JPH03214892A - Noise reducing device - Google Patents

Abstract

PURPOSE:To effectively reduce external noise without oppressing the side part of a head by using the constitution which reverses the phase of the external noise within an acoustic tube sound-absorbed with an internal microphone unit and allows an earphone unit to be pronounced. CONSTITUTION:This noise reducing device is constituted of an acoustic tube 1 for which an inside diameter W is formed approximately the same as the inside diameter W0 of an external auditory canal A and an ear attaching part 4 is provided on one end side and a sound absorbing material is provided on the other end side, an earphone unit 3 and an internal microphone unit 6 fitted proximately each other. A reception signal, etc., through an input terminal 7 are supplied to the unit 3 through an equalizer 8, an adder 9, a control circuit 10 and an amplifier 11. The unit 3 pronounces an output signal from the amplifier 11 as reproducing sound. An adder 12 adds reproducing voice which is pronounced from the unit 3 and arrives at the external auditory canal A and external noise N. The added reproducing voice is sound-absorbed with the unit, the unit 6 reverses the phase of the voice and is supplied to the adder 9. The adder 9 adds the signals from the unit 6 and the equalizer 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a noise reduction device for reducing external noise, which is commonly used in high noise environments such as inside a vehicle or at a construction site.

[Summary of the invention]

The noise reduction device according to the present invention includes an acoustic tube formed to have approximately the same inner diameter as the external auditory canal, one end of which is an auricle attachment portion, and the other end of which is a non-reflection end for sound. An earphone unit and an internal microphone unit are provided in the vicinity of the sound tube, and are mounted close to each other on the circumferential surface of the acoustic tube with their respective vibration surfaces facing inward of the tube, and the earphone unit and the internal microphone unit are installed in close proximity to each other on the circumferential surface of the acoustic tube, with each vibrating surface facing inward of the tube. By inverting the phase of the external noise inside the acoustic tube and producing sound through the earphone unit, the external noise is reduced so that good reproduced sound can be heard.

[Conventional technology]

BACKGROUND ART Conventionally, so-called earmuff-type devices have been widely known as noise reduction devices used for work in places with strong external noise. This earmuff-type noise reduction device is worn by covering the ears with a headphone cup to reduce external noise, and by pressing the headphone cup against the side of the head, the headphone cup and the side of the head are connected. It was used to prevent external noise from entering the space.

[Invention tries to solve! l#! ff) However, with the conventional noise reduction device described above, in order to prevent external noise from the surroundings from entering between the headphone cassock and the side of the head, it is necessary to press the headphone cup firmly against the side of the head. This creates a feeling of pressure on the temporal region of the head, and the noise reduction device itself is large and heavy, making it difficult to withstand long-term use.

In addition, with just the headphone cup, the low range of noise (several hundred
For example, if you try to reduce the noise using the method described above and listen to the reproduced sound, the reflection of the reproduced sound within the headphone cup will cause what is called an in-head localization phenomenon. However, this in-head localization phenomenon is caused by the fact that when looking at the sound source from the ear canal, the acoustic impedance at the entrance of the ear canal is different from the impedance inside the ear canal. Reflection occurs between the cup and the entrance to the ear canal, and this reflected wave returns to the eardrum.
This is a phenomenon in which a sound image is localized in the head, causing an unpleasant sensation similar to that of a stuffy ear. The present invention has been made in view of the above-mentioned problems, and has been developed to withstand long-term use without causing intrahead localization phenomenon or putting pressure on the temporal region, and to effectively reduce external noise. The purpose of the noise reduction device 1 is to provide a noise reduction device 1 (Means for solving the problem) The noise reduction device according to the present invention is formed to have an inner diameter substantially the same as that of the external auditory canal, and has one end serving as an auricle attachment portion, Acoustic tubes, the other end of which is the non-reflective end for sound, are installed near the ears when worn, and are attached close to each other on the circumferential surface of the acoustic tube with each vibration surface facing inward. It has an earphone unit and an internal microphone unit, and is characterized in that the external noise is reduced by inverting the phase of external noise in the acoustic tube that is picked up by the internal microphone unit and generating sound with the earphone unit. [Function] The noise reduction device according to the present invention is formed to have approximately the same inner diameter as the external auditory canal, one end is used as the auricular attachment part, and the other end is used as the end that does not reflect sound. The vibrations of the earphone unit and the internal microphone unit are mounted close to each other on the circumferential surface of the acoustic tube so as to face the inside of the tube. By inverting the phase of the sound and emitting sound using the earphone Uninote, external noise can be effectively reduced without putting pressure on the temporal region of the head, causing discomfort such as a feeling of pressure even when used for a long time. [Example] Examples of the noise reduction device according to the present invention will be described below with reference to the drawings. Fig. 1 is a sectional view of the noise reduction device according to the present invention when installed. In Figure 1, the noise reduction device has an inner diameter W of the external auditory canal A.
The auricle mounting member 4 is formed to have an inner diameter W that is approximately the same as o, and one end is provided with a flexible auricle attachment member 4 made of synthetic resin, rubber, etc., and the other end is made of felt, for example, so that the sound does not reflect. An acoustic tube 1 provided with a sound absorbing material 5 such as
It consists of an earphone unit 3 and an internal microphone unit 6, which are mounted close to each other on the circumferential surface of the tube, with their respective vibrating surfaces facing inside the tube. The acoustic tube l serves as an earphone housing, and has a uniform inner diameter W and is approximately the same as the inner diameter Wo of the outer ear tube A, and has a sound absorbing material 5 on the other end side so as to form an end that does not reflect sound. By providing
The acoustic impedance of the acoustic tube 1 is made to be approximately the same as the impedance of the external auditory canal A, and is configured to prevent the so-called intrahead localization phenomenon. Also, in order to prevent this change in acoustic impedance, the earphone unit 3. Internal microphone unit 6 is acoustic tube 1
so that each diaphragm is parallel to the side of the
The cross-sectional area S1 of the acoustic tube l is the same as that of the earphone unit 3. Each cross-sectional area S of the attachment part of the internal microphone unit 6!
．． It is installed so that it is almost the same as S3. Second
The figure shows a specific block diagram of the noise reduction device. In FIG. 2, for example, a received signal is supplied to an equalizer 8 via an input terminal 7. As shown in FIG.

The equalizer 8 enhances the audio portion of the received signal by raising the frequency of the received signal, for example, and outputs the signal while emphasizing the audio portion of the received signal. This output signal is supplied to a control circuit 10 via an adder 9, which will be explained later. Note that the frequency adjustment in the equalizer 8 may be performed by any level adjustment. The control circuit 10 connects the equalizer 8 to the earphone unit 3.
The entire circuit up to this point controls the frequency characteristics of the output signal supplied via the adder 9 so as to correspond to the acoustic frequency characteristics of the external noise while it reaches the ear. The output signal from the control circuit 10 is supplied to the earphone unit 3 via the amplifier ll. Note that the amplifier 1l may have a variable amplification factor in order to make it easier to listen to the reproduced audio.

The earphone unit 3 performs electro-acoustic conversion on the supplied output signal from the amplifier 11 and produces sound as reproduced sound.

Here, the adder 12 is connected to the reproduced sound which is emitted from the earphone unit 3 and reaches the ear canal A, and which is supplied from the input terminal 13 via the earphone unit 3 or the acoustic tube 1 or to the earphone unit 3. and the external noise that reaches the ear canal A from the gap between the ears. This is expressed as an equalizer. The reproduced sound added to this external noise is collected by the internal microphone unit 6. The internal microphone unit 6 inverts the phase of the collected reproduced sound and supplies it to the adder 9.

The adder 9 adds the phase-inverted signal supplied from the internal microphone unit 6 and the output signal from the equalizer 8. Thereby, the sound emitted from the earphone unit 3 can be made into clear reproduced sound with external noise removed.

This reproduced audio is output via the output terminal P. That is, the signal level supplied from the input terminal 7 is S, and the transfer function of the internal microphone unit 6 is M. Control circuit 1
The transfer function of amplifier 11 is β, and the transfer function of amplifier 11 is A. The transfer function of the earphone unit 3 is expressed as H. When the external noise level supplied from the input terminal 13 is N and the reproduced sound level output from the output terminal 14 is P, the reproduced sound level P is expressed as follows. Note that each of the above transfer functions M, β, A, and H is expressed in the frequency domain. At this time, AHMβ》
If it is 1, the reproduced audio level P is 1 P=S+NAHMβ. From now on, if the condition of AHMβ》1 is satisfied, the reproduced audio level P will be determined by the transfer function A of the amplifier 11. It can be seen that this is not affected by the transfer function H of the earphone unit 3. Therefore, by varying the gain of the amplifier l1 under conditions that satisfy AHMβ》l, it is possible to vary the level of external noise that is negatively fed back by the internal microphone unit 6, regardless of the level of the reproduced sound. For example, when the external noise is large, the gain of the amplifier 11 is increased to increase the amount of noise reduction, and conversely, when the external noise is low, the gain of the amplifier 11 is increased.
By reducing the gain of l, the above-mentioned intrahead localization phenomenon can be effectively prevented and the reproduced sound can be heard clearly. Figure 3 is a diagram showing the external appearance of a so-called head nodescent device in which such a noise reduction device is applied. In FIG. 3, the acoustic tubes 1.1 are bent within a range that does not affect the acoustic impedance, and the two acoustic tubes 1.1 are connected by the connecting member 15 so that each mounting member 4 faces the earpiece. For example, an end of the bar 21 is attached to the connecting member 15, etc., and a transmitting microphone is attached to the other end of the bar 21. Then, these two acoustic tubes 1.1 are passed around the head as a hair band, and the attachment member 4 of the acoustic tube 1 is
If the mounting member 4 is opened slightly and attached to the auricle D, the mounting member 4 will be pressed against the entrance of the external auditory canal A from both sides without putting pressure on it, and the mounting member 4 will be attached to the auricle D. It can be prevented from coming off from D, allowing for good attachment and clear communication.

As is clear from the above description, since the noise reduction device according to the present invention uses the above-mentioned acoustic tube l, there is no reflection of sound within the tube and no intrahead localization phenomenon occurs, and external noise is effectively reduced. It is possible to achieve a smaller size and lighter weight. Therefore, the sound can be heard clearly even if the volume is not played at high volume, and the sound that is being heard will not be leaked to those around you. Note that the negative feedback loop described above can also reduce distortion of the earphone unit.

Furthermore, when used as a headphone set, for example, there is no need to cover the ears with a headphone cup or the like and put pressure on them, so fatigue caused by wearing the headphones for a long time can be reduced.

Note that the noise reduction device according to the present invention is not limited to the above-mentioned embodiments, and may of course be used for earphone devices such as small portable headphone players, handsets of telephones, etc. It is. [Effects of the Invention] The noise reduction device according to the present invention includes an acoustic tube formed to have an inner diameter substantially the same as that of the external auditory canal, one end of which is an auricle attachment portion, and the other end of which is a non-reflection end for sound; and an earphone unit and an internal microphone unit, each of which is provided near the ear, and which are mounted close to each other on the circumferential surface of the acoustic tube with each imaging surface facing inward of the tube, and the internal microphone unit By inverting the phase of the external noise in the acoustic tube that is picked up by the notebook and producing sound through the earphone unit, external noise can be effectively reduced and good reproduced sound can be heard.

[Brief explanation of drawings]

Fig. 1 is a sectional view of the noise reduction device according to the present invention, Fig. 2 is a block diagram of the noise reduction device according to the embodiment, and Fig. 3 is an external appearance when the noise reduction device 1 according to the present invention is applied to a hesodoset. This is a diagram showing l・・・・・・・・・Acoustic tube 3・・・・・・・・・Earphone Uninote 4・・・
......Mounting member 5...Sound absorbing material 6...Internal microphone unit 7
, l3... Input terminal 8... Equalizer 9.12...
......Adder 10......Control circuit 11...
...... Amplifier 14 ...... Output terminal

Claims (1)

[Scope of Claims] An acoustic tube formed to have approximately the same inner diameter as the external auditory canal, with one end serving as an auricle attachment part and the other end serving as a non-reflecting end for sound; and an acoustic tube provided near the ear when worn. and an earphone unit and an internal microphone unit that are mounted close to each other on the circumferential surface of the acoustic tube with their respective vibration surfaces facing inward of the tube, and the external noise inside the acoustic tube that is collected by the internal microphone unit is A noise reduction device characterized by reducing external noise by inverting the phase of and producing sound through the earphone unit.