JPH0879873A - Communication terminal equipment - Google Patents

Abstract

PURPOSE: To obtain a communication terminal with performance sufficient for practical use in which a headphone to mounted on an external auditory is used to realize a clear sound output. CONSTITUTION: A headphone unit 6 and a microphone unit 10 are provided to a sound pipe 8. A voice signal from the microphone unit 10 is fed back from an input terminal 1 to a voice signal input system to the headphone unit 6 to form noise cancellation feedback circuit means (3, 4, 5, 6, 7, 10). Then an output means 14 to provide an output of the voice signal from the microphone unit 10 is provided. Furthermore, a subtractor 12 subtracting an input signal Sin from the sound signal from the microphone unit 10 and an equalizer 13 providing a prescribed characteristic to the sound signal are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication terminal and, more particularly, to a voice output using a microphone unit for feedback together with a headphone unit capable of performing feedback type noise cancellation. It was done like this.

[0002]

2. Description of the Related Art Generally, there is known a headphone (earphone) device which can be used by being attached to the ear canal and listening to an input voice. The headphone device is used to output the voice of the wearer. There are things you can do. This is shown in FIG. Reference numeral 50 denotes an earpiece portion to be attached to the ear canal, and a sound passage 51 is formed inside. Sound path 51
A speaker unit 52 is arranged at one end of the speaker unit 52, and an audio signal input from an input terminal 53 is amplified and supplied to the speaker unit 52 by an amplifier 54 and an audio is output. This is the normal earphone configuration.

In addition to this, a vibration sensor 55 is provided in the earpiece portion 50. This vibration sensor detects vibration in the ear canal when the wearer speaks,
The output of the vibration sensor 55 is amplified by the amplifier 56 and is output from the output terminal 57 as an audio signal emitted by the wearer. With this configuration,
The user can output sound without wearing a separate microphone by simply wearing this earphone.
In other words, this earphone functions as a voice signal transmitting / receiving terminal.

[0004]

However, in the detection by the vibration sensor, it is not possible to obtain the output audio signal with a degree of intelligibility that is satisfactory in actual use. For example, a voice with a small amount of vibration in the head of a speaker such as a consonant voice has been considerably unclear as an output voice signal.

[0005]

In view of the above problems, the present invention provides headphones (earphones) to be mounted on the ear canal.
It is intended to realize a clear voice output by using and to construct a communication terminal with sufficient performance in actual use.

For this reason, the headphone unit has its sound emitting surface on the sound tube having the inner diameter substantially the same as that of the external auditory meatus, one end side being the auricle mounting portion, and the other end side being the non-reflection end of the sound. Install it so that it faces the inside of the sound tube.
In addition, a microphone unit is installed so that the sound collecting surface faces the inside of the acoustic tube. Then, the audio signal from the microphone unit is fed back to the audio signal input system from the input means to the headphone unit to form a noise canceling type feedback circuit means. here,
Further, an output means for outputting a sound signal from the microphone unit is provided.

Further, there is provided subtracting means for subtracting the audio signal from the input means with respect to the audio signal from the microphone unit, and the output of the subtracting means is supplied to the output means for output.

The audio signal from the microphone unit is provided with a predetermined characteristic through the equalizer means, and then supplied to the output means for output.

[0009]

In the non-reflective headphone device having the acoustic tube, when the noise canceling feedback circuit means is formed, the microphone unit for feedback is mounted facing the inside of the acoustic tube. The speaking voice of the wearer is transmitted inside the head and vibrates the eardrum and the inner wall of the ear canal, so that a sound wave of the speaking voice is generated in the mounted acoustic tube. By extracting this sound wave using a microphone unit for feedback, an output audio signal with high clarity can be obtained, which can be realized as a communication terminal. Further, in order to further improve the output sound quality, the sound to be output is separated from the input sound signal from the sound collected by the microphone unit by the subtracting means, or the frequency characteristic is adjusted by the equalizer.

[0010]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 shows the structure of the communication terminal of the embodiment, and FIG. 2 shows its appearance. This communication terminal is used by connecting to a communication device (not shown).

In these figures, 1 is a voice input terminal. As shown in FIG. 2, the input terminal 1 is configured as one terminal of the plug 20 having a three-pole structure, for example. As the input audio signal S _in , the audio signal received by the communication device (not shown) to which the plug 20 is connected is supplied. Reference numeral 2 is an equalizer for adjusting the frequency characteristic of the input audio signal S _in , 3 is a subtractor, 4 is an equalizer, 5 is an amplifier, and 6 is a speaker unit. The audio signal S _in is equalized by the equalizer 2, the subtractor 3, the equalizer 4,
It is supplied to the speaker unit 6 via the amplifier 5 and output as sound.

Reference numeral 7 shown in FIGS. 1 and 2 is an acoustic tube having a long tubular shape, and an end portion 7b is an opening. A sound absorbing material 8 is filled inside. By attaching the speaker unit 6 to the acoustic tube 7, so-called non-reflection type headphones are configured. Speaker unit 6
Is attached to the acoustic pipe 7 with its sound emitting surface 6a facing the inside of the pipe. The acoustic tube 7 is formed as a long tube having an inner diameter W substantially equal to the inner diameter W ₀ of the external auditory meatus A, and an earpiece 9 is attached to one end portion 7a thereof. Also, the other end 7
b is an opening as a non-reflective end of the sound, and the sound absorbing material 8 is filled between the position near the speaker unit 6 and the end portion 7b.

The earpiece 9 attached to the end portion 7a of the acoustic tube 7 is made of a flexible synthetic resin or the like, and its tip can be inserted into the entrance portion C of the external auditory meatus A. The inner diameter of the earpiece 9 is set to W ₁ which is substantially the same as the inner diameter W of the acoustic tube 7 and the inner diameter W _{0 of the} ear canal.

The sound emitting surface 6a of the speaker unit 6 faces the inside of the acoustic tube 7 in a state of being substantially flush with the inner peripheral surface of the acoustic tube 7, and by doing so, the acoustic impedance characteristic of the acoustic tube 7 is improved. Speaker unit 6 without disturbing
Can be installed. Then, in a state where the distal end portion of the earpiece 9 is inserted into the entrance portion C of the external auditory meatus A and the acoustic tube 7 is attached, the distance from the eardrum B in the external auditory meatus A to the end portion 7b which is a non-reflective end between the sounds is substantially constant. By having the inner diameter of and continuing, the acoustic tube 7 becomes a sound path with a constant acoustic impedance.

With this configuration, the sound output from the speaker unit 6 is transmitted as a plane wave to both sides (end 7a side and end 7b side) in the acoustic tube 7. Of these, the sound wave that reaches the eardrum B and is reflected returns to the acoustic tube 7 side again, but because impedance matching is taken in the acoustic tube 7, the sound wave is not reflected elsewhere and ends in the acoustic tube 7. It is transmitted from the part 7a side to the end part 7b side. And end 7
It is gradually attenuated by the time it reaches b, and there is almost no sound at the end 7b. The acoustic tube 7 and the speaker unit 6 as described above prevent the headphone itself from generating a reflected sound. In addition, this non-reflection type headphone can obtain flat characteristics in a wide frequency band.

Reference numeral 10 is a microphone unit mounted toward the inner surface of the acoustic tube 7. Of course, this microphone unit 10 is also the speaker unit 6
Similarly to the above, the acoustic tube 7 is attached so as not to disturb the acoustic impedance characteristics of the acoustic tube 7. The output of the microphone unit 10 is supplied to the subtractor 3 and becomes a subtraction signal for the input signal S _in .

That is, the output of the microphone unit 10 is fed back to the signal input system, which constitutes a feedback type noise canceling circuit. In such a feedback type noise canceling headphone, the noise canceling operation principle is based on the feedback theory based on the board theorem.
That is, the amount of noise voice attenuation and the cancellation bandwidth are characterized by the open loop characteristics.

Considering the external noise P _in , the eardrum B
The sound pressure P _O to reach, due the nature of the feedback loop, P _O ≒ (1 / loop gain) × P _in next, i.e. noise reaches the tympanic membrane B was reduced by the loop gain component.

FIG. 2 shows the active noise attenuation (broken line) and the frequency characteristic of the closed loop response (solid line). The loop response to the input signal S _in is P _O = {(E · A · H) / (1 + E · A · H · M)} ×
S _in ≈ (1 / M) × S _in . However, E is the characteristic of the equalizer 4, A is the characteristic of the amplifier 5, H is the characteristic of the speaker unit 6, and M is the characteristic of the microphone unit 10. That is, the loop response to the input signal S _in is the feedback microphone unit 1
It depends on the characteristic M of zero. When the microphone unit 10 is an electret condenser microphone, its frequency characteristic is flat over a wide band, and thus the closed-loop characteristic has a straightforward characteristic as shown in FIG.

The equalizer 2 is for adjusting the variation of the frequency characteristic due to the influence of the feedback noise canceling loop so that the output voice has a flatter characteristic.

In this embodiment, the sound obtained by the microphone unit 10 is also used as the output sound signal. Therefore, the compensation circuit (equalizer) 1
1, a subtractor 12, an equalizer 13, and an output terminal 14 are provided. The output terminal 14 is configured as one terminal of a plug 20 having a three-pole structure as shown in FIG.

The voice of the wearer wearing this communication terminal is conducted in the head and vibrates the walls of the eardrum B and the ear canal A,
As a result, the sound pressure due to the speaking voice is generated in the external auditory meatus A. Here, when the non-reflective headphone including the acoustic tube 7 directly coupled to the external auditory meatus as described above is configured, a sound wave due to a speaking voice is generated in the acoustic tube 7, and the sound wave is picked up by the microphone unit 10. Will be. In other words, the audio signal picked up by the microphone unit 10 is
By being output as the signal S _out from the output terminal 14 via the equalizer 13, the voice of the wearer can be supplied to the connected communication device and transmitted to the outside.

By the way, the transmitted sound Se generated in the external auditory meatus A due to the vibration caused by the voice transmitted in the head has the frequency characteristic as shown in FIG. 4, and particularly in the high frequency range. For this reason, even if picked up by the microphone unit 10, the clarity is low when the output is performed as it is. In order to increase the clarity of the output audio signal, the above-mentioned noise canceling feedback loop functions complementarily, and the equalizer 1
Optimized in 3. Also, good two-way communication,
To prevent howling etc., input signal S _in and output signal S
There must be sufficient separation for _out . That is, not only the transmitted sound Se but also the output sound of the speaker unit 6 is picked up by the microphone unit 10, but this is output as it is as the output signal S _out.
This is because it is not suitable. For this purpose, a compensation circuit 11 and a subtractor 12 are provided.

These points will be described below. First, the external noise P _in is effectively attenuated by the feedback noise cancellation loop as described above. Therefore, the actual S / N ratio in the external auditory meatus A is improved by the reduction amount of the noise component,
The clarity of the transmitted sound Se is also improved.

Next, the separation by the compensation circuit 11 and the subtractor 12 is as follows. Input signal S
_in is output as an acoustic signal from the speaker unit 6 through the feedback type noise cancellation loop, and reaches the eardrum B. The microphone unit 10 picks up the transmitted sound Se and the acoustic output from the speaker unit 6. Here, the closed-loop transfer characteristic of the feedback loop covers the voice band with a sufficiently flat characteristic as shown in FIG. Therefore, the separation can be secured by subtracting the input signal S _in from the output of the microphone unit 10.

Considering the characteristic MSe of the audio signal picked up by the microphone unit 10, MSe = Se · M / (1 + G). In addition, G is an open loop gain by the equalizer 4, the amplifier 5, the speaker unit 6, and the microphone unit 10. The audio signal having the characteristic of this MSe is supplied from the microphone unit 10 to the subtractor 12. This characteristic MSe is substantially the same as the active noise attenuation characteristic of FIG.

The input signal S is converted from the voice signal having the MSe characteristic.
_A subtractor 12 is provided to separate the _in component. The input signal S _in passes through the compensation circuit 11 and the subtractor 1
2 and is subtracted from the audio signal from the microphone unit 10 in the subtractor 12. Compensation circuit 11
Shows the frequency characteristic of the input signal S _in as the characteristic MS
It is an equalizer for making it almost the same as e.

That is, the input signal S _in is given the same characteristics as the voice signal from the microphone unit 10, and the subtracter 12 subtracts the same characteristics, so that the subtractor 1
As the output of 2, the component of the input signal S _in is favorably canceled. The characteristics of the signal output from the headphone unit 6 and picked up by the microphone unit 10 are, for example, as shown in FIG.
Can be changed from the solid line state to the broken line state, and
Good separation of B or more can be obtained.

Further, the output of the subtractor 12 is the equalizer 13
_Is optimized as the output signal S _out . Equalizer 13
Then, the reverse characteristic to the characteristic of MSe, that is, the characteristic of (1 + G) / M 2 is given. Further, in order to correct the characteristic of the transmitted sound Se shown in FIG. 4, the high range is raised. As a result, the output of the equalizer 13 becomes a voice signal with high intelligibility and easy to hear.

As described above, in the present embodiment, a transmitter / receiver terminal of the type worn on the ear can be constructed, and the received voice (input signal S _in ) can be heard very clearly by the wearer by the noise canceling loop. Also, the transmitted voice (output signal S _out ) by the voice of the wearer can be a voice signal with high intelligibility. In other words, the output signal S _out is resistant to external noise such as wind noise and environmental noise due to the complementary action of the noise canceling loop, and the equalizer 13 corrects the clarity of the output signal S _out. it can. Furthermore, the separation from the input signal is good, and howling during communication is effectively prevented. There is also an advantage that propagation noise due to vibration of the cord is also attenuated.

In the embodiment, the communication terminal is assumed to transmit and receive monaural voice, but of course, the communication terminal of the present invention may be applied as 2-channel stereo headphones. Further, the present invention can be widely implemented as a transmitting / receiving unit in various communication devices such as mobile phones, wireless devices, and wired communication. Since it is particularly resistant to external noise, clear calls can be made even in noisy areas such as streets and factories. Further, since it is possible to make a call free by simply attaching it to one ear, it is suitable for a call during work at a factory or a work site, a call in a cockpit of an aircraft, and the like.

[0032]

As described above, the communication terminal of the present invention uses the microphone unit for noise canceling feedback to pick up and output the speaking voice transmitted through the wearer's head. The effect is that a hands-free communication terminal can be realized. In addition, the received sound (input signal) can be clearly heard by the wearer in the noise canceling loop, and the transmitted sound (output signal) caused by the wearer's voice is also affected by wind noise due to the complementary function of the noise canceling loop. It also has the effect of being clear and clear against external noise such as environmental noise.

Furthermore, by correcting the frequency characteristic of the output voice by the equalizer means, the clarity can be further improved. Further, by realizing the separation of the input signal and the output voice by the subtraction means, howling etc. at the time of communication can be effectively prevented.

As a result, clear two-way communication can be performed even in the presence of a large amount of external noise, and a communication terminal which is very convenient to carry can be realized.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a communication terminal of the present invention.

FIG. 2 is an explanatory diagram of an appearance example of an embodiment of a communication terminal of the embodiment.

FIG. 3 is an explanatory diagram of active noise attenuation characteristics and closed loop characteristics of the embodiment.

FIG. 4 is an explanatory diagram of frequency characteristics of human head transmitted sound.

FIG. 5 is an explanatory diagram of a separation characteristic of the example.

FIG. 6 is an explanatory diagram of a conventional headphone device capable of outputting sound.

[Explanation of symbols]

 1 Input terminal 2,4,13 Equalizer 3,12 Subtractor 5 Amplifier 6 Speaker unit 7 Acoustic tube 8 Sound absorbing material 9 Earpiece 10 Microphone unit 11 Compensation circuit 14 Output terminal 20 Plug part

Claims (3)

[Claims] 1. A headphone unit having a sound emitting surface for a sound tube having an inner diameter substantially the same as that of an ear canal, one end side of which is an auricle mounting portion and the other end side of which is a non-reflective end of sound. The microphone unit has a microphone unit mounted so as to face the inside of the acoustic pipe, and has a sound collecting surface facing the inside of the acoustic pipe. A voice signal from the microphone unit is input to an audio signal input system from the input unit to the headphone unit. A communication terminal comprising a noise canceling feedback circuit means for feeding back a signal and an output means for outputting an audio signal from the microphone unit. 2. A subtraction means for subtracting the audio signal from the input means with respect to the audio signal from the microphone unit is provided, and the output of the subtraction means is supplied to the output means for output. The communication terminal according to claim 1, wherein: 3. The communication terminal according to claim 1, wherein the voice signal from the microphone unit is configured to be supplied to the output means via an equalizer means and output.