JP2019003126A - headphone - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve noise canceling performance in headphones while suppressing an increase in power consumption of headphones. SOLUTION: Headphones are based on a driver unit, a plurality of microphones provided on the circumference of a concentric circle centered on the center position of the driver unit, and a plurality of sounds detected by the plurality of microphones. A sound specifying unit that specifies a sound between the maximum sound of a plurality of sounds and the minimum sound of the plurality of sounds, a sound generating unit that generates a canceling sound that cancels the sound specified by the specific unit, and a sound generating unit. Has. [Selection diagram] Fig. 1

Description

  The present invention relates to headphones having a noise canceling function.

  There is known a feedback type headphone that generates a noise cancellation signal having a phase opposite to that of external noise detected by a microphone and reduces external noise heard by the user (see, for example, Patent Document 1).

JP 2004-163875 A

  Since the position where the microphone is provided is far from the position of the human eardrum, there is a difference between the external noise entering the microphone and the external noise reaching the human eardrum. As a result, there is a difference between the noise cancellation signal and the external noise reaching the human eardrum and the signal having the opposite phase, and there is a problem that the external noise that cannot be removed by the noise cancellation signal remains. When there is a specific frequency whose difference is extremely large, the noise cancellation signal output from the driver unit remains in the casing without being canceled, and howling may occur when the microphone collects the signal again.

  As a method to solve this problem, an analog filter or digital filter is applied to the sound signal including the external noise collected by the microphone to absorb the difference between the external noise entering the microphone and the external noise reaching the human eardrum. It has been tried to do. However, since the frequency characteristics of this difference are complicated, a multi-order active filter is required when an analog filter is used, and the number of filter stages increases when a digital filter is used, resulting in consumption due to an increase in circuit scale and processing. This leads to an increase in power.

  For example, when a plurality of microphones are used like the headphones disclosed in Patent Document 1, it is necessary to adjust the respective gains and phases of the external noise detected by the plurality of microphones in the bandpass controller, and the circuit scale And the power consumption accompanying the increase in processing will increase.

  Therefore, the present invention has been made in view of these points, and an object thereof is to improve noise cancellation performance in headphones while suppressing an increase in power consumption of a circuit due to filter processing of an analog filter or a digital filter. .

  The headphones of the present invention are based on a driver unit, a plurality of microphones provided on a circumference of a concentric circle centering on a center position of the driver unit, and a plurality of sounds detected by the plurality of microphones. A sound specifying unit that specifies a sound between the maximum sound of the plurality of sounds and a minimum sound of the plurality of sounds, a sound generating unit that generates a canceling sound that cancels the sound specified by the sound specifying unit, Have For example, the sound specifying unit specifies an average value of the plurality of sounds as a loudness between the maximum sound and the minimum sound.

  The plurality of microphones may be provided at equal intervals on the circumference. The plurality of microphones may be provided between the outer periphery of the driver unit and the inner periphery of the ear pad.

  According to the present invention, it is possible to improve noise cancellation performance in headphones while suppressing an increase in power consumption of a circuit due to filter processing of an analog filter or a digital filter.

It is a figure which shows the structure of headphones. It is a figure for demonstrating the generation method of a noise cancellation sound. It is a figure for demonstrating the experiment method for confirming the effect of the headphones of this Embodiment. It is a figure which shows the difference of the reference | standard sound detected with the microphone for a measurement, and the sound detected with each of the several microphone for feedback. It is a figure which shows the result of having compared the noise cancellation performance in the headphones of this Embodiment with the noise cancellation performance of the conventional headphones.

[Outline of headphones 1]
FIG. 1 is a diagram illustrating a configuration of a headphone 1 according to the present embodiment. FIG. 1A is a diagram schematically illustrating a state where the user U wearing the headphones 1 is viewed from the left side. FIG. 1B is a diagram showing the configuration of the ear cup 2 of the headphones 1. FIG. 1B shows a configuration of the ear cup 2 as viewed from the side in contact with the user U.

  The ear cup 2 includes a housing 11, a driver unit 12, and an ear pad 13. The housing 11 is substantially circular, and a driver unit 12 is fixed near the center. The ear pad 13 is fixed near the outer periphery of the housing 11.

  The housing 11 is provided with a plurality of feedback microphones 21 (21a, 21b, 21c, 21d) for detecting external noise used to generate a noise cancellation signal for canceling the external noise. The plurality of microphones 21 have the same characteristics, and convert incoming sound into an electrical signal. The plurality of microphones 21 are provided on a concentric circle centered on the center position of the driver unit 12. For example, four microphones 21 are arranged at equal intervals on a concentric circle.

  The plurality of microphones 21 are provided between the outer peripheral contour line of the driver unit 12 and the inner peripheral contour line of the ear pad 13. For example, the plurality of microphones 21 are provided at positions equidistant from the outer peripheral contour line of the driver unit 12 and the inner peripheral contour line of the ear pad 13. Since the plurality of microphones 21 are provided concentrically as described above, sound emitted from the driver unit 12 reaches each of the plurality of microphones 21 with the same magnitude and the same phase, and It is possible to minimize the difference in the influence of sound reflection by the ear pad 13 that each microphone 21 receives.

[Method of generating noise canceling sound]
FIG. 2 is a diagram for explaining a method of generating a noise canceling sound. As shown in FIG. 2, the headphone 1 includes a sound specifying unit 31 and a sound signal generating unit 32 in order to generate a noise canceling sound. The sound signal generating unit 32 functions as a sound generating unit that generates a noise canceling sound in conjunction with the driver unit 12.

  The sound specifying unit 31 specifies a sound between the maximum sound of the plurality of sounds and the minimum sound of the plurality of sounds based on the plurality of sounds detected by the plurality of microphones 21. For example, the sound specifying unit 31 specifies an average value of a plurality of sounds input from the plurality of microphones 21 as a loudness between the maximum sound and the minimum sound. Specifically, the sound specifying unit 31 synthesizes a plurality of electric signals input from the plurality of microphones 21 and attenuates the electric signals, thereby corresponding to an average value of the amplitudes of the sounds detected by the plurality of microphones 21. A signal (hereinafter referred to as an average value signal) is generated. The sound identification unit 31 inputs the generated average value signal to the sound signal generation unit 32.

  The sound signal generating unit 32 generates a noise cancellation signal based on the average value signal input from the sound specifying unit 31. Specifically, the sound signal generation unit 32 generates a noise cancellation signal for generating a noise cancellation sound that cancels the plurality of sounds detected by the plurality of microphones 21 by inverting the phase of the average value signal.

  The sound signal generation unit 32 inputs the generated noise cancellation signal to the driver unit 12. Specifically, the sound signal generating unit 32 inputs an electric signal having a magnitude corresponding to the average value input from the sound specifying unit 31 to the driver unit 12. The driver unit 12 generates a noise canceling sound based on the input noise canceling signal. For example, assuming that the sound levels output from four microphones 21a, 21b, 21c, and 21d are La, Lb, Lc, and Ld, the average value signal is (La + Lb + Lc + Ld) / 4 appropriately adjusted (for example, attenuated). A) signal.

[Effect confirmation experiment]
FIG. 3 is a diagram for explaining an experimental method for confirming the effect of the headphones 1 of the present embodiment. In this experiment, a dummy head H (HATS) is used as a measurement jig simulating a human head. The dummy head H has a measurement microphone 3 inside the pseudo ear shell. The signal collected by the measurement microphone 3 corresponds to a signal that reaches the human eardrum position. With the headphones 1 of the present embodiment mounted on the dummy head H, pink noise was passed from the speaker 4 and the sound levels detected by the measurement microphone 3 and the plurality of microphones 21 were measured.

  FIG. 4 is a diagram illustrating the difference between the reference sound detected by the measurement microphone 3 and the sound detected by each of the plurality of feedback microphones 21. 4 (a), 4 (b), 4 (c) and 4 (d) respectively show the loudness detected by the microphones 21a, 21b, 21c and 21d and the loudness of the reference sound (hereinafter, referred to as “the loudness of the reference sound”). The difference from the reference value is shown for each frequency. FIG. 4E shows the difference between the sound value detected by the microphone 22 provided at the position closest to the measurement microphone 3 and the reference value, which are equidistant from the microphones 21a, 21b, 21c, and 21d. ing.

  As shown in FIGS. 4A to 4E, it can be seen that if the position of the microphone is different, the difference from the reference value is also different. For example, in FIGS. 4A and 4B, the sound level detected by the microphone 21a and the microphone 21b between 10 kHz and 11 kHz is smaller than the reference value, whereas FIGS. In FIG. 4D, the sound level detected by the microphone 21c and the microphone 21d is equal to or higher than the reference value.

  In such a case, the average value of the sound detected by the microphones 21a, 21b, 21c, and 21d is closer to the reference value than the value of the sound detected by the microphones 21a, 21b, 21c, and 21d. Thus, even if there is a difference between the sound detected by each of the microphones 21a, 21b, 21c, and 21d and the reference sound, the sound specifying unit 31 is detected by the microphones 21a, 21b, 21c, and 21d. It is considered that a sound close to the sound detected by the human ear can be specified by using the average value of the sound.

  FIG. 5 is a diagram showing a result of comparing the noise cancellation performance of the headphones 1 of the present embodiment with the noise cancellation performance of conventional headphones. The dashed-dotted line in FIG. 5 has shown the noise cancellation performance of the conventional headphones in which only one microphone is used. The solid line in FIG. 5 indicates the noise cancellation performance of the headphones 1 that uses the average value of the sounds detected by the microphones 21a, 21b, 21c, and 21d as the external noise sound.

  In the region a of FIG. 5, the noise cancellation capability of the conventional headphones is about 7.5 dB at the maximum, whereas the noise cancellation capability of the headphones 1 of the present embodiment is about 16 dB at the maximum. . In addition, in the case of using conventional headphones, it can be seen that noise increases at a specific frequency in the region b of FIG.

  In general, a noise canceling effect can be obtained in a range from 20 Hz to 2 kHz by increasing the gain of the microphone. However, in the conventional headphones, the difference between the sound detected by the feedback microphone and the sound detected by the measurement microphone 3 at a specific frequency becomes large, so that the howling margin is small and the noise canceling performance is reduced. Therefore, the gain of the feedback microphone cannot be increased. Before the expected noise cancellation effect is obtained, howling occurs in the high frequency range, and the gain of the feedback microphone cannot be increased. As a result, the noise cancellation effect in the low frequency range cannot be obtained sufficiently. Conceivable.

  On the other hand, in the headphone 1, by synthesizing and averaging sounds detected by the microphones 21a, 21b, 21c, and 21d, it is possible to suppress an extremely large difference from the reference sound at a specific frequency. . As a result, howling that has occurred when only one microphone is used is less likely to occur. Therefore, by increasing the gain of the microphone, noise cancellation performance can be improved as indicated by the solid line in FIG. it can.

[Modification 1]
In the above description, in order to specify the sound between the maximum sound and the minimum sound among the plurality of sounds detected by the plurality of microphones 21, the sound specifying unit 31 combines the plurality of sounds and calculates the average value. However, the sound specifying unit 31 may use a value other than the average value as the value of the sound between the maximum sound and the minimum sound. The sound specifying unit 31 may use, for example, a median value of a plurality of sound values detected by the plurality of microphones 21 as a sound between the maximum sound and the minimum sound. In the present embodiment, four microphones 21 are provided on the ear cup 2. In this case, the sound identification unit 31 may use the second or third loudest sound as the sound between the maximum sound and the minimum sound at each frequency.

[Modification 2]
The sound specifying unit 31 may combine the plurality of sounds detected by the plurality of microphones 21 as they are without synthesizing them, and weighting each sound. For example, the sound specifying unit 31 performs weighting based on the distance between the microphone 21 and the inner contour line of the ear pad 13. Specifically, when the ear pad 13 is not circular, the sound specifying unit 31 determines the weight of the sound detected by the microphone 21 that is long from the ear pad 13 and is not easily affected by the reflection of the sound from the ear pad 13. Is made larger than the sound weight detected by the short microphone 21. By doing in this way, the influence of reflection by the ear pad 13 can be reduced in the sound used for generating the noise canceling sound.

[Effects of the headphones 1 of the present embodiment]
As described above, in the headphone 1, a plurality of feedback microphones 21 are provided on a concentric circle centered on the center position of the driver unit 12. Then, the sound signal generator 32 generates a noise canceling sound based on the sound between the maximum sound and the minimum sound among the plurality of sounds detected by the plurality of microphones 21. In this way, in the headphone 1, errors caused by the position of the feedback microphone being different from the position of the human eardrum can be reduced, and the noise cancellation performance can be improved over a wide frequency range.

  The plurality of microphones 21 are provided at equal intervals on a concentric circle. Since the plurality of microphones 21 are provided at equal intervals, the tendency of the sound detected by the plurality of microphones 21 is not biased. Therefore, the difference between the average value of the sounds detected by the plurality of microphones 21 and the value of the reference sound Can be reduced.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment, A various deformation | transformation and change are possible within the range of the summary. is there. For example, the specific embodiments of device distribution / integration are not limited to the above-described embodiments, and all or a part of them may be configured to be functionally or physically distributed / integrated in arbitrary units. Can do. In addition, new embodiments generated by any combination of a plurality of embodiments are also included in the embodiments of the present invention. The effect of the new embodiment produced by the combination has the effect of the original embodiment.

DESCRIPTION OF SYMBOLS 1 Headphone 2 Ear cup 3 Measurement microphone 4 Speaker 11 Housing 12 Driver unit 13 Ear pad 21 Microphone 22 Microphone 31 Sound specific part 32 Sound signal generation part

Claims (4)

A driver unit;
A plurality of microphones provided on the circumference of a concentric circle centering on the center position of the driver unit;
Based on a plurality of sounds detected by the plurality of microphones, a sound specifying unit that specifies a sound between a maximum sound of the plurality of sounds and a minimum sound of the plurality of sounds;
A sound generating unit that generates a canceling sound that cancels the sound specified by the sound specifying unit;
Having headphones. The sound specifying unit specifies an average value of the plurality of sounds as a sound volume between the maximum sound and the minimum sound;
The headphones according to claim 1. The plurality of microphones are provided at equal intervals on the circumference.
The headphones according to claim 1 or 2. The plurality of microphones are provided between an outer periphery of the driver unit and an inner periphery of the ear pad.
The headphones according to any one of claims 1 to 3.

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