Audio reproduction device, signal processing device, signal processing method

Abstract

A sound reproducing device according to the present invention comprises: a first microphone which is used for a noise cancelling process that is carried out by a feedback method; a second microphone which is used for a noise cancelling process that is carried out by a feedback method and which has a sound collecting surface in a direction different from the direction of a sound collecting surface of the first microphone; and a sound signal processing section which uses a first sound collection signal obtained by sound collection by the first microphone and a second sound collection signal obtained by sound collection by the second microphone to generate a noise cancelling signal.

Description

Technical Field

[0001] The present disclosure relates to an acoustic playback device, a signal processing device, and a signal processing method. In particular, it relates to the generation of a noise cancellation signal.

Background Art

[0002] As disclosed in Patent Documents 1, 2, and 3 below, a noise cancellation system that reduces external environment noise (noise) in headphones and earphones used in portable audio players and the like to provide a good playback sound field space with reduced external noise to the listener is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] An example of this type of noise cancellation system is an active noise reduction system that performs active noise reduction and basically has the following configuration. That is, a microphone as an acoustic-electric conversion means collects external noise (noise), and a noise cancellation signal that is acoustically out of phase with the noise is generated from the acoustic signal of the collected noise. This noise cancellation signal is synthesized with an acoustic signal for the original listening purpose such as music and acoustically reproduced by a speaker. Thereby, external noise is acoustically canceled to reduce noise.

[0005] In such a noise reduction system, it is considered that the noise cancellation performance can be improved by using a plurality of microphones to collect sound and generating a noise cancellation signal through appropriate filtering processing.

[0006] In the present disclosure, assuming the case of using a plurality of microphones in this way, a more appropriate microphone arrangement state is proposed.

Means for Solving the Problem

[0007] The acoustic playback device of the present disclosure includes a first microphone used for noise cancellation processing by a feedback method, a second microphone having a sound collection surface in a direction different from that of the first microphone and used for noise cancellation processing by a feedback method, and an acoustic signal processing unit that generates a noise cancellation signal using a first sound collection signal collected by the first microphone and a second sound collection signal collected by the second microphone. In a configuration including a plurality of microphones for use in noise cancellation processing by a feedback method, it is easy to collect sound in a plurality of acoustic spaces inside the acoustic playback device.

[0008] In the above-described acoustic playback device, the sound collection surface of the first microphone may be located closer to the driver unit that performs acoustic output based on the noise cancellation signal than the sound collection surface of the second microphone. Thereby, the transfer function of the space from the driver unit to the sound collection surface of the first microphone is made less likely to change.

[0009] In the above-described acoustic playback device, the sound collection surface of the first microphone may be located facing the sound emission direction of the driver unit that performs acoustic output based on the noise cancellation signal. Thereby, the transfer function of the space from the driver unit to the sound collection surface of the first microphone is made less likely to change.

[0010] In the above-described acoustic playback device, a driver unit that performs acoustic output based on the noise cancellation signal is disposed, and a housing having a sound emission port from which the output sound from the driver unit is emitted is provided. The first microphone and the second microphone are disposed within the housing, and the second microphone may be positioned closer to the sound emission port than the first microphone. Thereby, the second microphone can collect sound closer to the eardrum than the first microphone.

[0011] In the above-described acoustic playback device, the sound collection surface of the second microphone may be positioned so as not to face the sound emission direction of the driver unit that performs acoustic output based on the noise cancellation signal. Thereby, it becomes easier for the second microphone to collect noise.

[0012] In the above-described acoustic playback device, at least one acoustic space is positioned within the housing in the sound emission direction of the driver unit, and the first microphone and the second microphone may be positioned within the one acoustic space. Thereby, it is possible to accurately collect the noise components in the acoustic space in which the microphone is disposed.

[0013] In the above-described acoustic playback device, the first microphone may be positioned such that the sound collection surface faces the sound emission direction of the driver unit, and the second microphone may be positioned such that the sound collection surface faces the same direction as the sound emission direction of the driver unit. Thereby, the transfer function of the space from the driver unit to the sound collection surface of the first microphone hardly changes. Also, the second microphone is made more likely to collect noise at a position closer to the eardrum.

[0014] In the above-described audio playback device, the first microphone and the second microphone may be arranged in different acoustic spaces. Thereby, the noises collected by the first microphone and the second microphone are made different.

[0015] In the above-described audio playback device, a plurality of acoustic spaces may be provided in the housing, and the first microphone and the second microphone may be located in different spaces among the plurality of acoustic spaces. Thereby, the noises collected by the first microphone and the second microphone are made more different.

[0016] In the above-described audio playback device, an acoustic resistance member that separates the first acoustic space in which the first microphone is located and the second acoustic space in which the second microphone is located may be arranged. Thereby, it is possible to make one acoustic space a stable space in which the transfer function of the space from the driver unit to the microphone hardly changes.

[0017] In the above-described audio playback device, a housing having a sound emission port through which output sound from a driver unit that performs audio output based on the noise cancellation signal is emitted is provided, and the first acoustic space is a space surrounded by the driver unit, the acoustic resistance member, and the housing, and the second acoustic space may be a space surrounded by the acoustic resistance member, the housing, and the sound emission port. Thereby, the first acoustic space is made a stable space in which the transfer function of the space hardly changes. Also, the second acoustic space is made a space in which it is easy to collect noise at a position closer to the eardrum.

[0018] In the above-described audio playback device, the first microphone may be located on the front side which is the sound emission direction of a driver unit that performs audio output based on the noise cancellation signal, and the second microphone may be located on the rear side of the driver unit. As a result, the second microphone located behind the driver unit can collect sound of the inverse phase of the acoustic output. Further, in the second microphone, the transfer function of the space from the driver unit to the sound collection surface of the second microphone is made less likely to change depending on the wearing state of the listener.

[0019] In the above-described acoustic reproducing apparatus, a first feedback filter that generates a first noise canceling signal based on a high-frequency component of the first sound collection signal, and a second feedback filter that generates a second noise canceling signal based on a low-frequency component of the second sound collection signal are provided, and the acoustic signal processing unit may generate the noise canceling signal based on the first noise canceling signal and the second noise canceling signal. Since the first microphone is arranged closer to the driver unit than the second microphone, the filter coefficient set in the first FB filter is less likely to be inappropriate than the filter coefficient set in the second FB filter. As a result, the noise canceling signal based on the first sound collection signal can be made less likely to generate howling than the noise canceling signal based on the second sound collection signal.

[0020] In the above-described acoustic reproducing apparatus, the high-frequency component of the first sound collection signal may be extracted by a high-pass filter, a high-shelving filter, or a high-peak EQ filter, and the low-frequency component of the second sound collection signal may be extracted by a low-pass filter, a low-shelving filter, or a low-peak EQ filter. As a result, for the feedback loop of the first microphone in which the transfer function of the space from the driver unit to the microphone is less likely to change, a sound collection signal of a high-frequency component that is likely to howl can be input. Also, for the feedback loop of the second microphone that is likely to collect noise at a position closer to the eardrum, a sound collection signal of a low-frequency component can be input.

[0021] In the above-described acoustic playback device, a third microphone used for noise cancellation processing by a feed-forward method is provided, and the acoustic signal processing unit may generate the noise cancellation signal using the first collected sound signal, the second collected sound signal, and a third collected sound signal collected by the third microphone. For example, it is conceivable to provide a third microphone so as to collect the sound outside the acoustic playback device.

[0022] The signal processing device of the present disclosure includes an acoustic signal processing unit that generates a noise cancellation signal using a first collected sound signal collected by a first microphone used for noise cancellation processing by a feedback method and a second collected sound signal collected by a second microphone having a sound collection surface in a direction different from that of the first microphone and used for noise cancellation processing by a feedback method.

[0023] The signal processing method of the present disclosure generates a noise cancellation signal using a first collected sound signal collected by a first microphone used for noise cancellation processing by a feedback method and a second collected sound signal collected by a second microphone having a sound collection surface in a direction different from that of the first microphone and used for noise cancellation processing by a feedback method. According to these signal processing devices and signal processing methods, in a configuration including a plurality of microphones for use in noise cancellation processing by a feedback method, it is easy to collect sound in a plurality of acoustic spaces inside the acoustic playback device.

Brief Description of the Drawings

[0024]

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Embodiments for Carrying Out the Invention

[0025] Hereinafter, the embodiments will be described in the following order. <1. Explanation of Noise Cancellation Technology> <2. First Embodiment> <2-1. Configuration of the Acoustic Playback Device> <2-2. Internal Structure of the Audio Reproduction Device> <2-3. Audio Reproduction Device as Headphones> <3. Second Embodiment> <3-1. Audio Reproduction Device as Earphones> <3-2. Audio Reproduction Device as Headphones> <4. Third Embodiment> <4-1. Audio Reproduction Device as Earphones> <4-2. Audio Reproduction Device as Headphones> <5. Fourth Embodiment> <5-1. Configuration of the Audio Reproduction Device> <5-2. Internal Structure of the Audio Reproduction Device> <6. Modification Examples> <6-1. First Modification Example> <6-2. Second Modification Example> <6-3. Others> <7. Summary> <8. This Technology> Note that the audio reproduction device described in the embodiments and claims refers to a device that a listener wears on the ear to listen, and includes not only a headset type (headphones) worn on the head, but also a type that is worn on the auricle or ear canal, so-called "earphones".

[0026] <1. Explanation of Noise Cancellation Technology> The noise cancellation technology of the feedback method will be explained. FIG. 1 is a block diagram showing a configuration example of an audio reproduction device to which a noise cancellation system of the feedback method is applied, from the viewpoint of the transfer function. Note that in FIG. 1, only the configuration of the part on one ear side of the listener (listener) of the audio reproduction device is shown. The configurations of the audio reproduction devices for both the left and right ears are the same as those in FIG. 1.

[0027] The audio reproduction device is provided with a driver unit as electro-acoustic conversion means for reproducing an acoustic signal that is an electrical signal. Then, a sound source signal Sm, which is a signal such as music that the listener wants to play, is supplied to a power amplifier as an output acoustic signal through an equalizer and an adder. The acoustic signal passing through the power amplifier is supplied to a driver unit, acoustically reproduced, and the reproduced sound is emitted to the listener's ear.

[0028] In the signal transmission path between the input terminal to which the sound source signal Sm is input and the driver units for the left and right ears, an equalizer, an adder, a power amplifier, a microphone, a microphone amplifier, and an FB (Feedback) filter for noise cancellation are provided. In such a configuration, in the listener's acoustic listening environment, among the noises outside the acoustic reproduction device, the noise N that enters the listener's acoustic listening position inside the acoustic reproduction device is reduced by a feedback method so that music can be listened to in a good environment.

[0029] In a feedback-type noise cancellation system, the noise at the acoustic synthesis position (noise cancellation point Pc) where the noise and the acoustic reproduction sound of the acoustic signal are synthesized at the listener's acoustic listening position is collected. Therefore, the microphone for noise collection is provided at a position where it can collect the noise at the noise cancellation point Pc inside the housing of the acoustic reproduction device. Since the sound at this microphone position becomes the control point, considering the noise attenuation effect, the noise cancellation point Pc is usually a position close to the ear, that is, the front surface of the diaphragm of the driver unit, and a microphone is provided at this position. Then, the inverted-phase component of the noise collected by the microphone is generated as a noise cancellation signal by the FB filter, and the generated noise cancellation signal is supplied to the driver unit for acoustic reproduction, thereby reducing the noise that has entered the housing of the acoustic reproduction device from the outside.

[0030] The analog acoustic signal collected by the microphone is converted into a digital acoustic signal by an ADC (Analog-to-digital Converter) through a microphone amplifier. Then, the digital acoustic signal is input to a digital filter (FB filter) for generating a feedback-type noise cancellation signal.

[0031] The digital filter generates a noise cancellation signal with characteristics corresponding to filter coefficients as parameters set thereto from the input digital acoustic signal.

[0032] The generated noise cancellation signal is supplied to an adder.

[0033] As described above, a sound source signal Sm that the listener wants to listen to is supplied to the adder through an equalizer. The equalizer corrects the sound quality of the input acoustic signal. The output of this equalizer and the noise cancellation signal from the FB filter are combined in the adder and supplied to a driver unit through a power amplifier as an output acoustic signal for acoustic reproduction. Note that a DAC (Digital-to-Analog Converter) for converting each signal from a digital signal to an analog signal is provided either before or after the adder.

[0034] The reproduced sound includes an acoustic reproduction component by the noise cancellation signal generated in the FB filter. The acoustic reproduction component by this noise cancellation signal and the noise are acoustically combined, so that the noise is reduced (cancelled) at the noise cancellation point Pc.

[0035] Figure 1 shows the transfer functions of each part. Specifically, "A" represents the transfer function of the power amplifier, "D" represents the transfer function of the driver unit, "M" represents the transfer function corresponding to the microphone and microphone amplifier parts, and "-β" represents the transfer function of the filter designed for feedback. Also, "H" represents the transfer function of the space from the driver unit to the microphone, and "E" represents the transfer function of the equalizer applied to the sound source signal Sm for listening purposes. It is assumed that each of the above transfer functions is represented in complex form.

[0036] In addition, "N" shown in Figure 1 is the noise that has entered the vicinity of the microphone position inside the housing of the sound reproduction device from an external noise source, and "P" is the sound pressure reaching the listener's ear. As for the reason why external noise is transmitted into the housing of the sound reproduction device, for example, it may be the case where it leaks as sound pressure through the gap of the earpad part, or the case where sound is transmitted into the housing of the sound reproduction device as a result of the sound reproduction device vibrating in response to sound pressure.

[0037] The transfer function block in this Figure 1 can be expressed by the following (Equation 1).

[0038] (Equation 1) P = {1 / (1 + ADHMβ)}·N + {AHD / (1 + ADHMβ)}·ES

[0039] And, in this (Equation 1), focusing on the noise, it can be seen that the noise N is attenuated by 1 / (1 + ADHMβ). However, in order for the system of (Equation 1) to operate stably as a noise cancellation mechanism in the noise reduction target frequency band, the following (Equation 2) needs to hold.

[0040] (Equation 2) |1 / (1 + ADHMβ)| < 1

[0041] By setting the filter coefficient of the FB filter so that "-β" satisfies the above (Equation 2), a sufficient noise reduction effect can be obtained.

[0042] <2. First Embodiment> <2-1. Configuration of Audio Reproduction Device> A first embodiment of the audio reproduction device 1 will be described with reference to FIG. 2. Note that FIG. 2 shows the audio reproduction device 1 as an earphone as an example.

[0043] The audio reproduction device 1 includes a housing 3 in which an internal space 2 is formed, and a driver unit 4 disposed in the internal space 2.

[0044] The driver unit 4 is capable of acoustic output by including a diaphragm 4a. In the following description, the sound emission direction of the driver unit 4 is described as "front".

[0045] The housing 3 includes a box-shaped portion 5 having a cylindrical shape with the front-rear direction as the axial direction and formed in a box shape opened forward, and a sound guide tube 6 formed in a tubular shape extending forward from the opening in front of the box-shaped portion 5. The internal space 2 of the housing 3 includes an arrangement space 7 that is a space surrounded by the box-shaped portion 5 and in which each part such as the driver unit 4 is arranged, and a sound guide space 8 that is a space surrounded by the sound guide tube 6.

[0046] The opening in front of the sound guide tube 6 is formed as a sound emission port 9 for outputting the acoustic output from the driver unit 4 to the outside of the housing 3.

[0047] The driver unit 4 is disposed, for example, at a substantially central portion in the front-rear direction in the arrangement space 7. The arrangement space 7 is separated by the driver unit 4 into a front space 7a that is a space in front of the driver unit 4 and a rear space 7b that is a space behind the driver unit 4.

[0048] In the rear space 7b, for example, a substrate or a battery for driving the driver unit 4 may be housed.

[0049] The audio playback device 1 has an earpiece 10 detachably attached from the front to the outer peripheral surface of the sound emission port 9 in the housing 3. The earpiece 10 is formed of an elastically deformable member such as silicon, rubber, or urethane.

[0050] The audio playback device 1 has a plurality of microphones disposed in the internal space 2. FIG. 2 shows an example in which the audio playback device 1 is provided with two microphones. Specifically, the audio playback device 1 includes a first microphone 11 and a second microphone 12 used for noise canceling processing by a feedback method.

[0051] The first microphone 11 is disposed in the front space 7a such that the sound collection surface 11a substantially faces the diaphragm 4a of the driver unit 4.

[0052] The second microphone 12 is disposed in the sound guiding space 8 such that the sound collection surface 12a faces in a direction different from that of the sound collection surface 11a of the first microphone 11. Specifically, the second microphone 12 is attached such that the sound collection surface 12a faces the central axis of the sound guiding tube 6. In other words, the second microphone 12 is disposed so as not to face the diaphragm 4a of the driver unit 4.

[0053] That is, the first microphone 11 is disposed at a position closer to the driver unit 4 than the second microphone 12. Also, the second microphone 12 is disposed at a position closer to the sound emission port than the first microphone 11.

[0054] By disposing the first microphone 11 and the second microphone 12 in different acoustic spaces, it is possible to collect sound in the front space 7a and the sound guiding space 8, which are different acoustic spaces. That is, the first sound collection signal S1 of the first microphone 11 is a signal including noise in the front space 7a. Also, the second sound collection signal S2 of the second microphone 12 is a signal including noise in the sound guiding space 8.

[0055] Also, the second microphone 12 can collect sound at a position closer to the eardrum of the ear than the first microphone 11.

[0056] By adopting the above configuration, feedback control is performed using the sound collection signals collected from the first microphone 11 and the second microphone 12, and a noise cancellation signal is generated. The generated noise cancellation signal is, for example, added to the sound source signal Sm, and is generated as an output signal from the driver unit 4. When the output signal generated in this way is output from the driver unit 4, the reproduced sound with reduced noise at a predetermined cancellation point is listened to by the listener.

[0057] <2-2. Internal Configuration of the Acoustic Reproduction Device> FIG. 3 is a block diagram of the internal configuration of the acoustic reproduction device 1. In FIG. 3 and each subsequent figure, for the sake of simplicity of explanation, only one of the left and right channels of the stereo audio signal is shown. By adopting the same configuration as in FIG. 3 for the other channel, it is possible to perform noise cancellation processing for stereo sound. Note that each component part may be shared between the left and right channels.

[0058] A sound source signal Sm as a digital signal is input to the acoustic reproduction device 1 from a music / audio source device such as an audio player (not shown) provided outside. The sound source signal Sm is, for example, a digital signal such as music that the listener wants to listen to.

[0059] The acoustic reproduction device 1 includes, as each part for processing the first sound collection signal S1 of the first microphone 11, a first amplifier 21A, a first ADC 22A, and a first DSP (Digital Signal Processor) 23A.

[0060] The acoustic playback device 1 also includes, as components for processing the sound collection signal S2 of the second microphone 12, a second amplifier 21B, a second ADC 22B, and a second DSP 23B.

[0061] Furthermore, the acoustic playback device 1 includes adders 24, 25, an equalizer circuit 26, a DAC 27, and a power amplifier 28.

[0062] As described above, the first sound collection signal S1 is a sound that collects the sound including the noise in the front space 7a of the diaphragm 4a of the driver unit 4. The first sound collection signal S1 is amplified by the first amplifier 21A, then converted into a digital signal by the first ADC 22A, and input to the first DSP 23A.

[0063] The first DSP 23A includes a digital filter for generating a feedback-type noise cancellation signal.

[0064] FIG. 4 is a diagram showing a configuration example of the first DSP 23A. As shown in the figure, the first DSP 23A includes an HPF (High Pass Filter) 31 and a first FB filter 32.

[0065] The HPF 31 is a digital filter that removes the low-frequency components from the input digital signal from the first ADC 22A.

[0066] The first FB filter 32 is a digital filter for generating a feedback-type digital noise cancellation signal. That is, the first FB filter 32 generates a first noise cancellation signal Snc1 based on the high-frequency components in the first sound collection signal S1.

[0067] The signal generated by the first DSP 23A is input to the adder 24.

[0068] As described above, the second sound collection signal S2 is a sound that collects the sound including the noise in the sound guide space 8 which is the internal space of the sound guide tube 6. After the second audio signal S2 is amplified by the second amplifier 21B, it is converted into a digital signal by the second ADC 22B and input to the second DSP 23B.

[0069] The second DSP 23B is provided with a digital filter for generating a feedback-type noise canceling signal.

[0070] FIG. 5 is a diagram showing a configuration example of the second DSP 23B. As shown, the second DSP 23B includes an LPF (Low Pass Filter) 33 and a second FB filter 34.

[0071] The LPF 33 is a digital filter that removes high-frequency components from the input digital signal from the second ADC 22B.

[0072] The second FB filter 34 is a digital filter for generating a feedback-type digital noise canceling signal. That is, the second FB filter 34 generates a second noise canceling signal Snc2 based on the low-frequency components in the second audio signal S2.

[0073] The signal generated by the second DSP 23B is input to the adder 24.

[0074] The adder 24 adds and synthesizes the first noise canceling signal Snc1 generated based on the first audio signal S1 of the first microphone 11 and the second noise canceling signal Snc2 generated based on the second audio signal S2 of the second microphone 12, and outputs the synthesized noise canceling signal Snc to the adder 25.

[0075] In addition to the synthesized noise canceling signal Snc, a digital signal based on the sound source signal Sm is also input to the adder 25.

[0076] The sound source signal Sm is input to the equalizer circuit 26. The equalizer circuit 26 performs equalizing processing for sound quality correction processing and sound quality effect processing on the input sound source signal Sm, and outputs the obtained digital signal to the adder 25. The equalizer circuit 26 may be configured, for example, within the DSP.

[0077] The adder 25 adds and synthesizes the synthesized noise canceling signal Snc and the signal from the equalizer circuit 26, and outputs it to the DAC 27 as an output acoustic signal.

[0078] The output signal from the adder 25 is converted into an analog signal by the DAC 27, amplified by the power amplifier 28, and supplied to the driver unit 4.

[0079] In the driver unit 4, acoustic output processing based on the input output acoustic signal is executed. As a result, the reproduced sound with reduced noise at a predetermined noise canceling point is in a state where it can be listened to by the listener.

[0080] As shown in FIG. 2, the first microphone 11 is arranged such that the sound collecting surface 11a faces the diaphragm 4a of the driver unit 4. By arranging the first microphone 11 in this way, the transfer function of the space from the driver unit 4 to the first microphone 11 is made less likely to change.

[0081] If the transfer function of the space does not change, it is possible to generate a noise canceling signal having sufficient noise canceling performance with the filter coefficients set in the set first FB filter 32. That is, the first noise canceling signal Snc1 generated using the first sound collecting signal S1 is considered to be able to sufficiently exhibit noise canceling performance.

[0082] As shown in FIG. 2, the second microphone 12 is provided in the sound guiding space 8, and the transfer function of the space from the driver unit 4 to the second microphone 12 can change.

[0083] When the transfer function of the space changes, the filter coefficients set in the second FB filter 34 may become inappropriate, and in that case, howling may occur.

[0084] The occurrence of howling generally often results from high-frequency components of 1 kHz or more. Therefore, for high-frequency components, the first noise cancellation signal Snc1 generated using the first microphone 11, for which the transfer function of the space hardly changes, will be used. Thereby, the occurrence of howling caused by high-frequency components can be suppressed.

[0085] Also, for other low-frequency components, the second noise cancellation signal Snc2 generated using the second microphone 12 that can collect sound at a position closer to the eardrum of the listener will be used. Thereby, it becomes possible to bring the cancellation point closer to the eardrum.

[0086] For example, the first noise cancellation signal Snc1 is generated based on the high-frequency components of the first sound collection signal S1 extracted by the HPF 31 with a cut-off frequency of 200 Hz. Also, the second noise cancellation signal Snc2 is generated based on the low-frequency components of the second sound collection signal S2 extracted by the LPF 33 with a cut-off frequency of 200 Hz.

[0087] According to the above configuration, since the first noise cancellation signal Snc1 based on the high-frequency components of the first sound collection signal S1 and the second noise cancellation signal Snc2 based on the low-frequency components of the second sound collection signal S2 are synthesized to generate the synthesized noise cancellation signal Snc, it is possible to improve the noise cancellation performance at the eardrum position while suppressing the occurrence of howling.

[0088] In FIG. 3, an example in which the first DSP 23A and the second DSP 23B are provided is shown. However, a digital filter for the first sound collection signal S1 and a digital filter for the second sound collection signal S2 may be formed in one DSP. Also, in that case, an equalizer circuit 26 may be formed in the same DSP.

[0089] In FIG. 3, an example in which the sound source signal Sm is a digital signal is shown. However, it may be an analog signal. In that case, the sound source signal Sm is converted into a digital signal using an ADC and input to the equalizer circuit 26.

[0090] The HPF 31 included in the first DSP 23A can be substituted with a high-shelving filter or a high-peak EQ (equalizer) filter (see FIG. 19). Also, the LPF 33 included in the second DSP 23B can be substituted with a low-shelving filter or a low-peak EQ filter (see FIG. 19).

[0091] Note that the internal configuration of the sound reproduction device 1 may be other than the configurations shown in FIGS. 3, 4, and 5. For example, at least one of the first FB filter 32 and the second FB filter 34 may be a filter for an analog signal. In that case, the first ADC 22A and the second ADC 22B become unnecessary.

[0092] Also, instead of the first DSP 23A and the second DSP 23B, a CPU (Central Processing Unit) or a hard-wired circuit that performs hard-wired signal processing may be used.

[0093] Furthermore, the first microphone 11 and the second microphone 12 may be digital microphones. In that case, the first ADC 22A and the second ADC 22B become unnecessary.

[0094] Further, the HPF 31 shown in FIG. 4 may be provided not at the front stage but at the rear stage of the first FB filter 32. Further, the HPF 31 may be provided inside the first FB filter 32. Similarly, the LPF 33 shown in FIG. 5 may be provided at the rear stage of the second FB filter 34 or may be provided inside the second FB filter 34. The same applies to each of the subsequent parts.

[0095] <2-3. Acoustic playback device as a headphone> An example in which the configuration in the above-described first embodiment is applied to an acoustic playback device 1A as a headphone will be described with reference to FIG. 6. Note that the same components as those of the acoustic playback device 1 as an earphone shown in FIG. 2 are denoted by the same reference numerals.

[0096] The acoustic playback device 1A includes a housing 3 in which an internal space 2 is formed, and a driver unit 4 disposed in the internal space 2.

[0097] The driver unit 4 is capable of acoustic output by including a diaphragm 4a.

[0098] The housing 3 includes a base portion 42 in which a mounting recess 41 for mounting the driver unit 4 is formed, and an ear pad 43 attached to the peripheral edge in front of the mounting recess 41. The inner peripheral edge in front of the ear pad 43 is formed as a sound emission port 9.

[0099] The internal space 2 includes a front space 7a that is a space surrounded by the ear pad 43, the front surface of the driver unit 4, and the sound emission port 9, and a rear space 7b that is a space surrounded by the base portion 42 and the rear surface of the driver unit 4.

[0100] The acoustic playback device 1A includes a first microphone 11 and a second microphone 12 used for noise canceling processing by a feedback method.

[0101] In front of the diaphragm 4a of the driver unit 4, a protective member 44 formed in a mesh shape, for example, is attached to protect the diaphragm 4a.

[0102] The protective member 44 is provided with a first attachment portion 44a to which the first microphone 11 is attached and a second attachment portion 44b to which the second microphone 12 is attached, substantially at the center. The second microphone 12 is arranged such that the sound collection surface 12a faces a direction different from that of the sound collection surface 11a of the first microphone 11.

[0103] For example, the first attachment portion 44a is a recess opened rearward (in the direction of the diaphragm) and laterally, and the first microphone 11 is attached such that the sound collection surface 11a substantially faces the diaphragm 4a.

[0104] Also, the second attachment portion 44b is a recess opened forward and laterally, and the second microphone 12 is attached such that the sound collection surface 12a faces the same direction as the sound emission direction of the driver unit 4.

[0105] Both the first microphone 11 and the second microphone 12 are arranged in the front space 7a. That is, the first microphone 11 and the second microphone 12 are arranged in the same acoustic space. Since the first microphone 11 and the second microphone 12 are arranged in the same acoustic space, and the direction of the sound collection surface 11a of the first microphone 11 and the direction of the sound collection surface 12a of the second microphone 12 are different, it becomes possible to collect noise components in the acoustic space where the microphones are arranged with high precision. Therefore, it is possible to improve the noise cancellation performance.

[0106] Since the block diagram of the internal configuration of the acoustic reproduction device 1A has the same configuration as that in FIG. 3, the description is omitted.

[0107] By configuring the acoustic playback device 1A as a headphone as shown in FIGS. 3 and 6, a first noise canceling signal Snc1 based on the high-frequency component of the first sound collection signal S1 and a second noise canceling signal Snc2 based on the low-frequency component of the second sound collection signal S2 are synthesized to generate a synthesized noise canceling signal Snc. Therefore, it is possible to improve the noise canceling performance at the eardrum position while suppressing the occurrence of howling.

[0108] <3. Second Embodiment> <3-1. Acoustic Playback Device as an Earphone> The acoustic playback device 1B as an earphone in the second embodiment includes an acoustic resistance member 51 for dividing the internal space 2 into a plurality of acoustic spaces. The specific configuration will be described with reference to FIG. 7. Regarding the same configuration as that of the acoustic playback device 1 in the first embodiment shown in FIG. 2, the same reference numerals are given, and the description will be omitted as appropriate.

[0109] The acoustic playback device 1B includes a housing 3 in which an internal space 2 is formed, a driver unit 4 disposed in the internal space 2, a first microphone 11, and a second microphone 12.

[0110] The internal space 2 is composed of an arrangement space 7 in which each part is arranged and an acoustic conduction space 8 surrounded by the acoustic conduction tube 6. The arrangement space 7 is composed of a front space 7a which is a space in front of the driver unit 4 and a rear space 7b which is a space behind the driver unit 4.

[0111] The front opening of the acoustic conduction tube 6 is formed as a sound emission port 9 for outputting the acoustic output from the driver unit 4 to the outside of the housing 3.

[0112] The acoustic playback device 1B includes an acoustic resistance member 51 that separates the front space 7a and the acoustic conduction space 8 from each other. That is, the front space 7a is made into a space surrounded by the box-shaped part 5 of the housing 3, the driver unit 4, and the acoustic resistance member 51, thereby becoming an acoustically stable space. Therefore, the transfer function of the space from the driver unit 4 to the first microphone 11 is made less likely to change.

[0113] Also, the sound guide space 8 is made into a space surrounded by the sound guide tube 6 of the housing 3, the acoustic resistance member 51, and the sound emission port 9. Note that the division into two acoustic spaces is not limited to the case where the acoustic resistance member 51 completely divides into two spaces, and it is sufficient to obtain the same effect (or an effect similar thereto) as in the case of being acoustically completely divided into two spaces. For example, even when it can be regarded as being acoustically divided into two spaces by arranging the acoustic resistance member 51 in a part between the two acoustic spaces as shown in FIGS. 17 and 18 described later, the same effect can be obtained.

[0114] The block diagram of the internal configuration of the acoustic reproducing apparatus 1B has the same configuration as that in FIG. 3.

[0115] Since the acoustic reproducing apparatus 1B has the configuration shown in FIGS. 3 and 7, the first noise canceling signal Snc1 generated based on the high-frequency component of the first sound collecting signal S1, which is a signal collected in the stable front space 7a, is capable of improving the noise canceling performance while further suppressing the generation of howling.

[0116] Also, the second noise canceling signal Snc2 is a signal capable of bringing the canceling point closer to the eardrum.

[0117] Therefore, by synthesizing the first noise canceling signal Snc1 based on the high-frequency component of the first sound collecting signal S1 and the second noise canceling signal Snc2 based on the low-frequency component of the second sound collecting signal S2 to generate the synthesized noise canceling signal Snc, it is possible to further improve the noise canceling performance at the eardrum position while suppressing the generation of howling.

[0118] <3-2. Acoustic playback device as a headset> Fig. 8 shows a configuration example of an acoustic playback device 1C as a headset. Regarding the same configurations as the acoustic playback device 1 shown in Fig. 2, the acoustic playback device 1A shown in Fig. 6, and the acoustic playback device 1B shown in Fig. 7, the same reference numerals are used and the description is omitted as appropriate.

[0119] The acoustic playback device 1C includes a housing 3 in which an internal space 2 is formed, a driver unit 4 disposed in the internal space 2, and a first microphone 11 and a second microphone 12 used for noise canceling processing by a feedback method.

[0120] The driver unit 4 is capable of acoustic output by including a diaphragm 4a.

[0121] The housing 3 includes a base portion 42 in which a mounting recess 41 for mounting the driver unit 4 is formed, and an ear pad 43 attached to the peripheral edge in front of the mounting recess 41. The inner peripheral edge in front of the ear pad 43 is formed as a sound emitting port 9.

[0122] In front of the diaphragm 4a of the driver unit 4, a protective member 44 formed in a mesh shape, for example, is attached to protect the diaphragm 4a.

[0123] The internal space 2 consists of a front space 7a which is a space surrounded by the ear pad 43, the front surface of the driver unit 4, and the sound emitting port 9, and a rear space 7b which is a space surrounded by the base portion 42 and the rear surface of the driver unit 4.

[0124] The acoustic reproduction device 1C is provided with an acoustic resistance member 51 that further divides the front space 7a into two acoustic spaces. Specifically, the front space 7a is separated by the acoustic resistance member 51 into an inner space 52, which is the space on the side of the driver unit 4, and an outer space 53, which is the space on the side of the sound emission port 9. Note that the inner space 52 and the outer space 53 can also be regarded as the front space 7a and the sound guiding space 8 in the acoustic reproduction device 1 as an earphone.

[0125] The acoustic resistance member 51 is attached to, for example, the protective member 44.

[0126] The first microphone 11 is attached to the rear surface of the protective member 44 such that the sound collection surface 11a faces substantially the diaphragm 4a.

[0127] The second microphone 12 is attached to the front surface of the acoustic resistance member 51 such that the sound collection surface 12a faces the sound emission port 9.

[0128] That is, the first microphone 11 and the second microphone 12 included in the acoustic reproduction device 1C are arranged in different acoustic spaces separated by the acoustic resistance member 51.

[0129] The block diagram of the internal configuration of the acoustic reproduction device 1C has the same configuration as that of FIG. 3. That is, in the acoustic reproduction device 1C, a first noise canceling signal Snc1 is generated based on the high-frequency component of the first sound collection signal S1 of the first microphone 11.

[0130] Therefore, by generating a combined noise canceling signal Snc using the first sound collection signal S1 of the first microphone 11 arranged in the inner space 52, which is acoustically a stable space, it is possible to further suppress the occurrence of howling.

[0131] Also, by generating a combined noise canceling signal Snc using the low-frequency component of the second sound collection signal S2, it is possible to improve the noise canceling performance at the eardrum position.

[0132] <4. Third Embodiment> <4-1. Acoustic Reproduction Device as Earphone> The acoustic reproduction device 1D as an earphone in the third embodiment includes an acoustic resistance member 51 that divides the internal space 2 into a plurality of acoustic spaces, and the second microphone 12 is arranged behind the driver unit 4.

[0133] Specifically, it will be described with reference to FIG. 9. The acoustic reproduction device 1D includes a housing 3 in which the internal space 2 is formed, a driver unit 4 arranged in the internal space 2, a first microphone 11, and a second microphone 12.

[0134] The internal space 2 is composed of an arrangement space 7 in which each part is arranged and an acoustic conduction space 8 surrounded by the acoustic conduction tube 6. The arrangement space 7 is composed of a front space 7a that is the space in front of the driver unit 4 and a rear space 7b that is the space behind the driver unit 4.

[0135] The acoustic reproduction device 1D includes an acoustic resistance member 51 that separates both spaces between the front space 7a and the acoustic conduction space 8. That is, the front space 7a is made into an acoustically stable space by being the space surrounded by the box-shaped portion 5 of the housing 3, the driver unit 4, and the acoustic resistance member 51.

[0136] The first microphone 11 is arranged in the front space 7a such that the sound collection surface 11a substantially faces the diaphragm 4a. The second microphone 12 is arranged in the rear space 7b such that the sound collection surface 12a does not face the diaphragm 4a.

[0137] The block diagram of the internal configuration of the acoustic reproduction device 1D has the same configuration as that of FIG. 3.

[0138] In the second microphone 12 disposed in the rear space 7b, the sound pressure opposite to the sound pressure emitted forward from the diaphragm 4a and the noise entering through the housing 3 can be collected. Further, the signal collected by the second microphone 12 can be configured to be less affected by changes in the transfer function of the space from the driver unit to the microphone.

[0139] Therefore, by generating a synthesized noise cancellation signal Snc using the second collected sound signal S2 from the second microphone 12, the noise cancellation performance can be improved.

[0140] In this example, an example in which the first microphone 11 is disposed in the front space 7a and the second microphone 12 is disposed in the rear space 7b is shown. However, the first microphone 11 may be disposed in the rear space 7b and the second microphone 12 may be disposed in the sound guiding space 8.

[0141] <4-2. Acoustic playback device as a headphone> The acoustic playback device 1E as a headphone in the third embodiment will be described with reference to FIG. 10. Regarding the same configurations as the various acoustic playback devices described above, such as the acoustic playback device 1 shown in FIG. 2 and the acoustic playback device 1A shown in FIG. 6, the same reference numerals are given and the description will be omitted as appropriate.

[0142] The acoustic playback device 1E includes a housing 3 in which an internal space 2 is formed, a driver unit 4 disposed in the internal space 2, and a first microphone 11 and a second microphone 12 used for noise cancellation processing by a feedback method.

[0143] The driver unit 4 is capable of acoustic output by including a diaphragm 4a.

[0144] The housing 3 includes a base portion 42 and ear pads 43. The inner peripheral edge in front of the ear pads 43 is formed as a sound emission port 9.

[0145] A protective member 44 is attached in front of the diaphragm 4a of the driver unit 4.

[0146] The first microphone 11 is disposed in the front space 7a. Specifically, the first microphone 11 is attached to the rear surface of the protective member 44 such that the sound collecting surface 11a faces substantially the diaphragm 4a.

[0147] The second microphone 12 is disposed in the rear space 7b. Specifically, the second microphone 12 is attached to the housing 3 such that the sound collecting surface 12a faces in a direction different from that of the sound collecting surface 11a of the first microphone 11.

[0148] That is, the first microphone 11 and the second microphone 12 included in the acoustic playback device 1E are disposed in different acoustic spaces.

[0149] In the second microphone 12 disposed in the rear space 7b, a sound pressure having a phase opposite to that of the sound pressure emitted forward from the diaphragm 4a and noise that has entered through the housing 3 can be collected.

[0150] Therefore, by generating a combined noise canceling signal Snc using the second sound collecting signal S2 from the second microphone 12, it is possible to improve the noise canceling performance.

[0151] <5. The Fourth Embodiment> <5-1. Configuration of the Acoustic Playback Device> FIG. 11 shows an acoustic playback device 1F as an earphone in the fourth embodiment. The acoustic playback device 1F in the fourth embodiment includes a third microphone 61 for generating a feedforward type noise canceling signal.

[0152] Specifically, the configuration of the acoustic playback device 1F will be described with reference to FIG. 11.

[0153] The audio playback device 1F includes a housing 3 in which an internal space 2 is formed, a driver unit 4 disposed in the internal space 2, a first microphone 11 and a second microphone 12 used for noise cancellation processing by a feedback method, and a third microphone 61 used for noise cancellation processing by a feedforward method.

[0154] The internal space 2 is composed of an arrangement space 7 where each part is arranged and an acoustic conduction space 8 surrounded by an acoustic conduction pipe 6. The arrangement space 7 is composed of a front space 7a which is the space in front of the driver unit 4 and a rear space 7b which is the space behind the driver unit 4.

[0155] The first microphone 11 is arranged in the front space 7a such that the sound collection surface 11a faces substantially opposite to the diaphragm 4a. The second microphone 12 is arranged in the acoustic conduction space 8 such that the sound collection surface 12a faces a direction different from that of the sound collection surface 11a of the first microphone 11.

[0156] The third microphone 61 is attached to the housing 3 such that the sound collection surface 61a is located in the external space so as to be able to collect external sound of the audio playback device 1F.

[0157] Thereby, the noise cancellation processing by the feedback method and the noise cancellation processing by the feedforward method can be combined, and the noise cancellation performance can be improved.

[0158] The audio playback device 1F may be provided with an acoustic resistance member 51 that separates the two spaces between the front space 7a and the acoustic conduction space 8. Thereby, the front space 7a is made into an acoustically stable space surrounded by the box-shaped portion 5 of the housing 3, the driver unit 4, and the acoustic resistance member 51.

[0159] <5-2. Internal Configuration of Audio Playback Device> FIG. 12 is a block diagram of the internal configuration of the audio playback device 1F. The audio playback device 1F includes, as respective units for processing the first sound collection signal S1 of the first microphone 11, a first amplifier 21A, a first ADC 22A, and a first DSP 23A.

[0160] Also, the audio playback device 1F includes, as respective units for processing the sound collection signal S2 of the second microphone 12, a second amplifier 21B, a second ADC 22B, and a second DSP 23B.

[0161] Furthermore, the audio playback device 1 includes, as respective units for processing the sound collection signal S3 of the third microphone 61, a third amplifier 21C, a third ADC 22C, and a third DSP 23C.

[0162] The audio playback device 1F includes adders 24, 25, an equalizer circuit 26, a DAC 27, a power amplifier 28, and further includes an adder 62.

[0163] As described above, the first sound collection signal S1 is the result of collecting sound including noise in the front space 7a of the diaphragm 4a of the driver unit 4. The first sound collection signal S1 is amplified by the first amplifier 21A, then converted into a digital signal by the first ADC 22A, and input to the first DSP 23A.

[0164] The first DSP 23A includes a digital filter for generating a feedback-type noise cancellation signal (see FIG. 4). The signal generated by the first DSP 23A is input to the adder 24.

[0165] As described above, the second sound collection signal S2 is the result of collecting sound including noise in the sound guide space 8 which is the internal space of the sound guide tube 6. The second sound collection signal S2 is amplified by the second amplifier 21B, then converted into a digital signal by the second ADC 22B, and input to the second DSP 23B.

[0166] The second DSP 23B is provided with a digital filter for generating a feedback-type noise canceling signal (see FIG. 5). The signal generated by the second DSP 23B is input to the adder 24.

[0167] The adder 24 adds and synthesizes the first noise canceling signal Snc1 generated based on the first sound collection signal S1 of the first microphone 11 and the second noise canceling signal Snc2 generated based on the second sound collection signal S2 of the second microphone 12, and outputs the result to the adder 62.

[0168] The third sound collection signal S3 is obtained by collecting sound including noise in the external space of the acoustic playback device 1F. The third sound collection signal S3 is amplified by the third amplifier 21C, then converted into a digital signal by the third ADC 22C, and input to the third DSP 23C.

[0169] The third DSP 23C is provided with a digital filter for generating a feedforward-type noise canceling signal. Specifically, as shown in FIG. 13, it is provided with a third FF filter 63.

[0170] The third FF filter 63 is a digital filter for generating a feedforward-type digital noise canceling signal. That is, the third FF filter 63 generates a third noise canceling signal Snc3 based on the third sound collection signal S3. The third noise canceling signal Snc3 generated by the third DSP 23C is input to the adder 62.

[0171] The adder 62 adds and synthesizes the combined signal of the first noise cancellation signal Snc1 generated based on the first sound collection signal S1 of the first microphone 11 and the second noise cancellation signal Snc2 generated based on the second sound collection signal S2 of the second microphone 12, and the third noise cancellation signal Snc3 generated based on the third sound collection signal S3 of the third microphone 61, and outputs the combined noise cancellation signal Snc to the adder 25.

[0172] In addition to the combined noise cancellation signal Snc, a digital signal based on the sound source signal Sm is also input to the adder 25.

[0173] The sound source signal Sm is input to the equalizer circuit 26. The equalizer circuit 26 performs equalizing processing for sound quality correction processing and sound quality effect processing on the input sound source signal Sm, and outputs the obtained digital signal to the adder 25. The equalizer circuit 26 may be configured, for example, within a DSP.

[0174] The adder 25 adds and synthesizes the combined noise cancellation signal Snc and the signal from the equalizer circuit 26, and outputs the output acoustic signal to the DAC 27.

[0175] The output signal from the adder 25 is converted into an analog signal by the DAC 27, then amplified by the power amplifier 28 and supplied to the driver unit 4.

[0176] In the driver unit 4, acoustic output processing based on the input output acoustic signal is executed. As a result, the reproduced sound with reduced noise at a predetermined noise cancellation point is in a state where it can be listened to by the listener.

[0177] As shown in FIG. 11, since the first microphone 11 is arranged such that the sound collection surface 11a faces the diaphragm 4a of the driver unit 4, the first noise cancellation signal Snc1 can suppress the occurrence of howling.

[0178] Also, by using the second sound collection signal S2 from the second microphone 12 with the sound collection surface 12a being in a different direction from the first microphone 11, it is possible to bring the cancellation point closer to the eardrum.

[0179] Furthermore, since the sound collection surface 61a is configured to pick up noise in the external space of the sound playback device 1F, it is possible to perform noise cancellation processing by the feedforward method. By using the third sound collection signal S3 from the third microphone 61, the noise cancellation performance can be improved.

[0180] In FIG. 12, an example in which the first DSP 23A, the second DSP 23B, and the third DSP 23C are provided is shown, but digital filters for the first sound collection signal S1, the second sound collection signal S2, and the third sound collection signal S3 may be formed in one DSP. Also, in that case, an equalizer circuit 26 may be formed in the same DSP.

[0181] In FIG. 3, an example in which the sound source signal Sm is a digital signal is shown, but it may be an analog signal. In that case, the sound source signal Sm is converted into a digital signal using an ADC and input to the equalizer circuit 26.

[0182] Also, the sound playback device 1F as the fourth embodiment may be a sound playback device in the form of headphones equipped with the third microphone 61, and the same effects can be obtained even in that case.

[0183] <6. Modification Example> <6-1. First Modification Example> In each of the above-described examples, an example in which digital filters for generating noise cancellation signals are provided for the first sound collection signal S1 and the second sound collection signal S2 respectively has been described. That is, as described with reference to FIGS. 3, 4, and 5, in the acoustic playback device 1, a first FB filter 32 is provided as a digital filter for generating a first noise canceling signal Snc1 using the first sound collection signal S1, and a second FB filter 34 is provided as a digital filter for generating a second noise canceling signal Snc2 using the second sound collection signal S2.

[0184] In order to reduce the amount of computation for digital filter processing, only one digital filter for generating the combined noise canceling signal Snc may be provided.

[0185] Specifically, with reference to FIG. 14, the internal configuration of the acoustic playback device 1G in which only one digital filter for generating the combined noise canceling signal Snc is provided will be described.

[0186] The acoustic playback device 1G includes a first amplifier 21A and a first ADC 22A as units for processing the first sound collection signal S1 of the first microphone 11, and an HPF 71. That is, the acoustic playback device 1G does not include a first DSP for performing digital filter processing on the first sound collection signal S1.

[0187] The first sound collection signal S1 is amplified by the first amplifier 21A, then converted into a digital signal by the first ADC 22A, and further input to the adder 73 after the low-frequency components are removed by the HPF 71.

[0188] The acoustic playback device 1G includes a second amplifier 21B and a second ADC 22B as units for processing the second sound collection signal S2 of the second microphone 12, and an LPF 72. That is, the acoustic playback device 1G does not include a second DSP for performing digital filter processing on the second sound collection signal S2.

[0189] The second sound collection signal S2 is amplified by the second amplifier 21B, then converted into a digital signal by the second ADC 22B, and further input to the adder 73 after the high-frequency components are removed by the LPF 72.

[0190] The adder 73 outputs to the FB filter 74, which is a digital filter for adding and synthesizing the high-frequency component of the first sound collection signal S1 of the first microphone 11 and the low-frequency component of the second sound collection signal S2 of the second microphone 12 to generate a noise cancellation signal.

[0191] The FB filter 74 performs digital filter processing for generating a noise cancellation signal Snc' based on the added and synthesized sound collection signal. The generated noise cancellation signal Snc' can be regarded as the aforementioned synthesized noise cancellation signal Snc.

[0192] The adder 25 adds and synthesizes the noise cancellation signal Snc' and the signal from the equalizer circuit 26, and outputs it to the DAC 27 as an output acoustic signal.

[0193] The DAC 27 converts the input signal from the adder 25 into an analog signal and outputs it to the power amplifier 28. The power amplifier 28 amplifies the input signal and supplies it to the driver unit 4.

[0194] In the driver unit 4, acoustic output processing based on the input output acoustic signal is executed.

[0195] Note that the HPF 71 shown in FIG. 14 may be provided in front of rather than behind the first ADC 22A. That is, filter processing for the analog signal may be performed. Similarly, the LPF 72 may be provided in front of the second ADC 22B.

[0196] Note that the HPF 71 can be substituted with a high-shelving filter, a high-peak EQ filter, etc. Also, the LPF 72 can be substituted with a low-shelving filter, a low-peak EQ filter, etc.

[0197] Furthermore, a configuration may be adopted in which neither the HPF 71 nor the LPF 72 is provided, and only the FB filter 74 is provided.

[0198] <6-2.Second Modified Example> In the second embodiment, an example in which the acoustic resistance member 51 is provided in the acoustic playback devices 1B and 1C was described. Here, regarding the attachment mode of the acoustic resistance member 51, the headphone-type acoustic playback device 1C will be exemplified and described.

[0199] One example of the attachment of the acoustic resistance member 51 to the protection member 44 is shown in FIG. 15. The acoustic resistance member 51 (illustrated by diagonal hatching) may be attached over the entire front surface of the protection member 44. Thereby, the space in front of the acoustic resistance member 51 (for example, the outer space 53) and the space behind (for example, the inner space 52) can be acoustically separated. Therefore, the space behind can be made into a more stable space acoustically, and the generation of howling can be suppressed.

[0200] A second example of the attachment of the acoustic resistance member 51 to the protection member 44 is shown in FIG. 16. The acoustic resistance member 51 (illustrated by diagonal hatching) may be attached from the front so as to cover substantially the central portion of the protection member 44. In this case, it is preferable that the first microphone 11 is positioned at the center of the acoustic resistance member 51.

[0201] A third example of the attachment of the acoustic resistance member 51 to the protection member 44 is shown in FIG. 17. The acoustic resistance member 51 (illustrated by diagonal hatching) may be attached from the front so as to cover the upper half region, the lower half region, the right half region, or the left half region of the protection member 44. Also, in that case, it is preferable that the acoustic resistance member 51 is positioned so as to be offset with respect to the central portion of the protection member 44 to the portion covered by the acoustic resistance member 51.

[0202] Fig. 18 shows a fourth example of the attachment of the acoustic resistance member 51 to the protective member 44. The acoustic resistance member 51 (illustrated with diagonal hatching) may be attached from the front so as to cover the central portion from the upper end to the lower end of the protective member 44. Also, in that case, it is preferable that the first microphone 11 is positioned at the center of the acoustic resistance member 51.

[0203] In addition to the configuration in which the acoustic resistance member 51 is attached over the entire surface of the protective member 44 as shown in Fig. 15, even in the configurations shown in Figs. 16, 17, and 18, since the rear space can be made an acoustically stable space, the effect of suppressing the generation of howling can be obtained.

[0204] <6-3. Others> In each of the above examples, headphones or earphones are cited as examples of the acoustic playback device, but other examples are also conceivable. For example, the above-described configuration can also be applied to the noise cancellation signal generated for performing noise cancellation processing in a space having a certain extent such as a room. That is, the first MC and the second MC used for FB control are provided inside the room. In this case, the second MC is arranged closer to the window or the door than the first MC. Furthermore, a third MC used for FF control may be provided outside the room. In this way, when watching music or the like in a room as an acoustic space, noise can be reduced and a space suitable for viewing can be provided.

[0205] <7. Summary> In the above-described acoustic playback devices 1 (1A, 1B, 1C, 1D, 1E, 1G) such as headphones and earphones, a first microphone 11 used for noise cancellation processing by a feedback method, and a second microphone 12 having a sound collection surface in a direction different from that of the first microphone 11 and used for noise cancellation processing by a feedback method, and an acoustic signal processing unit (first DSP 23A, second DSP 23B, etc.) that generates a noise canceling signal using a first sound collection signal S1 collected by the first microphone 11 and a second sound collection signal S2 collected by the second microphone 12. In a configuration including a plurality of microphones for use in noise cancellation processing by a feedback method, it is easy to collect sound in a plurality of acoustic spaces (for example, the front space 7a of the driver unit 4 and the space in the sound guide tube (sound guide space 8)) in the acoustic playback device 1. By using a plurality of microphones used in the feedback method, it is possible to contribute to an improvement in the noise cancellation effect. However, by changing the sound collection direction of each microphone, it is possible to appropriately collect an acoustic signal including noise in a plurality of spaces, which is suitable for improving the noise cancellation effect by the feedback method.

[0206] As described in the first embodiment (FIG. 2), in the acoustic playback device 1, the sound collection surface 11a of the first microphone 11 may be located closer to the driver unit 4 that performs acoustic output based on the noise canceling signal than the sound collection surface 12a of the second microphone 12. Thereby, the transfer function of the space from the driver unit 4 to the sound collection surface 11a of the first microphone 11 is made less likely to change. Therefore, it is possible to generate a first noise canceling signal Snc1 having sufficient noise canceling performance with the filter coefficients set in the first FB filter 32. That is, by adding the first noise canceling signal Snc1 generated from the sound collection signal of the first microphone 11, the noise canceling performance can be improved.

[0207] As described in the first embodiment (FIG. 2), in the acoustic playback device 1, the sound collecting surface 11a of the first microphone 11 may be positioned to face the sound emitting direction (front) of the driver unit 4 that performs acoustic output based on the noise canceling signal. Thereby, the transfer function of the space from the driver unit 4 to the sound collecting surface 11a of the first microphone 11 is made less likely to change. Therefore, it becomes possible to generate the first noise canceling signal Snc1 having sufficient noise canceling performance with the filter coefficient set in the first FB filter 32. That is, by adding the first noise canceling signal Snc1 generated by the sound collecting signal of the first microphone 11, the noise canceling performance can be improved.

[0208] As described in the first embodiment (FIG. 2), in the acoustic playback device 1, a housing 3 having a sound emitting port 9 where the driver unit 4 that performs acoustic output based on the noise canceling signal is disposed and the output sound from the driver unit 4 is emitted is provided, and the first microphone 11 and the second microphone 12 are disposed inside the housing 3, and the second microphone 12 may be positioned closer to the sound emitting port 9 than the first microphone 11. Thereby, the second microphone 12 can collect sound at a position closer to the eardrum than the first microphone 11. Therefore, the cancellation point becomes closer to the eardrum, and the noise canceling performance can be improved.

[0209] As described in the first embodiment (FIGS. 2 and 6), the second embodiment (FIGS. 7 and 8), the third embodiment (FIGS. 9 and 10), the fourth embodiment (FIG. 11), etc., in the acoustic playback device 1, the sound collecting surface 12a of the second microphone 12 may be positioned so as not to face the sound emitting direction (front) of the driver unit 4 that performs acoustic output based on the noise canceling signal. Thereby, the second microphone 12 is made more likely to collect noise. Therefore, the noise cancellation performance can be improved.

[0210] As described in the first embodiment (FIG. 6), in the acoustic playback device 1, at least one acoustic space is located in the housing 3 in the sound emission direction of the driver unit 4, and the first microphone 11 and the second microphone 12 may be located in one acoustic space. Thereby, the noise components in the acoustic space where the microphone is arranged can be collected with high precision. Therefore, the filter coefficient can be set more appropriately, and the noise cancellation performance can be improved. In addition, the arrangement of members for dividing the acoustic space into a plurality of parts is not required. Thereby, the cost related to manufacturing can be reduced. Further, by reducing the number of parts, the assembly man-hours can be reduced.

[0211] As described in the first embodiment (FIG. 6), the second embodiment (FIG. 8), the third embodiment (FIG. 10), etc., in the acoustic playback device 1, the first microphone 11 is positioned such that the sound collection surface 11a faces the sound emission direction of the driver unit 4, and the second microphone 12 may be positioned such that the sound collection surface 12a faces the same direction as the sound emission direction of the driver unit 4. Thereby, the transfer function of the space from the driver unit 4 to the sound collection surface 11a of the first microphone 11 is less likely to change. Also, the second microphone 12 is made more likely to collect noise at a position closer to the eardrum. Therefore, by generating a noise cancellation signal using both the first sound collection signal S1 of the first microphone 11 and the second sound collection signal S2 of the second microphone 12, it is possible to improve the noise cancellation performance while suppressing the occurrence of howling.

[0212] As described in the first embodiment (Fig. 2), the second embodiment (Figs. 7 and 8), or the third embodiment (Figs. 9 and 10), etc., in the acoustic playback device 1, the first microphone 11 and the second microphone 12 may be arranged in different acoustic spaces. As a result, the noises collected by the first microphone 11 and the second microphone 12 are made different. Therefore, by generating a noise cancellation signal based on both the first collected sound signal S1 of the first microphone 11 and the second collected sound signal S2 of the second microphone 12, it is possible to improve the noise cancellation performance.

[0213] As described in the first embodiment (Fig. 2), the second embodiment (Figs. 7 and 8), or the third embodiment (Figs. 9 and 10), etc., in the acoustic playback device 1, a plurality of acoustic spaces are provided in the housing 3, and the first microphone 11 and the second microphone 12 may be located in different spaces among the plurality of acoustic spaces. As a result, both the first microphone 11 and the second microphone 12 are arranged within the housing 3. Also, the noises collected by the first microphone 11 and the second microphone 12 are made more different. Therefore, it is possible to obtain the collected sound signals at different positions within the housing, and it is possible to improve the noise cancellation performance.

[0214] As described in the second embodiment (Figs. 7 and 8), etc., in the acoustic playback device 1, an acoustic resistance member 51 that separates the first acoustic space (front space 7a, inner space 52) where the first microphone 11 is located and the second acoustic space (sound guiding space 8) where the second microphone 12 is located may be arranged. As a result, it is possible to make the space from the driver unit 4 to the microphone (first microphone 11) in one acoustic space (front space 7a) a stable space where the transfer function hardly changes. Therefore, a high noise cancellation effect can be obtained using the set filter coefficients.

[0215] As described in the second embodiment (Figs. 7 and 8) and the like, in the acoustic reproduction device 1, a driver unit 4 that performs acoustic output based on a noise canceling signal is disposed, and a housing 3 having a sound emission port 9 from which the output sound from the driver unit 4 is emitted is provided. The first acoustic space (front space 7a) may be a space surrounded by the driver unit 4, the acoustic resistance member 51, and the housing 3, and the second acoustic space (sound guiding space 8) may be a space surrounded by the acoustic resistance member 51, the housing 3, and the sound emission port 9. Thereby, the first acoustic space is a stable space in which the transfer function of the space hardly changes. Also, the second acoustic space is a space in which it is easy to collect noise at a position closer to the eardrum. By generating the first noise canceling signal Snc1 using the first sound collection signal S1 of the first microphone 11 disposed in the first acoustic space (the front space 7a in Fig. 2, the inner space 52 in Fig. 8, etc.) that is an acoustically stable space, the filter coefficient set in the first FB filter 32 can be made appropriate with high noise canceling performance. Also, an acoustic reproduction device such as an earphone or a headphone may be deformed depending on the usage state. In that case, due to a change in the space transfer function, the set filter coefficient may become inappropriate, leading to the occurrence of howling or the like. Even in such a case, since the first acoustic space is shielded from the outside by the acoustic resistance member 51 and the acoustic stable state is maintained, an appropriate setting of the filter coefficient can be ensured, and the occurrence of howling can be suppressed. However, in the microphone (the first microphone 11) disposed in the stable space, there may be a case where noise near the point where the noise canceling effect is desired to be exhibited (i.e., near the eardrum) cannot be sufficiently collected. When the noise collection is insufficient, the generated noise canceling signal may become inappropriate, and the active noise canceling effect at the eardrum position may be reduced. According to this configuration, since the second noise canceling signal Snc2 is generated using the second collected sound signal S2 of the second microphone 12 arranged in the second acoustic space (such as the sound guiding space 8 in FIG. 2 or the external space 53 in FIG. 8) different from the first acoustic space, high noise canceling performance can be exhibited while suppressing howling.

[0216] As described in the third embodiment (FIGS. 9 and 10) and the like, in the acoustic playback device 1, the first microphone 11 is positioned on the front side in the sound emission direction of the driver unit 4 that performs acoustic output based on the noise canceling signal, and the second microphone 12 may be positioned on the rear side of the driver unit 4. Thereby, for example, the second microphone 12 positioned behind the driver unit 4 can collect the sound of the opposite phase of the acoustic output. Further, the transfer function of the space from the driver unit 4 to the sound collection surface 12a of the second microphone 12 is made less likely to change depending on the wearing state of the listener. At this time, the second microphone 12 also collects the noise that could not be completely canceled by the noise canceling signal generated based on the first collected sound signal S1 of the first microphone 11. Therefore, by generating the noise canceling signal based on not only the first collected sound signal S1 of the first microphone 11 but also the second collected sound signal S2 of the second microphone 12, high noise canceling performance can be exhibited.

[0217] As described in the first embodiment (FIGS. 4 and 5), in the acoustic playback device 1, a first feedback filter (first FB filter 32) that generates the first noise canceling signal Snc1 based on the high frequency component of the first collected sound signal S1, and a second feedback filter (second FB filter 34) that generates the second noise canceling signal Snc2 based on the low frequency component of the second collected sound signal S2 are provided, and the acoustic signal processing unit may generate the noise canceling signal based on the first noise canceling signal Snc1 and the second noise canceling signal Snc2. Since the first microphone 11 is disposed closer to the driver unit 4 than the second microphone 12, the filter coefficient set for the first FB filter 32 is less likely to be inappropriate than the filter coefficient set for the second FB filter 34. Accordingly, it is possible to make the first noise canceling signal Snc1 based on the first sound collection signal S1 less likely to generate howling than the second noise canceling signal Snc2 based on the second sound collection signal S2. Therefore, for high-frequency components that are likely to cause howling, a first noise canceling signal Snc1 that is less likely to generate howling is generated using the first sound collection signal S1, and for low-frequency components that are less likely to cause howling, a second noise canceling signal Snc2 with improved noise canceling performance is generated using the second sound collection signal S2. By generating a noise canceling signal using these, it is possible to improve the noise canceling performance while suppressing the occurrence of howling.

[0218] As described in the first embodiment (FIGS. 4 and 5), in the acoustic playback device 1, the high-frequency component of the first sound collection signal S1 may be extracted by the high-pass filter HPF31, the high-shelving filter, or the high-peak EQ filter, and the low-frequency component of the second sound collection signal S2 may be extracted by the low-pass filter LPF33, the low-shelving filter, or the low-peak EQ filter. Thereby, it is possible to input a sound collection signal of a high-frequency component that is likely to howl to the feedback loop of the first microphone 11 in which the transfer function of the space from the driver unit 4 to the microphone is less likely to change. Also, it is possible to input a sound collection signal of a low-frequency component to the feedback loop of the second microphone 12 that is likely to collect noise at a position closer to the eardrum. Therefore, the occurrence of howling can be suppressed. Also, by removing the low-frequency component of the first sound collection signal S1, the noise canceling performance based on the second sound collection signal S2 can be improved.

[0219] As described in the fourth embodiment (FIG. 11) and the like, the audio playback device 1 includes a third microphone 61 used for noise cancellation processing by the feedforward method, and the audio signal processing unit (the first DSP 23A, the second DSP 23B, the third FF filter 63, etc.) may generate a noise cancellation signal using the first collected sound signal S1, the second collected sound signal S2, and the third collected sound signal S3 collected by the third microphone 61. For example, it is conceivable to provide the third microphone 61 so as to collect the external sound of the audio playback device 1F. By using the third collected sound signal S3 by such a third microphone 61, the noise cancellation performance can be improved.

[0220] As in the various embodiments described above, the signal processing device includes an audio signal processing unit (the first DSP 23A, the second DSP 23B, etc.) that generates a noise cancellation signal using the first collected sound signal S1 collected by the first microphone 11 used for noise cancellation processing by the feedback method and the second collected sound signal S2 collected by the second microphone 12 that has a sound collection surface in a direction different from that of the first microphone 11 and is used for noise cancellation processing by the feedback method.

[0221] The signal processing method executed by the signal processing device is a method that generates a noise cancellation signal using the first collected sound signal S1 collected by the first microphone 11 used for noise cancellation processing by the feedback method and the second collected sound signal S2 collected by the second microphone 12 that has a sound collection surface in a direction different from that of the first microphone 11 and is used for noise cancellation processing by the feedback method. With such a signal processing apparatus and signal processing method, it is easy to collect sound in a plurality of acoustic spaces (for example, the front space 7a of the driver unit 4 and the space in the sound guide tube (sound guide space 8)) in the acoustic playback apparatus 1. By using a plurality of microphones used in the feedback method, it is possible to contribute to the improvement of the noise cancellation effect. However, by changing the sound collection direction of each microphone, it is possible to appropriately collect an acoustic signal including noise in a plurality of spaces. As a result, it is possible to improve the noise cancellation effect by the feedback method.

[0222] Note that the effects described in this specification are merely examples and are not limiting, and there may be other effects. In addition, each of the above-described examples can be combined in any manner as long as the combination is not impossible.

[0223] <8. The present technology> Note that the headphone apparatus of the present technology can also adopt the following configuration. (1) A first microphone used for noise cancellation processing by a feedback method, A second microphone having a sound collection surface in a direction different from that of the first microphone and used for noise cancellation processing by a feedback method, An acoustic signal processing unit that generates a noise canceling signal using a first sound collection signal collected by the first microphone and a second sound collection signal collected by the second microphone. An acoustic playback apparatus. (2) The sound collection surface of the first microphone is located closer to a driver unit that performs acoustic output based on the noise canceling signal than the sound collection surface of the second microphone. The acoustic playback apparatus according to (1) above. (3) The sound collection surface of the first microphone is positioned to face the sound emission direction of a driver unit that performs acoustic output based on the noise cancellation signal. The acoustic playback device according to any one of (1) to (2) above. (4) It includes a housing in which a driver unit that performs acoustic output based on the noise cancellation signal is arranged and that has a sound emission port from which the output sound from the driver unit is emitted. The first microphone and the second microphone are arranged inside the housing. The second microphone is positioned closer to the sound emission port than the first microphone. The acoustic playback device according to any one of (1) to (3) above. (5) The sound collection surface of the second microphone is positioned so as not to face the sound emission direction of a driver unit that performs acoustic output based on the noise cancellation signal. The acoustic playback device according to any one of (1) to (4) above. (6) At least one acoustic space is positioned inside the housing in the sound emission direction of the driver unit. The first microphone and the second microphone are positioned in the one acoustic space. The acoustic playback device according to (4) above. (7) The first microphone is positioned such that the sound collection surface faces the sound emission direction of the driver unit. The second microphone is positioned such that the sound collection surface has the same direction as the sound emission direction of the driver unit. The acoustic playback device according to (6) above. (8) The first microphone and the second microphone are arranged in different acoustic spaces. The acoustic playback device according to any one of (1) to (5) above. (9) A plurality of acoustic spaces are provided inside the housing. The first microphone and the second microphone are located in different spaces in the plurality of acoustic spaces. The acoustic playback device according to any one of (4) or (6) above. (10) An acoustic resistance member that separates the first acoustic space where the first microphone is located from the second acoustic space where the second microphone is located is arranged. The acoustic playback device according to (8) above. (11) A housing is provided with a driver unit that performs acoustic output based on the noise cancellation signal and has a sound emission port through which the output sound from the driver unit is emitted. The first acoustic space is a space surrounded by the driver unit, the acoustic resistance member, and the housing. The second acoustic space is a space surrounded by the acoustic resistance member, the housing, and the sound emission port. The acoustic playback device according to (10) above. (12) The first microphone is located on the front side in the sound emission direction of the driver unit that performs acoustic output based on the noise cancellation signal. The second microphone is located on the rear side of the driver unit. The acoustic playback device according to any one of (1) to (11) above. (13) A first feedback filter that generates a first noise cancellation signal based on the high-frequency component of the first sound collection signal, A second feedback filter that generates a second noise cancellation signal based on the low-frequency component of the second sound collection signal, and The acoustic signal processing unit generates the noise cancellation signal based on the first noise cancellation signal and the second noise cancellation signal. The acoustic playback device according to (2) above. (14) The high-frequency component of the first sound-collecting signal is extracted by a high-pass filter, a high-shelving filter, or a high-peak EQ filter, The low-frequency component of the second sound-collecting signal is extracted by a low-pass filter, a low-shelving filter, or a low-peak EQ filter The acoustic playback device according to (13) above. (15) Comprising a third microphone used for noise cancellation processing by a feedforward method, The acoustic signal processing unit generates the noise cancellation signal using the first sound-collecting signal, the second sound-collecting signal, and a third sound-collecting signal collected by the third microphone. The acoustic playback device according to any one of (1) to (14) above. (16) Comprising an acoustic signal processing unit that generates a noise cancellation signal using a first sound-collecting signal collected by a first microphone used for noise cancellation processing by a feedback method and a second sound-collecting signal collected by a second microphone having a sound collection surface in a direction different from that of the first microphone and used for noise cancellation processing by a feedback method. Signal processing device. (17) Generating a noise cancellation signal using a first sound-collecting signal collected by a first microphone used for noise cancellation processing by a feedback method and a second sound-collecting signal collected by a second microphone having a sound collection surface in a direction different from that of the first microphone and used for noise cancellation processing by a feedback method. Signal processing method.

Description of Signs

[0224] 1, 1A, 1B, 1C, 1D, 1E, 1F Acoustic playback device 3 Housing 4 Driver unit 7a Front space (first acoustic space) 8 Sound conduction space (second acoustic space) 9 Sound output port 11 First microphone 11a Sound collection surface 12 Second microphone 12a Sound collection surface 23A First DSP (acoustic signal processing unit) 23B Second DSP (acoustic signal processing unit) 31 HPF 32 First FB filter 33 LPF 34 Second FB filter 51 Acoustic resistance member 52 Inner space (first acoustic space) 61 Third microphone 63 Third FF filter 71 HPF 72 LPF S1 First sound collection signal S2 Second sound collection signal S3 Third sound collection signal Snc1 First noise cancellation signal Snc2 Second noise cancellation signal Snc Composite noise cancellation signal

Claims

A housing in which a driver unit that performs acoustic output based on a noise cancellation signal is disposed and that has a sound emission port from which output sound from the driver unit is emitted, an acoustic resistance member that separates a first acoustic space and a second acoustic space, a first microphone disposed in the first acoustic space and used for noise cancellation processing by a feedback method, a second microphone disposed in the second acoustic space, having a sound collection surface in a direction different from that of the first microphone, and used for noise cancellation processing by a feedback method, an acoustic signal processing unit that generates the noise cancellation signal using a first sound collection signal collected by the first microphone and a second sound collection signal collected by the second microphone, and the first acoustic space is a space surrounded by the driver unit, the acoustic resistance member, and the housing, the second acoustic space is a space surrounded by the acoustic resistance member, the housing, and the sound emission port an acoustic playback device.

2. The sound collection surface of the first microphone is positioned closer to the driver unit than the sound collection surface of the second microphone. The acoustic playback device according to claim 1.

3. The sound collection surface of the first microphone is positioned to face the sound emission direction of the driver unit. The acoustic playback device according to claim 1.

4. The second microphone is positioned closer to the sound emission port than the first microphone. The acoustic playback device according to claim 1.

5. The sound collection surface of the second microphone is positioned so as not to face the sound emission direction of the driver unit. The acoustic playback device according to claim 1.

6. a first feedback filter that generates a first noise cancellation signal based on a high-frequency component of the first sound collection signal, a second feedback filter that generates a second noise cancellation signal based on a low-frequency component of the second sound collection signal, and the acoustic signal processing unit generates the noise cancellation signal based on the first noise cancellation signal and the second noise cancellation signal. The acoustic playback device according to claim 2.

7. The high-frequency component of the first sound collection signal is extracted by a high-pass filter, a high-shelving filter, or a high-peak EQ filter. The low-frequency component of the second sound collection signal is extracted by a low-pass filter, a shelving filter, or a low-peak EQ filter. The acoustic playback device according to claim 6.

8. Comprising a third microphone used for noise cancellation processing by a feed-forward method, The acoustic signal processing unit generates the noise cancellation signal using the first sound collection signal, the second sound collection signal, and a third sound collection signal collected by the third microphone. The acoustic playback device according to claim 1.

9. A driver unit that performs acoustic output based on a noise cancellation signal is arranged, and a first sound collection signal collected by a first microphone arranged in a first acoustic space surrounded by the driver unit, an acoustic resistance member, and the housing and used for noise cancellation processing by a feedback method, and a second sound collection signal collected by a second microphone arranged in a second acoustic space surrounded by the acoustic resistance member, the housing, and the sound emission port and having a sound collection surface in a direction different from that of the first microphone and used for noise cancellation processing by a feedback method are used to generate the noise cancellation signal. An acoustic signal processing unit is provided. Signal processing device.

10. A driver unit that performs acoustic output based on a noise cancellation signal is arranged, and a first sound collection signal collected by a first microphone arranged in a first acoustic space surrounded by the driver unit, an acoustic resistance member, and the housing and used for noise cancellation processing by a feedback method, and a second sound collection signal collected by a second microphone arranged in a second acoustic space surrounded by the acoustic resistance member, the housing, and the sound emission port and having a sound collection surface in a direction different from that of the first microphone and used for noise cancellation processing by a feedback method are used to generate the noise cancellation signal. Signal processing method.

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