JP2019087868A - Sound output device - Google Patents

Abstract

To restrain lowering of audibility of a target sound, when hearing the target sound together with the ambient sound at the time of wearing.SOLUTION: An earphone 10 includes a microphone 110 for collecting the ambient sound of a user, an equalizer 116 for imparting prescribed frequency characteristics to a first signal based on the sound collection of the microphone 110, a speaker 140 emitting sound toward the tympanic membrane of the user, a microphone 150 for collecting the sound near the speaker 140, an opposite phase signal generation circuit 156 for generating the opposite phase signal of the second signal based on the sound collection of the microphone 150 at a prescribed frequency or less, and an adder 130 for adding a target sound signal indicating the target sound, the opposite phase signal, and the output signal from the equalizer 116 and outputting toward the speaker. When target sound signal and the opposite phase signal are added by the adder 130, low range side of the target sound signal and the noise components, other than the output signal from the equalizer 116, out of the signal components collected by the microphone 150, is suppressed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to, for example, a sound output device.

  There is a demand for providing a function of hear through in sound output devices such as earphones and headphones. “Hear-through” refers to a function that allows the user to listen to ambient sounds as if they were not wearing the sound output device (see, for example, Patent Document 1).

JP-A-2015-537465

By the way, when the user wears an audio output device and listens for a target sound supplied from an external terminal such as a music player (hereinafter referred to as a "target sound") along with the surrounding sound, the audibility of the target sound is degraded. There is something to do.
The present invention has been made in view of the above-described circumstances, and it is an object of the present invention to reduce the audibility of the ambient sound when the user is wearing the audio output device and listening to the objective sound together with the ambient sound. It is in providing the technology to control.

  In order to achieve the above object, according to an aspect of the present invention, there is provided an audio output device including: a first microphone for picking up ambient sound of a user; and a first signal based on a sound collected by the first microphone. An equalizer for imparting frequency characteristics, a speaker for emitting sound toward the user's eardrum, a second microphone for collecting sound in the vicinity of the speaker, and a reverse-phase signal of a second signal based on the sound collected by the second microphone An adder for generating a phase-inverted signal generation circuit that generates a frequency equal to or less than a predetermined frequency, a target sound signal indicating a target sound, the phase-in-phase signal, and an output signal from the equalizer, and outputting the result toward the speaker. including.

It is a block diagram showing composition of an earphone concerning a 1st embodiment. It is a figure which shows the structure of an earphone. It is a figure which shows the wearing condition of an earphone. It is a figure which shows the headphones concerning 2nd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First Embodiment
FIG. 1 is a block diagram showing a configuration of an earphone 10 which is an example of the sound output device according to the first embodiment.
As shown in this figure, the earphone 10 includes microphones 110 and 150, amplifiers 112, 134 and 152, ADCs 114 and 154, an equalizer 116, an IF 122, an adder 130, a DAC 132, a speaker 140 and a reverse phase signal generation circuit 156. . When the earphone 10 is worn by the user, the sound emission direction of the speaker 140 is disposed in the direction toward the user's ear canal, and the microphone 150 is the sound emission direction of the speaker 140 and is acoustically coupled to the ear canal Placed in the

The microphone 110 (first microphone) picks up the ambient sound of the user wearing the earphone 10. The amplifier 112 amplifies the signal (first signal) collected by the microphone 110, and an ADC (Analog to Digital Converter) 114 converts the signal amplified by the amplifier 112 into a digital signal.
The equalizer 116 performs a correction process on the output signal of the ADC 114, for example, a process for compensating in advance a characteristic that is lost due to sound insulation when the earphone 10 is worn, and the signal subjected to the process is applied to the first input end of the adder 130. Supply.

An IF (InterFace) 122 is an interface that receives a signal from the external terminal 200 by radio. The signal received by the IF 122 is a signal reproduced by the external terminal 200, that is, a target sound signal of a sound to be heard by the user (target sound). The target sound signal received by the IF 122 is supplied to a second input end of the adder 130.
The target sound signal is, for example, a music signal reproduced by the external terminal 200. Further, the IF 122 may be configured to receive the target sound signal by wire instead of by wireless.

  The adder 130 adds the signals supplied to the first input end, the second input end, and the third input end, and supplies the result to a DAC (Digital to Analog Converter) 132. The DAC 132 converts the signal added by the adder 130 into an analog signal, and the amplifier 134 amplifies the signal converted by the DAC 132. The speaker 140 converts the signal amplified by the amplifier 134 into air vibration, that is, sound and outputs it.

  The microphone 150 (second microphone) is provided in the vicinity of the speaker 140 and picks up a sound or the like output from the speaker 140. The amplifier 152 amplifies the signal (second signal) collected by the microphone 150, and the ADC 154 converts the signal amplified by the amplifier 152 into a digital signal and supplies the digital signal to the negative phase signal generation circuit 156.

The negative phase signal generation circuit 156 is in the relation of inverting the phase of the output signal from the ADC 154, and generates a negative phase signal with substantially the same volume (amplitude) by adjusting the frequency, the amplitude and the phase. The negative-phase signal generation circuit 156 limits the generated negative-phase signal to, for example, a component whose frequency is 200 Hz or less by a built-in low-pass filter.
The frequency characteristics of the low pass filter are variable by setting the filter coefficient.

  Further, in FIG. 1, for example, when the equalizer 116, the adder 130 and the negative phase signal generation circuit 156 are configured by a DSP (Digital Signal Processor) integrated on one or two or more chips, for example, space saving can be achieved. .

FIG. 2 is a view showing the structure of the earphone 10.
As shown in this figure, the earphone 10 is, for example, canal type, and includes a housing 160 and an earpiece 180.
The housing 160 is generally cylindrical. In the internal space of the housing 160, a speaker 140 and microphones 110 and 150 are provided. In detail, the speaker 140 is attached so as to partition the internal space of the housing 160, and the sound emitting surface of the speaker 140 is directed to the ear canal.
The microphone 150 is attached closer to the ear canal (right side in the figure) of the space defined by the speaker 140 in the internal space of the housing 160.
The housing 160 is provided with one or more vent holes 168 for ventilating the outside in a space near the external ear canal among the internal space partitioned by the speaker 140 when worn.
On the other hand, the microphone 110 is provided on the opposite side of the space on the side opposite to the ear canal in the internal space partitioned by the speaker 140.

  The earpiece 180 is made of an elastic material such as polyvinyl or sponge, and formed into a hollow cannonball shape opened at the opening 186 so as to be removable from the ear canal side of the housing 160. When the earpiece 180 is attached to the housing 160, the opening 186 communicates with the internal space of the housing 160.

  Of the components of the earphone 10 shown in FIG. 1, components other than the microphones 110 and 150 and the speaker 140 are provided in the internal space of the housing 160, for example, in the vicinity of the microphone 110, but are omitted in FIG. ing.

  FIG. 3 is a view showing a wearing state of the earphone 10, and more specifically, a view showing the earphone 10 being worn on the right ear of the user W. As shown in FIG. As shown in this figure, the earpiece 180 of the earphone 10 is inserted into the ear canal 314. Specifically, the earpiece 180 is inserted into the ear canal 314 with the opening 186 directed to the tympanic membrane 312, while a portion of the housing 160 is exposed from the ear canal 314.

Next, the operation of the earphone 10 will be described.
As shown in FIG. 3, when the earphone 10 is worn by the user W, the speaker 140 receives the addition signal from the adder 130, and more specifically, the signal of the ambient sound picked up by the microphone 110 and the external terminal 200. The sound is produced based on the addition signal of the target sound signal supplied from the signal and the reverse phase signal.

  The negative phase signal generation circuit 156 outputs a negative phase signal of a component whose frequency is 200 Hz or less among the signals collected by the microphone 150. For this reason, when the speaker 140 generates a sound based on the added signal, it reaches the eardrum 314 in a state in which the component having a frequency of 200 Hz or less is suppressed among the signals of the surrounding sound. In addition, as ambient sound suppressed by the said reverse phase signal, mechanical noise, such as a blowing noise and an engine, is mentioned, for example.

  As described above, the user wearing the earphone 10 perceives the noise of the low frequency component of the ambient sound in a canceled (suppressed) state. Therefore, according to the earphone 10, the low frequency part of the sound based on the target sound signal, in particular the rhythm sound, is not masked by the peripheral sound, so that the audibility of the sound based on the target sound signal can be improved. .

By the way, when the earphone 10 is not worn, the user W vibrates the tympanic membrane 312 via the ear canal 314 (air) to transmit airborne sound transmitted to the auditory nerve and vibration transmitted through the skin, bones, etc. It perceives by the addition with the bone conduction sound transmitted to the nerve. Note that the bone conduction sound includes a voice that is perceived as the vibration of the vocal cords of the person is transmitted to the auditory nerve through the bone or the like.
As shown in FIG. 3, when the earphone 10 is worn by the user W, the sound is perceived by the sum of the sound emitted from the speaker 140, the sound leaking into the ear canal 314 via the vent 168 and the bone conduction sound. Do.
The sound emitted from the speaker 140 when the earphone 10 is worn is different from that when the earphone 10 is not worn due to the obstruction / insulation of the external ear canal 314. To reach. However, since the ambient sound signal picked up by the microphone 110 is compensated in advance for loss due to blocking / insulation by the earpiece 180 at the time of wearing by the compensation processing of the equalizer 116, the user W hears the sound emitted from the speaker 140 Among them, the ambient sound can be perceived as natural as if the earphone 10 is not worn.

  As described above, according to the earphone 10, while the audibility of the sound based on the target sound signal is improved, it is possible to perceive the peripheral sound with a natural feeling.

By the way, processing such as digital conversion and filtering is performed until the signal collected by the microphone 150 is reverse-phased by the negative-phase signal generation circuit 156 and supplied to the third input terminal of the adder 130 as a negative-phase signal. Go through. For this reason, the anti-phase signal does not strictly have an anti-phase relationship with the leaked ambient sound.
In particular, for peripheral sounds with high frequency (short period) and peripheral sounds without periodicity, the degree of suppression is small even if antiphase signal is added, or noise is emphasized instead of being suppressed. There are times when

So, in this embodiment, the object of suppression is made into the component below a predetermined frequency. However, if the upper limit frequency to be suppressed is high, the ambient sound is excessively suppressed, and the ambient sound heard by the user becomes unnatural. On the other hand, when the upper limit frequency to be suppressed is low, the low frequency part of the sound based on the target sound signal is excessively masked by the peripheral sound which is not suppressed (perceived by the user), so listening to the sound based on the target sound signal Sex is reduced.
For this reason, in the present embodiment, the upper frequency limit of the negative phase signal is set to 200 Hz to set the target of suppression in order to set the low frequency band of the music rhythm sound to the extent that the peripheral sound is not masked while considering both balance. It is below the frequency.

  In the present embodiment, the upper limit frequency of the reverse phase signal is 200 Hz. However, since the human sense of hearing has variations, it can not be avoided to have a certain frequency range. Further, even the low pass filter in the negative phase signal generation circuit 156 naturally generates an error. For this reason, in the present case, it is acceptable that the upper limit frequency of the negative phase signal is accompanied by a certain range (160 to 240 Hz) as around 200 Hz.

Also, in general, since the lowest fundamental sound of men is 180 Hz and the lowest fundamental sound of women is 220 Hz, if the component of the lowest fundamental sound is suppressed, the speech sound may be unnaturally heard.
Therefore, in the case of emphasizing the audibility of conversational sound as the peripheral sound, the negative phase signal generation circuit 156 may generate a negative phase signal that suppresses noise with a frequency of 150 Hz or less.
The reason why the frequency of 180 Hz or less is not used but 150 Hz which is lower than that is because the margin of the response characteristic of the low pass filter is taken into consideration.

  In the embodiment, although the case where the earphone 10 is worn on the right ear has been described as an example, it may be worn on the left ear. In addition, two earphones 10 having the same configuration are prepared, one for the right ear and the other for the left ear, and the left signal of the stereo is worn for the earphone worn for the left ear and the right ear is worn The stereo right signal may be supplied from the external terminal 200 to the earphones 10, respectively.

Second Embodiment
Although the earphone 10 is illustrated as the sound output device in the above-described embodiment, the embodiment can also be applied as a headphone.

FIG. 4 is a view showing the configuration of a headphone 1 which is an example of the sound output device according to the second embodiment.
As shown in this figure, the headphone 1 includes headphone units 10L and 10R, a headband 3, and arms 4L and 4R. The headband 3 has a shape in which a circular arc is drawn in the longitudinal direction by a metal or a resin having elasticity. Of the two ends of the headband 3, the headphone unit 10L for the left ear is attached to one end (left in the drawing) via the arm 4L, and the arm 4R is attached to the other end (right on the drawing). A headphone unit 10R for the right ear is attached.

The headphone unit 10 </ b> L includes a substantially cylindrical housing 160 and an ear pad 182 attached to the housing 160. The electrical configuration of the headphone unit 10L is the same as the above-described earphone 10, and includes the microphones 110 and 150 and the speaker 140, respectively.
The headphone unit 10R has substantially the same configuration as the headphone unit 10L.
A stereo left signal is supplied to the headphone unit 10L, and a stereo right signal is supplied to the headphone unit 10R from the external terminal 200.

  When wearing the headphone 1, the user holds the headphone units 10L and 10R and spreads the arc of the headband 3, while the ear pad 182 of the headphone unit 10L is to the left and the ear pad 182 of the headphone unit 10R is to the right. Put on each. The elasticity of the headband 3 generates a restoring force that brings the ends of the headband 3 close to each other. For this reason, the headphone units 10L and 10R located at the end of the headband 3 apply lateral pressure to the head of the user when worn. The headphone 1 is held at a predetermined position by this side pressure.

When the headphone 1 is worn by the user, the ear pad 182 shields the ear. The transmission of sound is substantially the same as that of the earphone 10.
For this reason, according to the headphone 1, it is possible to allow the user to perceive the ambient sound in a natural way while improving the audibility of the sound based on the stereo target sound signal.

<Example of application / modification>
In the embodiment, a plurality of sets of filter coefficients for the low-pass filter in the negative phase signal generation circuit 156 are prepared, and any one set is matched to the type of music (genre), the surrounding environment, the preference of the user, etc. It is good also as composition selected suitably and using it. That is, the negative phase signal generation circuit 156 may be configured to switchably generate the upper limit frequency of the negative phase signal in the range of 200 Hz or less.

<Supplementary Note>
For example, the following aspects can be grasped from the above-described embodiment and the like.

<Aspect 1>
A sound output device according to a preferred aspect 1 of the present invention is a first microphone for picking up ambient sound of a user, and an equalizer for giving a predetermined frequency characteristic to a first signal based on the sound picked up by the first microphone. A speaker emitting sound toward the tympanic membrane of the user, a second microphone for collecting sound in the vicinity of the speaker, and a reverse phase signal of a second signal based on the sound collected by the second microphone at a frequency of 200 Hz or less And an adder for adding a target sound signal indicating a target sound, the negative phase signal, and an output signal from the equalizer and outputting the result to the speaker.
According to the sound output apparatus of the first aspect, when the user listens to the target sound together with the surrounding sound, it is possible to suppress the audibility of the surrounding sound from being degraded.

<Aspect 2>
An acoustic output device according to a second aspect is the acoustic output device according to the first aspect, wherein the negative phase signal generation circuit generates the negative phase signal at a frequency of 150 Hz or less. According to the sound output device of aspect 2, the audibility of speech sound is improved.

<Aspect 3>
An acoustic output device according to a third aspect is the acoustic output device according to the first aspect or the second aspect, wherein the negative phase signal generation circuit switchably generates the upper limit frequency of the negative phase signal. According to the sound output device of aspect 3, according to the type of music (genre), the surrounding environment, the preference of the user, etc.
The audibility of the target sound and the surrounding sound can be selected.

DESCRIPTION OF SYMBOLS 1 ... Headphones, 10 ... Earphone, 110 ... Microphone (1st microphone), 116 ... Equalizer, 130 ... Adder, 140 ... Speaker, 150 ... Microphone (2nd microphone), 156 ... Reversed-phase signal generation circuit, 200 ... External Terminal.

Claims (3)

With the first microphone to pick up the ambient sound of the user,
An equalizer for imparting a predetermined frequency characteristic to a first signal based on sound pickup of the first microphone;
Speakers that emit sound toward the user's tympanic membrane,
A second microphone for picking up sound in the vicinity of the speaker;
A negative phase signal generation circuit that generates a negative phase signal of the second signal based on the sound collection of the second microphone at a predetermined frequency or lower;
An adder for adding a target sound signal indicating a target sound, the negative phase signal, and an output signal from the equalizer, and outputting the result to the speaker;
Sound output device including. The sound output device according to claim 1, wherein the negative phase signal generation circuit generates the negative phase signal at a frequency of 200 Hz or less. The sound output device according to claim 1, wherein the negative phase signal generation circuit switchably generates an upper limit frequency of the negative phase signal.

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