field learning unit 32, and an error signal correcting unit 33.

[0037] <Control signal generating unit 31> The control signal generating unit 31 of the control device 23 includes a control filter unit 41 , a secondary path filter unit 42 , and a control updating unit 43 .

[0038] The control filter unit 41 is configured by a control filter W. The control filter W is configured by, for example, an FIR filter (finite impulse response filter). In another embodiment, the control filter W may be configured by a SAN filter (single frequency adaptive notch filter) or the like.

[0039] The control filter unit 41 generates a control signal u for controlling the speaker 21 by performing filtering on the reference signal r using the control filter W. The control filter unit 41 outputs the generated control signal u to the speaker 21, the sound field learning unit 32, and the error signal correction unit 33. In response to this, the speaker 21 generates a cancellation sound y according to the control signal u output from the control filter unit 41.

[0040] The secondary path filter unit 42 is configured with a secondary path filter C^. The secondary path filter C^ is a filter that indicates an estimated value of a transfer function C of a microphone secondary path. The secondary path filter C^ is configured with, for example, an FIR filter. In other embodiments, the secondary path filter C^ may be configured with a SAN filter or the like.

[0041] The secondary path filter unit 42 generates a corrected reference signal r' by filtering the reference signal r using the secondary path filter C^. The secondary path filter unit 42 outputs the generated corrected reference signal r' to the control update unit 43.

[0042] The control update unit 43 calculates the corrected reference signal r′ output from the secondary path filter unit 42 and the corrected error signal e output from the error signal correction unit 33. ear (Details will be described later) and adaptively update the control filter W based on the above. More specifically, the control update unit 43 uses an adaptive algorithm such as an LMS algorithm (Least Mean Square Algorithm) to update the correction error signal e ear The control filter W is adaptively updated so that

[0043] <Sound Field Learning Section 32> The sound field learning unit 32 of the control device 23 has a canceling sound estimation signal generation unit 51, a secondary path update unit 52, a noise estimation signal generation unit 53, a primary path update unit 54, a canceling sound estimation signal inversion unit 55, a noise estimation signal inversion unit 56, and an adder 57.

[0044] The canceling sound estimation signal generation unit 51 is configured with the secondary path filter C^, similar to the secondary path filter unit 42. When the secondary path filter C^ is updated in the canceling sound estimation signal generation unit 51, the updated secondary path filter C^ is output to the secondary path filter unit 42, and the secondary path filter C^ is updated in the secondary path filter unit 42. In other words, the secondary path filter C^ set in the secondary path filter unit 42 is not a fixed value, but a value that is successively updated based on the signal from the canceling sound estimation signal generation unit 51.

[0045] The cancellation sound estimation signal generating unit 51 generates a cancellation sound estimation signal y^ indicating an estimated value of the cancellation sound y by performing a filtering process on the control signal u using the secondary path filter C^. The cancellation sound estimation signal generating unit 51 outputs the generated cancellation sound estimation signal y^ to the cancellation sound estimation signal inverting unit 55.

[0046] The secondary path update unit 52 receives the control signal u output from the control filter unit 41 and the virtual error signal e output from the adder 57. v (Details will be described later) and adaptively update the secondary path filter Ĉ based on the above. More specifically, the secondary path update unit 52 adaptively updates the virtual error signal e v The secondary path filter Ĉ is adaptively updated so that Ĉ is minimized.

[0047] The noise estimation signal generator 53 is configured with a primary path filter P^. The primary path filter P^ is a filter that indicates an estimated value of a transfer function P of the microphone primary path. The primary path filter P^ is configured with, for example, an FIR filter. In other embodiments, the primary path filter P^ may be configured with a SAN filter or the like.

[0048] The noise estimation signal generation unit 53 generates a noise estimation signal d^ indicating an estimated value of the noise d by filtering the reference signal r with the primary path filter P^. The noise estimation signal generation unit 53 outputs the generated noise estimation signal d^ to the noise estimation signal inversion unit 56.

[0049] The primary path update unit 54 receives the reference signal r and the virtual error signal e output from the adder 57. v (Details will be described later) and adaptively update the primary path filter P̂ based on the above. More specifically, the primary path update unit 54 adaptively updates the virtual error signal e v The primary path filter P̂ is adaptively updated so that

[0050] The canceling sound estimation signal inverting unit 55 inverts the polarity of the canceling sound estimation signal y^ output from the canceling sound estimation signal generating unit 51. The canceling sound estimation signal inverting unit 55 outputs the canceling sound estimation signal y^ with the polarity inverted to the adder 57.

[0051] The noise estimation signal inverting unit 56 inverts the polarity of the noise estimation signal d^ output from the noise estimation signal generating unit 53. The noise estimation signal inverting unit 56 outputs the noise estimation signal d^ with the polarity inverted to the adder 57.

[0052] The adder 57 outputs the cancellation estimation signal y^ passed through the cancellation estimation signal inverting unit 55, the noise estimation signal d^ passed through the noise estimation signal inverting unit 56, and the corrected error signal e output from the error signal correcting unit 33. ear (Details will be described later) and are added together to obtain the virtual error signal e v The adder 57 generates the virtual error signal e v to the secondary route update unit 52 and the primary route update unit 54.

[0053] <Error signal correction unit 33> The error signal correction unit 33 of the control device 23 includes a correction filter unit 61 and an adder 62 .

[0054] The correction filter unit 61 is configured by a correction filter ΔC^. The correction filter ΔC^ is a filter obtained by multiplying an estimated value of the transfer function C of the microphone secondary path and a transfer function C of the passenger secondary path by ear ^ is a filter that indicates the difference between the estimated value of the error microphone 22 and the estimated value of the error microphone 22. That is, the correction filter ΔC^ is a filter that corresponds to the secondary path filter C^ and is a filter that indicates the difference between the acoustic characteristics at the position of the error microphone 22 and the acoustic characteristics at the position of the passenger's ear. The correction filter ΔC^ is, for example, configured by an FIR filter. In other embodiments, the correction filter ΔC^ may be configured by a SAN filter or the like. The correction filter ΔC^ is a fixed value calculated in advance.

[0055] The correction filter unit 61 performs filtering on the control signal u using the correction filter ΔĈ to generate a correction signal x. The correction filter unit 61 outputs the generated correction signal x to the adder 62.

[0056] The adder 62 adds the error signal e output from the error microphone 22 (the error signal at the position of the error microphone 22) and the correction signal x output from the correction filter unit 61 to generate a corrected error signal e ear That is, the adder 62 corrects the error signal e using the correction signal x to generate a corrected error signal e ear The adder 62 generates the corrected error signal e ear to the control signal generating unit 31 and the sound field learning unit 32.

[0057] <Calculation method of correction filter ΔC^> Next, an example of a method for calculating the correction filter ΔC^ will be described with reference to Fig. 3. When calculating the correction filter ΔC^, a first measurement microphone 71 is installed at a position corresponding to the ear position of the occupant, a second measurement microphone 72 is installed at a position corresponding to the error microphone 22, and a measurement speaker 73 is installed at a position corresponding to the speaker 21.

[0058] First, an identification sound signal i is input from the signal input device 74 to the measurement speaker 73, so that the measurement speaker 73 outputs an identification sound (for example, white noise). In this state, the identification sound signal i and the occupant noise canceling signal y measured by the first measurement microphone 71 are ear and the microphone cancellation signal y measured by the second measurement microphone 72. m and are recorded in the signal recording unit 75.

[0059] Next, the identification sound signal i and the occupant cancellation signal y recorded in the signal recording unit 75 are ear , and the microphone mute signal y m Based on this, the transfer function C of the passenger secondary path is calculated by a learning process using an adaptive algorithm. ear and an estimate of the transfer function C of the microphone secondary path. ear The compensation filter ΔC^ is calculated by subtracting the estimated value of the transfer function C of the microphone secondary path from the estimated value of . The compensation filter ΔC^ is expressed by the following equation (1).

number

[0060] <Action and effect> The error signal e is a signal generated by adding the cancellation sound y and the noise d together. Therefore, the error signal e is expressed by the following equation (2).

number

number

number

number

[0061] From the above equation (5), the correction error signal e ear is an estimate of the sound pressure at the passenger's ear position after noise reduction control. Therefore, the corrected error signal e ear By adaptively updating the control filter W so as to minimize , the estimated value of the sound pressure after noise reduction control at the position of the passenger's ears is also minimized. This makes it possible to effectively reduce the noise d at the position of the passenger's ears.

[0062] 4, in this embodiment, the speaker 21 and the error microphone 22 are both disposed in the headrest 10 of the passenger seat 6, so that the distance from the speaker 21 to the error microphone 22 is short. ear Therefore, the control device 23 uses a correction filter ΔC^ to calculate the transfer function C of the microphone secondary path and the transfer function C of the passenger secondary path. ear This compensates for the difference between the noise level and the position of the passenger's ears, thereby improving the noise reduction effect.

[0063] On the other hand, when noise d occurs, the entire vehicle interior 4 vibrates due to the input from the road surface S. In this relationship, if the distance from the speaker 21 to the error microphone 22 is short, the transfer function P of the microphone primary path and the transfer function P of the occupant primary path ear Therefore, the control device 23 does not include a correction filter corresponding to the primary path filter P^, and the transfer function P of the microphone primary path and the transfer function P of the occupant primary path are ear This does not correct the difference between the microphone secondary path transfer function C and the passenger secondary path transfer function C ear The difference between the microphone primary path transfer function P and the passenger primary path transfer function P ear In comparison with the case where both the difference between and are corrected, the calculation load on the control device 23 can be reduced.

[0064] <Modification> In the first embodiment, the position of the occupant's ears is taken as the position of the occupant. In other embodiments, the position of the occupant may be the head position of the occupant, the seating position of the occupant, or the like. In other words, the position of the occupant is determined by the above-mentioned occupant noise canceling signal y ear Any position may be used as long as it is possible to measure the above.

[0065] In the first embodiment, the correction filter ΔC^ (a filter that indicates the difference between the acoustic characteristics at the position of the error microphone 22 and the acoustic characteristics at the position of the passenger's ear) is calculated by using the estimated value of the transfer function C of the microphone secondary path and the transfer function C of the passenger secondary path. ear A filter is used to show the difference between the estimated value ofear In another embodiment, the correction filter ΔC^ is a function of the transfer function C of the occupant secondary path relative to the estimated value of the transfer function C of the microphone secondary path. ear A filter that indicates the ratio of the estimated values ​​of may be used (ΔC^=C ear ^ / C^).

[0066] <Second embodiment> Next, an active noise reduction device 81 according to a second embodiment of the present invention (hereinafter, abbreviated as "noise reduction device 81") will be described with reference to Figures 5 and 6. Note that components other than an error signal correction unit 84 of a control device 83 are similar to those in the first embodiment, so the same reference numerals as in the first embodiment are used in the drawings and descriptions thereof will be omitted.

[0067] <Error signal correction unit 84> The error signal correction unit 84 of the control device 83 has a first correction filter unit 86 , a second correction filter unit 87 , and an adder 88 .

[0068] The first correction filter unit 86 is configured by a first correction filter ΔP^. The first correction filter ΔP^ is a filter that is obtained by subtracting an estimated value of the transfer function P of the microphone primary path from a transfer function P of the passenger primary path. ear The first correction filter ΔP^ is a filter that indicates the difference between the estimated value of the error microphone 22 and the estimated value of the error microphone 22. That is, the first correction filter ΔP^ is a filter that corresponds to the primary path filter P^ and indicates the difference between the acoustic characteristics at the position of the error microphone 22 and the acoustic characteristics at the position of the passenger's ear. The first correction filter ΔP^ is, for example, configured by an FIR filter. In other embodiments, the first correction filter ΔP^ may be configured by a SAN filter or the like. The first correction filter ΔP^ is a fixed value that is set in advance.

[0069] The first correction filter unit 86 generates a first correction signal x1 by performing filtering on the reference signal r using the first correction filter ΔP^. The first correction filter unit 86 outputs the generated first correction signal x1 to the adder 88.

[0070] The second correction filter unit 87 is configured with a second correction filter ΔC^. The second correction filter ΔC^ is similar to the correction filter ΔC^ according to the first embodiment, and therefore a description thereof will be omitted. The second correction filter unit 87 generates a second correction signal x2 by filtering the control signal u using the second correction filter ΔC^. The second correction filter unit 87 outputs the generated second correction signal x2 to the adder 88.

[0071] The adder 88 adds together the error signal e output from the error microphone 22 (the error signal at the position of the error microphone 22), the first correction signal x1 output from the first correction filter unit 86, and the second correction signal x2 output from the second correction filter unit 87, to obtain a corrected error signal e ear That is, the adder 88 corrects the error signal e using the first correction signal x1 and the second correction signal x2 to generate a corrected error signal e ear The adder 88 generates the corrected error signal e ear to the control signal generating unit 31 and the sound field learning unit 32.

[0072] <Calculation method of the first correction filter ΔP^> Next, an example of a method for calculating the first correction filter ΔP^ will be described with reference to Fig. 6. When calculating the first correction filter ΔP^, a first measurement microphone 91 is installed at a position corresponding to the ear position of the occupant, a second measurement microphone 92 is installed at a position corresponding to the error microphone 22, and a reference signal output device 93 is installed at a position corresponding to the noise source. The reference signal output device 93 is, for example, an acceleration sensor installed on a suspension.

[0073] First, the vehicle 3 is driven to generate noise d (road noise). In this state, the passenger noise signal d measured by the first measuring microphone 91 is ear and a microphone noise signal d measured by the second measuring microphone 92. m and the reference signal r output from the reference signal output device 93 are recorded in the signal recording unit 94.

[0074] Next, the reference signal r and the passenger noise signal d recorded in the signal recording unit 94 are ear , and microphone noise signal d m Based on this, the transfer function P of the occupant primary path is calculated by a learning process using an adaptive algorithm. ear and an estimate of the transfer function P of the microphone primary path are calculated. Furthermore, the transfer function P of the passenger primary path is calculated. ear The first correction filter ΔP^ is calculated by subtracting the estimated value of the transfer function P of the microphone primary path from the estimated value of . The first correction filter ΔP^ is expressed by the following equation (6).

number

[0075] <Calculation method of the second correction filter ΔC^> The calculation method of the second correction filter ΔC^ is the same as the calculation method of the correction filter ΔC^ according to the first embodiment, and therefore the description will be omitted. The second correction filter ΔC^ is expressed by the above formula (1) like the correction filter ΔC^ according to the first embodiment.

[0076] <Action and effect> The error signal e is a signal generated by adding the cancellation sound y and the noise d together. Therefore, the error signal e is expressed by the following equation (7).

number

number

number

number

[0077] From the above equation (10), the correction error signal e ear is an estimate of the sound pressure at the passenger's ear position after noise reduction control. Therefore, the corrected error signal e ear By adaptively updating the control filter W so as to minimize , the estimated value of the sound pressure after noise reduction control at the position of the passenger's ears is also minimized. This makes it possible to effectively reduce the noise d at the position of the passenger's ears.

[0078] <Modification> In the above first embodiment, the error signal e is corrected using only the correction filter ΔC^ corresponding to the secondary path filter C^, and in the above second embodiment, the error signal e is corrected using the first correction filter ΔP^ corresponding to the primary path filter P^ and the second correction filter ΔC^ corresponding to the secondary path filter C^. In other embodiments, the error signal e may be corrected using only the correction filter ΔP^ corresponding to the primary path filter P^.

[0079] <Third embodiment> Next, an active noise reduction device 101 (hereinafter, abbreviated as "noise reduction device 101") according to a third embodiment of the present invention will be described with reference to Fig. 7. Note that, since the components other than the control device 103 are similar to those in the first embodiment, the same reference numerals as in the first embodiment are used in the drawing and the description will be omitted.

[0080] <Control device 103> The control device 103 has, as functional components, a control signal generating unit 104 and a sound field learning unit 105. The sound field learning unit 105 is similar to the sound field learning unit 32 according to the first embodiment, and therefore a description thereof will be omitted.

[0081] <Control signal generating unit 104> The control signal generating unit 104 of the control device 103 has a control filter unit 107, a reference signal correcting unit 108, an error signal correcting unit 109, and a control updating unit 110. The control filter unit 107 is similar to the control filter unit 41 according to the first embodiment, and therefore a description thereof will be omitted.

[0082] The reference signal correction unit 108 includes a secondary path filter unit 112 , a first correction filter unit 113 , and an adder 114 .

[0083] The secondary path filter unit 112 is configured with a secondary path filter C^. The secondary path filter C^ is similar to the secondary path filter C^ in the first embodiment, and therefore a description thereof will be omitted. The secondary path filter unit 112 generates a corrected reference signal r' by performing filtering on the reference signal r using the secondary path filter C^. The secondary path filter unit 112 outputs the generated corrected reference signal r' to the adder 114.

[0084] The first correction filter unit 113 is configured with a correction filter ΔC^. The correction filter ΔC^ is similar to the correction filter ΔC^ according to the first embodiment, and therefore a description thereof will be omitted. The first correction filter unit 113 generates a first correction signal x1 by performing a filtering process on the reference signal r using the correction filter ΔC^. The first correction filter unit 113 outputs the generated first correction signal x1 to the adder 114.

[0085] The adder 114 adds the corrected reference signal r′ output from the secondary path filter unit 112 and the first correction signal x1 output from the first correction filter unit 113 to obtain the corrected reference signal r x The adder 114 generates the corrected reference signal r x to the control update unit 110.

[0086] As described above, the reference signal correction unit 108 corrects the reference signal r using the secondary path filter C^ and the correction filter ΔC^ to obtain a corrected reference signal r x Generate.

[0087] The error signal correction unit 109 includes a second correction filter unit 116 and an adder 117 .

[0088] The second correction filter unit 116 is configured with a correction filter ΔC^, similar to the first correction filter unit 113. The second correction filter unit 116 generates a second correction signal x2 by performing filtering on the control signal u with the correction filter ΔC^. The second correction filter unit 116 outputs the generated second correction signal x2 to the adder 117.

[0089] The adder 117 adds the error signal e output from the error microphone 22 (the error signal at the position of the error microphone 22) and the second correction signal x2 output from the second correction filter unit 116 to obtain a corrected error signal e ear In other words, the adder 117 corrects the error signal e using the second correction signal x2 to generate a corrected error signal e ear The adder 117 generates the correction error signal e ear to the control update unit 110.

[0090] The control update unit 110 updates the corrected reference signal r x and the corrected error signal e output from the error signal corrector 109. ear In more detail, the control update unit 110 adaptively updates the control filter W based on the correction error signal e ear The control filter W is adaptively updated so that

[0091] <Adaptive updating of secondary path filter C^ and primary path filter P^> The adder 57 adds the cancellation estimation signal y^ passed through the cancellation estimation signal inverting unit 55, the noise estimation signal d^ passed through the noise estimation signal inverting unit 56, and the error signal e output from the error microphone 22 to generate a virtual error signal e. v The adder 57 generates the virtual error signal e v to the secondary route update unit 52 and the primary route update unit 54.

[0092] The secondary path update unit 52 receives the control signal u and the virtual error signal e v In more detail, the secondary path update unit 52 adaptively updates the secondary path filter Ĉ based on the virtual error signal e v The secondary path filter Ĉ is adaptively updated so that Ĉ is minimized.

[0093] The primary path update unit 54 calculates the reference signal r and the virtual error signal e v In more detail, the primary path update unit 54 adaptively updates the virtual error signal e v The primary path filter P̂ is adaptively updated so that

[0094] <Action and effect> Referring to FIG. 2, in the first embodiment described above, the control device 23 outputs a correction error signal e ear Based on the error signal at the passenger's ear position, a virtual error signal e v and generate a virtual error signal e v Therefore, the secondary path filter C^ after the adaptive update is the transfer function C of the passenger secondary path. ear Therefore, it may not be possible to accurately estimate the transfer function C of the microphone secondary path.

[0095] In contrast, referring to FIG. 7, in this embodiment, the control device 103 calculates a virtual error signal e based on the error signal e (the error signal at the position of the error microphone 22). v and generate a virtual error signal ev The secondary path filter C^ is adaptively updated based on the above. Therefore, the secondary path filter C^ after adaptive updating converges to the transfer function C of the microphone secondary path. Therefore, the transfer function C of the microphone secondary path can be accurately estimated, and the stability of the noise reduction control can be improved.

[0096] <Fourth embodiment> Next, an active noise reduction device 121 (hereinafter, abbreviated as "noise reduction device 121") according to a fourth embodiment of the present invention will be described with reference to Figures 8 and 9. Note that since the components other than the control device 123 are similar to those in the first embodiment, the same reference numerals as in the first embodiment are used in the figures and descriptions thereof will be omitted.

[0097] 8, the control device 123 has, as functional components, a control signal generating unit 124 and a sound field learning unit 125. The sound field learning unit 125 is similar to the sound field learning unit 32 according to the first embodiment, and therefore a description thereof will be omitted.

[0098] <Control signal generating unit 124> The control signal generating unit 124 of the control device 123 has a control filter unit 127, a secondary path filter unit 128, a control signal correcting unit 129, a component removing unit 130, and a control updating unit 131. The control filter unit 127 and the secondary path filter unit 128 are similar to the control filter unit 41 and the secondary path filter unit 42 according to the first embodiment, and therefore a description thereof will be omitted.

[0099] The control signal correction unit 129 is configured by a correction filter ΔW. The correction filter ΔW is expressed by the following equation (11).

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[0100] The control signal correction unit 129 performs filtering on the control signal u using the correction filter ΔW to generate a corrected control signal u ear In other words, the control signal correction unit 129 corrects the amplitude and phase of the control signal u using the correction filter ΔW to generate a corrected control signal u ear The control signal correction unit 129 generates the corrected control signal u ear to the speaker 21 and the sound field learning unit 125. In response to this, the speaker 21 receives the corrected control signal u ear A canceling sound y corresponding to the

[0101] The component removal unit 130 includes a removal filter unit 133 and an adder 134 .

[0102] The elimination filter unit 133 is configured with an elimination filter (1-ΔW)C^. The elimination filter (1-ΔW)C^ is configured with, for example, an FIR filter. In other embodiments, the elimination filter (1-ΔW)C^ may be configured with a SAN filter or the like.

[0103] The elimination filter unit 133 performs filtering on the control signal u using the elimination filter (1-ΔW)C^ to generate an elimination signal z. The elimination filter unit 133 outputs the generated elimination signal z to the adder .

[0104] The adder 134 generates a corrected error signal e' by adding together the error signal e output from the error microphone 22 and the cancellation signal z output from the cancellation filter unit 133. In other words, the adder 134 generates the corrected error signal e' by correcting the error signal e with the cancellation signal z. The adder 134 outputs the generated corrected error signal e' to the control update unit 131.

[0105] The control update unit 131 adaptively updates the control filter W based on the corrected reference signal r' output from the secondary path filter unit 128 and the corrected error signal e' output from the component removal unit 130. More specifically, the control update unit 131 adaptively updates the control filter W by using an adaptive algorithm such as an LMS algorithm, so that the corrected error signal e' is minimized.

[0106] <Adaptive updating of secondary path filter C^ and primary path filter P^> The cancellation estimation signal generator 51 generates a correction control signal u by the secondary path filter C^. ear The secondary path update unit 52 generates the cancellation estimation signal y^ by performing a filter process on the corrected control signal u ear and the virtual error signal e v In other respects, the method of adaptively updating the secondary path filter C^ and the primary path filter P^ according to the present embodiment is similar to the method of adaptively updating the secondary path filter C^ and the primary path filter P^ according to the third embodiment, and therefore a description thereof will be omitted.

[0107] <How to identify the correction filter ΔW> Next, an example of a method for identifying the correction filter ΔW will be described with reference to FIG.

[0108] First, a microphone noise signal d m and passenger noise signal d ear is recorded in the first signal recording unit 141. In addition, the microphone cancellation signal y m and occupant silencer signal y ear is recorded in the second signal recording unit 142.

[0109] Next, as shown in FIG. 9(a), the microphone noise signal d recorded in the first signal recording unit 141 is m and passenger noise signal d ear Based on the above, the primary path characteristic ΔP is identified. More specifically, the microphone noise signal d m and occupant noise signal d ear The primary path characteristic ΔP is adaptively updated so that the error signal e1 between

[0110] Next, as shown in FIG. 9(b), the microphone cancellation signal y m and occupant silencer signal y ear In more detail, the secondary path characteristic ΔC is used to identify the microphone cancellation signal y m and the occupant silencer signal y ear The secondary path characteristic ΔC is adaptively updated so that the error signal e2 between

[0111] 9(c), a correction filter ΔW is identified based on the identified primary path characteristic ΔP and secondary path characteristic ΔC. More specifically, the correction filter ΔW is adaptively updated so that an error signal e3 between an identified sound signal i (white noise, etc.) filtered using the secondary path characteristic ΔC and the correction filter ΔW and an identified sound signal i filtered using the primary path characteristic ΔP is minimized.

[0112] <Action and effect> The error signal e is a signal generated by adding the cancellation sound y and the noise d together. Therefore, the error signal e is expressed by the following equation (14).

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[0113] From the above formula (16), the following formula (17) is obtained.

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[0114] On the other hand, the speaker 21 is controlled by an equivalent filter W×ΔW obtained by multiplying a control filter W by a correction filter ΔW. This equivalent filter W×ΔW is expressed by the following equation (19).

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[0115] In addition, the control device 123 calculates a virtual error signal e based on the error signal e (the error signal at the position of the error microphone 22). v and generate a virtual error signal e v The secondary path filter C^ is adaptively updated based on the above. Therefore, the secondary path filter C^ after adaptive updating converges to the transfer function C of the microphone secondary path. Therefore, similarly to the third embodiment, the transfer function C of the microphone secondary path can be accurately estimated, and the stability of the noise reduction control can be improved.

[0116] <Modification> In the above fourth embodiment, the control signal correction unit 129 is configured by a correction filter ΔW (FIR filter) that corrects the amplitude and phase of the control signal u. With reference to Fig. 10, in another embodiment, the control signal correction unit 129 may be configured by a correction filter K (multiplier) that corrects only the amplitude of the control signal u. This makes it possible to save memory capacity of the control device 123 compared to the case where the control signal correction unit 129 is configured by the correction filter ΔW. Note that, when the control signal correction unit 129 is configured by the correction filter K, the elimination filter unit 133 is preferably configured by an elimination filter (1-K)C^ for removing the component of the correction filter K from the error signal e.

[0117] The correction filter K is a real number for adjusting the magnitude of the cancellation sound y. For example, when the correction filter K is set to 2, the cancellation sound y for controlling the noise d at the position of the error microphone 22 is amplified by a factor of two. The correction filter K, like the correction filter ΔW, is a filter that corresponds to both the primary path filter P^ and the secondary path filter C^, and indicates the difference between the acoustic characteristics at the position of the error microphone 22 and the acoustic characteristics at the position of the passenger's ear.

[0118] In the above first to fourth embodiments, the noise reduction devices 1, 81, 101, 121 are applied to the passenger compartment 4 of the vehicle 3. In other embodiments, the noise reduction devices 1, 81, 101, 121 may be applied to the interior space of a moving body other than the vehicle 3 (for example, a ship or an aircraft), and the noise reduction devices 1, 81, 101, 121 may be applied to the interior space of a fixed object (for example, a house).

[0119] Although the specific embodiment has been described above, the present invention is not limited to the above embodiment and its modified examples, and can be modified in a wide range of ways. [Explanation of symbols]

[0120] (First embodiment) 1: Active noise reduction device 21: Speaker 22: Error microphone 23: Control device W: Control filter P^: Primary path filter C^: Secondary path filter ΔC^ : Correction filter Second embodiment 81: Active noise reduction device 83: Control device ΔP^: First correction filter ΔC^: Second correction filter Third embodiment 101: Active noise reduction devices 103: Control device (Fourth embodiment) 121: Active noise reduction devices 123: Control device ΔW: Correction filter k : Correction filter

Claims

1. A speaker that outputs a canceling sound to cancel out noise; an error microphone for generating an error signal based on the noise and the cancellation sound; a control device that controls the speaker based on the error signal, The control device includes: a control filter that generates a control signal for controlling the speaker; a secondary path filter that indicates an estimate of a transfer function of a secondary path from the speaker to the error microphone; and a correction filter that indicates a difference between an acoustic characteristic at a position of the error microphone and an acoustic characteristic at a position of a user, generating a correction signal by the correction filter; generating a corrected error signal by correcting the error signal with the correction signal; Adaptively updating the control filter based on the corrected error signal; generating a cancellation estimation signal based on the control signal by the secondary path filter; An active noise reduction system that adaptively updates the secondary path filter based on the cancellation estimation signal and the corrected error signal.

2. The control device further comprises a primary path filter that indicates an estimate of a transfer function of a primary path from a noise source to the error microphone; The correction filter is a first correction filter corresponding to the primary path filter; 2. The active noise reduction system of claim 1, further comprising: a second corrective filter corresponding to said secondary path filter.

3. A speaker that outputs a canceling sound to cancel out noise; an error microphone for generating an error signal based on the noise and the cancellation sound; a control device that controls the speaker based on the error signal, The control device includes: a control filter that generates a control signal for controlling the speaker; a secondary path filter that indicates an estimate of a transfer function of a secondary path from the speaker to the error microphone; and a correction filter that indicates a difference between an acoustic characteristic at a position of the error microphone and an acoustic characteristic at a position of a user, generating a correction signal by the correction filter; generating a corrected error signal by correcting the error signal with the correction signal; obtaining a reference signal corresponding to the noise; generating a corrected reference signal based on the reference signal by the secondary path filter and the correction filter; Adaptively updating the control filter based on the corrected error signal and the corrected reference signal; generating a cancellation estimation signal based on the control signal by the secondary path filter; An active noise reduction system that adaptively updates the secondary path filter based on the cancellation estimation signal.

4. The control device includes: generating a virtual error signal based on the error signal and the cancellation estimation signal; 4. An active noise reduction system according to claim 3, wherein said secondary path filter is adaptively updated so as to minimize said virtual error signal.

5. A speaker that outputs a canceling sound to cancel out noise; an error microphone for generating an error signal based on the noise and the cancellation sound; a control device that controls the speaker based on the error signal, The control device includes: a control filter that generates a control signal for controlling the speaker; a secondary path filter that indicates an estimate of a transfer function of a secondary path from the speaker to the error microphone; and a correction filter that indicates a difference between an acoustic characteristic at a position of the error microphone and an acoustic characteristic at a position of a user, generating a corrected control signal by correcting the control signal with the correction filter; outputting the correction control signal to the speaker; generating a cancellation estimation signal based on the corrected control signal by the secondary path filter; An active noise reduction system that adaptively updates the secondary path filter based on the cancellation estimation signal.

6. The control device includes: generating a corrected error signal by removing a component of the correction filter from the error signal; 6. An active noise reduction system according to claim 5, wherein said control filter is adaptively updated based on said corrected error signal.

7. The control device further comprises a primary path filter that indicates an estimate of a transfer function of a primary path from a noise source to the error microphone; 7. The active noise reduction device according to claim 5, wherein the correction filter corresponds to both the primary path filter and the secondary path filter.

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