JP2019205124A - headphone - Google Patents

Abstract

To provide a headphone for enabling a wearer to hear sound from an outside while reducing noise.SOLUTION: A headphone includes: speakers 31; housings 32 for housing the speakers 31 and covering ears; error microphones 33 arranged at a side of each ear 11 with respect to housings 32; and control units 50. The housing 32 has communication holes 40 for allowing an internal space of the housing 32 to communicate with an external space of the housing 32. The control unit 50 can reduce noise in the neighborhood of the error microphone 33 by generating sound from the speaker 31 on the basis of an input signal from the error microphone 33. Since the housing 32 has communication holes 40, external sound can be transmitted to an inside of the housing 32. Thus, a wearer of the headphone 20 can hear external sound other than a frequency to be an active noise cancel object in a wearing state of the headphone 20.SELECTED DRAWING: Figure 2

Description

  The technology disclosed in this specification relates to headphones.

  Conventionally, headphones described in Patent Document 1 below are known as headphones capable of reducing noise. In Patent Document 1, a headphone includes a microphone and a speaker unit, generates a cancel signal based on noise detected by the microphone, and generates noise based on the cancel signal from the speaker unit, thereby reducing noise. Has been described.

JP 2010-109799 A

  In the above configuration, external sounds other than noise (for example, conversation sounds and alarm sounds) are blocked by headphones, so it is difficult for headphones users to hear external sounds. There was room.

  The present invention has been completed based on the above-described circumstances, and an object thereof is to provide a headphone capable of listening to sound from the outside while reducing noise.

  As means for solving the above problems, the technology disclosed in this specification includes a speaker, a housing that houses the speaker and covers an ear, and an ear that is disposed on the ear side with respect to the housing. A control unit that controls driving of the speaker, and the housing includes a communication hole that communicates an internal space of the housing with an external space of the housing, and the control The unit is characterized in that the noise near the ear-side microphone can be reduced by generating sound from the speaker based on an input signal from the ear-side microphone.

  Noise can be reduced by sound from the speaker. And since the housing | casing has a communicating hole, the sound from the exterior of a housing | casing can be transmitted to the inside of a housing | casing through a communicating hole. For this reason, the wearer of headphones can hear external sounds other than noise (sounds of frequencies targeted for active noise cancellation) with the headphones worn.

  The noise detected by the outer microphone, which is a reference microphone, includes an outer microphone arranged outside the casing, and a wall portion interposed between the outer microphone and the speaker. The sound can be generated from the speaker so that the input signal from the ear microphone that is an error microphone is minimized. Feedforward control using an external microphone located farther from the ear than the ear microphone as a reference microphone performs control with reference to noise at a position closer to the noise source than the ear microphone, so the referenced noise is Time to reach the ear can be earned, and responsiveness is assumed to be higher. Since high-frequency sound has a large phase change with time, higher responsiveness is required to reduce such sound. For this reason, the noise of a higher frequency can be reduced by performing feedforward control. In the above configuration, it is assumed that sound from the speaker leaks outside the housing through the communication hole of the housing. However, since a wall portion is interposed between the outer microphone and the speaker, it is possible to suppress a situation in which sound from the speaker reaches the outer microphone. As a result, the outer microphone can detect noise with less influence of sound from the speaker, and can reduce noise more reliably.

  The housing includes a bottom wall portion that has the communication hole and covers the speaker from the side opposite to the ear, and a peripheral wall portion that rises from the outer peripheral end of the bottom wall portion toward the ear side, The outer microphone may be disposed so as to overlap the bottom wall portion from the side opposite to the ear, and the wall portion may be interposed between the outer microphone and the bottom wall portion. Compared to the case where the outer microphone is provided on the peripheral wall portion, it becomes easier to detect sound over the entire circumference in the circumferential direction of the housing.

  According to the technology disclosed in this specification, it is possible to provide a headphone that can hear sound from the outside while reducing noise.

FIG. 3 is a schematic diagram showing the interior of the vehicle according to the first embodiment. Sectional drawing which shows the headphone main body of the headphone of FIG. Front view showing the headphones Headphone block diagram Block diagram showing a modification of the control unit Sectional drawing which shows the headphones main body which concerns on Embodiment 2. FIG. Block diagram of a headphone main body according to Embodiment 3

<Embodiment 1>
A first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, in this embodiment, a vehicle headphone 20 that can be used in a vehicle 10 is illustrated. The headphone 20 includes a pair of left and right headphone bodies 30 (only one headphone body is shown in FIG. 1), and a headband 21 that connects the headphone bodies. As shown in FIG. 2, the headphone main body 30 is a part that is attached to the occupant's ear 11. As shown in FIG. 2, the speaker 31, the housing 32 that houses the speaker 31 and covers the ear, and the ear 11 with respect to the housing 32. An error microphone 33 (ear-side microphone disposed on the ear side with respect to the housing), an ear pad 35, a control unit 50 that controls driving of the speaker 31, and an outer housing 32 are disposed. A reference microphone 36 (outside microphone), and a wall portion 37 interposed between the reference microphone 36 and the speaker 31.

  The casing 32 includes a bottom wall portion 38 that covers the speaker 31 from the side opposite to the ear 11 (left side in FIG. 2), and a peripheral wall portion 39 that rises from the outer peripheral end of the bottom wall portion 38 toward the ear 11 side (right side in FIG. 2). And has a substantially cylindrical shape as a whole. The speaker 31 (speaker unit) is fixed to the bottom wall portion 38, for example. The bottom wall portion 38 has a plurality of communication holes 40 that allow the internal space of the housing 32 to communicate with the external space of the housing 32. In addition, although the bottom wall part 38 which has the some communication hole 40 is formed by giving a punching process with respect to a metal thin plate, for example, it is not limited to this. The ear pad 35 is configured by covering a cushion member such as sponge with a covering member such as synthetic leather. The ear pad 35 has an annular shape, and is attached to the distal end portion (ear end portion) of the peripheral wall portion 39. The ear pad 35 is configured to come into contact with the periphery of the wearer's ear 11 at the end on the ear 11 side.

  The reference microphone 36 is arranged so as to overlap the bottom wall portion 38 from the side opposite to the ear 11. As shown in FIG. 3, the bottom wall portion 38 has, for example, a circular shape, and the reference microphone 36 is disposed so as to overlap the center of the bottom wall portion 38. That is, the reference microphone 36 is disposed at a location that coincides with the central axis L <b> 1 of the housing 32. In the present embodiment, the reference microphone 36, the speaker 31, and the error microphone 33 are arranged along the central axis L <b> 1 of the housing 32. Further, the reference microphone 36, the speaker 31, and the error microphone 33 are arranged in this order from the side far from the ear 11. The reference microphone 36 is held with respect to the housing 32 via a holding member 41 and a wall portion 37.

  The holding member 41 has a plate shape and includes three extending portions 43 extending radially from the reference microphone 36 as shown in FIG. As shown in FIG. 2, the extended end portion of each extended portion 43 is connected to the peripheral end portion of the bottom wall portion 38. The central portion of the holding member 41 is disposed with a space from the central portion of the bottom wall portion 38. As a result, the vibration of the speaker 31 is difficult to be transmitted to the reference microphone 36. A plurality of communication holes 42 are formed in the holding member 41 in the same manner as the bottom wall portion 38. The wall portion 37 has, for example, a substantially conical shape that tapers toward the ear 11 side, and covers the reference microphone 36 from the speaker 31 side. That is, the wall portion 37 is interposed between the reference microphone 36 and the bottom wall portion 38.

  Next, the configuration of the control unit 50 will be described. The control unit 50 is electrically connected to the error microphone 33, the reference microphone 36, and the speaker 31. The control unit 50 constitutes a feedforward active noise canceling device together with the error microphone 33, the reference microphone 36, and the speaker 31. The control unit 50 is mainly configured by, for example, a DSP (Digital Signal Processor). The control unit 50 can reduce noise near the error microphone 33 (inside the casing 32) by generating sound from the speaker 31 based on input signals from the reference microphone 36 and the error microphone 33. It has become. Specifically, the control unit 50 generates sound (pseudo noise) from the speaker 31 based on the noise detected by the reference microphone 36 so that the input signal (error signal) from the error microphone 33 is minimized. . For example, the control unit 50 may be built in the housing 32 or may be provided outside the housing 32.

  As shown in FIG. 4, the control unit 50 includes a secondary path model 51, a noise control filter 53 that generates a pseudo noise signal (pseudo noise signal), and a noise control filter 53 that minimizes the error signal. A coefficient updating unit 52 that updates the filter coefficient. The secondary path model 51 is a digital filter that simulates the acoustic transmission characteristics of the secondary path (sound transmission path from the speaker 31 to the error microphone 33). This is for performing the coefficient update process after removing.

  When noise is collected by the reference microphone 36 and input as the reference signal r (n), the reference signal r (n) is input to the secondary path model 51 and the noise control filter 53. In the secondary path model 51, the reference signal r (n) is filtered to generate a filtered reference signal x (n), which is output to the coefficient update unit 52. Based on the filtered reference signal x (n) and the error signal e (n), the coefficient update unit 52 updates the coefficient used by the noise control filter 53 so that the error signal e (n) is minimized. In the coefficient update unit 52, for example, the coefficient is updated using an LMS (least mean square) algorithm.

  The noise control filter 53 generates a pseudo noise signal u (n) by filtering the reference signal r (n) using the coefficient updated by the coefficient updating unit 52, and the pseudo noise signal u (n). Is output to the speaker 31. Thereby, the pseudo noise based on the pseudo noise signal u (n) is output from the speaker 31. This pseudo noise becomes a sound having an opposite phase to the noise near the error microphone 33 after passing through the secondary path. The error microphone 33 detects a sound in which the noise and the pseudo noise overlap (corresponding to a sound that cannot be canceled out by the pseudo noise) and inputs it as an error signal e (n). The error signal e (n) is a coefficient update unit. 52 is input. By repeating the above processing, the optimum pseudo noise is generated from the speaker 31 and the noise is canceled. As the noise control filter 53, for example, an FIR filter can be used.

  Next, the effect of this embodiment will be described. In the present embodiment, noise can be reduced by the sound from the speaker 31. And since the housing | casing 32 has the communicating hole 40, the sound from the exterior of the housing | casing 32 can be transmitted to the inside of the housing | casing 32 through the communicating hole 40. FIG. For this reason, the wearer of the headphones 20 can hear external sounds other than noise (sounds of frequencies targeted for active noise cancellation) with the headphones 20 worn.

  In the feedforward type active noise cancellation device (active noise suppression device) exemplified in the present embodiment, it is expected that noise of at least 500 Hz or less can be reduced. For this reason, the road noise (500 Hz or less) at the time of vehicle travel can be reduced. In addition, the consonant component of the voice is generally 1000 Hz or more, the ambulance siren is 960 Hz and 770 Hz, and the alarm sound of the level crossing is 523 Hz and 659 Hz. You can listen in the state. The frequency of noise that can be reduced by the headphones 20 is not limited to 500 Hz or less, and is set according to the configuration and control method of the headphones 20.

  As shown in the modification of FIG. 5, the control unit 50 limits the frequency band of the reference signal r (n), and the band limiting filter 62 limits the frequency band of the error signal e (n). It is good also as a structure which can set the frequency of the sound used as the object of active noise cancellation. As a result, it is possible not to reduce the sound of the frequency that the wearer of the headphones 20 desires to hear.

  Further, in the present embodiment, a reference microphone 36 disposed outside the housing 32 and a wall portion 37 interposed between the reference microphone 36 and the speaker 31 are provided. Based on the detected noise, sound is generated from the speaker 31 so that the input signal from the error microphone 33 is minimized. In the feedforward control using the reference microphone 36 at a position farther from the ear than the error microphone 33, the control is performed by referring to the noise at a position closer to the noise source than the error microphone 33. Time to reach can be earned, and responsiveness is assumed to be higher. Since high-frequency sound has a large phase change with time, higher responsiveness is required to reduce such sound. For this reason, the noise of a higher frequency can be reduced by performing feedforward control. In the above configuration, it is assumed that sound from the speaker 31 leaks to the outside of the housing 32 through the communication hole 40 of the housing 32. However, since the wall portion 37 is interposed between the reference microphone 36 and the speaker 31, it is possible to suppress a situation in which sound from the speaker 31 reaches the reference microphone 36. As a result, the reference microphone 36 can detect noise with less influence of the sound from the speaker 31, and can reduce noise more reliably.

  The housing 32 includes a bottom wall portion 38 that has a communication hole 40 and covers the speaker 31 from the side opposite to the ear 11, and a peripheral wall portion 39 that rises from the outer peripheral end of the bottom wall portion 38 toward the ear 11. The reference microphone 36 is disposed so as to overlap the bottom wall portion 38 from the side opposite to the ear 11, and the wall portion 37 is interposed between the reference microphone 36 and the bottom wall portion 38. Compared to the case where the reference microphone 36 is provided on the peripheral wall 39, it becomes easier to detect sound over the entire circumference in the circumferential direction of the housing 32.

<Embodiment 2>
Next, Embodiment 2 of the present invention will be described with reference to FIG. The same parts as those in the above embodiment are denoted by the same reference numerals, and redundant description is omitted. The headphone main body 230 of the present embodiment is different from the above-described embodiment in that the reference microphone 36 is provided on the peripheral wall 39 of the housing 32 as shown in FIG. In this embodiment, since the peripheral wall part 39 (an example of a wall part) is interposed between the reference microphone 36 and the speaker 31, the situation where the sound from the speaker 31 reaches the reference microphone 36 can be suppressed. As a result, only the noise can be reliably detected by the reference microphone 36, and the noise can be more reliably reduced.

<Embodiment 3>
Next, Embodiment 3 of the present invention will be described with reference to FIG. The same parts as those in the above embodiment are denoted by the same reference numerals, and redundant description is omitted. The headphone main body 330 of this embodiment does not include the reference microphone 36, and the configuration of the control unit is different from that of the above embodiment. The control unit 350 of the present embodiment constitutes a feedback type active noise canceling device together with the error microphone 33 and the speaker 31. As shown in FIG. 7, the control unit 350 of the present embodiment is a secondary path model 51, a noise control filter 53, a coefficient update unit 52, and a digital filter that simulates the acoustic transfer characteristics of the secondary path. And a synthesis unit 255 that synthesizes the error signal e (n) and the filtered pseudo noise signal z (n). In the secondary path model 254, the pseudo noise signal u (n) is filtered to generate a filtered pseudo noise signal z (n). The filtered pseudo noise signal z (n) is a signal corresponding to the pseudo noise (pseudo noise near the error microphone 33) from the speaker 31 that has passed through the secondary path.

  When noise is collected by the error microphone 33 and input as the error signal e (n), the error signal e (n) is input to the coefficient updating unit 52 and the combining unit 255. In the synthesizer 255, the error signal e (n) is added to the filtered pseudo noise signal z (n) and input to the secondary path model 51 and the noise control filter 53 as a reproduced noise signal d (n). . In the secondary path model 51, the reproduced noise signal d (n) is filtered so as to exclude the change in sound that occurs in the secondary path, and a filtered reproduced noise signal x (n) is generated. Is output. The coefficient updating unit 52 updates the coefficient used by the noise control filter 53 so that the error signal e (n) is minimized based on the filtered reproduced noise signal x (n) and the error signal e (n). The noise control filter 53 generates a pseudo noise signal u (n) by filtering the reproduced noise signal d (n) using the coefficient updated by the coefficient updating unit 52, and the pseudo noise signal u (n). ) Is output to the speaker 31. Thereby, the pseudo noise based on the pseudo noise signal u (n) is output from the speaker 31. This pseudo noise becomes a sound having an opposite phase to the noise at the position of the error microphone 33 after passing through the secondary path. The error microphone 33 detects a sound in which the noise and the pseudo noise overlap each other and is input as an error signal e (n), and the error signal e (n) is input to the coefficient updating unit 52. By repeating the above processing, the optimum pseudo noise is generated from the speaker 31 and the noise is canceled.

  The coefficient updating unit 52 updates the coefficient using, for example, a LMS (least mean square) algorithm. Thus, in this embodiment, noise can be reduced without using the reference microphone 36. In the present embodiment, a band limiting filter 62 (see FIG. 5) that performs filter processing for removing a specific frequency component from the error signal e (n) may be provided. According to the inventors of the present application, it has been confirmed that the feedback type active noise canceling apparatus exemplified in this embodiment can reduce noise of at least 300 Hz or less.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.
(1) In the above embodiments, the headphones for vehicles are exemplified, but the present invention is not limited to vehicles.
(2) In the first embodiment, the peripheral wall 39 of the housing may have a communication hole.
(3) In the said embodiment, it is good also as a structure which can change suitably the control by the control part 50 (control using a reference microphone and an error microphone) and the control by the control part 350 (control using an error microphone).
(4) The method for realizing active noise cancellation is not limited to that exemplified in the above embodiment. For example, a method that does not require a secondary path model (for example, simultaneous equation method or simultaneous perturbation method) can be used.

20 ... Headphone, 31 ... Speaker, 32 ... Housing, 33 ... Error microphone (ear-side microphone arranged on the ear side with respect to the housing), 36 ... Reference microphone (outside microphone arranged on the outside of the housing) , 37 ... wall part, 38 ... bottom wall part, 39 ... peripheral wall part (wall part interposed between outside microphone and speaker), 40 ... communication hole, 50, 350 ... control part

Claims (3)

A speaker, a housing that houses the speaker and covers an ear, an ear-side microphone disposed on the ear side with respect to the housing, and a control unit that controls driving of the speaker;
The housing has a communication hole that communicates the internal space of the housing and the external space of the housing.
The headphone having a configuration in which the control unit can reduce noise in the vicinity of the ear-side microphone by generating sound from the speaker based on an input signal from the ear-side microphone. An outer microphone arranged outside the housing, and a wall portion interposed between the outer microphone and the speaker,
The control unit generates sound from the speaker so that an input signal from the ear microphone as an error microphone is minimized based on noise detected by the outer microphone as a reference microphone. The listed headphones. The housing includes a bottom wall portion that has the communication hole and covers the speaker from the opposite side of the ear, and a peripheral wall portion that rises from the outer peripheral end of the bottom wall portion to the ear side,
The outer microphone is arranged so as to overlap the bottom wall portion from the side opposite to the ear,
The headphone according to claim 2, wherein the wall portion is interposed between the outer microphone and the bottom wall portion.

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