JP2009219095A - Sound insulating element for inner earphone, inner earphone, and sound reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inner earphone which attains noise reduction so that it can be used even in a subway train of 80 to 90 dB noise environment, and yet has merits of high performance, high stability, simplicity, and low cost. <P>SOLUTION: High-level ambient noises that pass through an inner earphone can be insulated by filling the space between the ear and the inner earphone with a sound insulating element which consists of porous soft plastics. The reproducing sound which is strongly attenuated by the sound insulating element is corrected in advance by signal processing to secure sound quality. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

Definition of terms

Throughout the entire sentence including the claims, the description in {} in the sentence takes precedence over the description outside {}.

Environmental noise canceller, environmental noise reduction, earphone manufacturing technology, earplug material processing technology, electronic circuit filter, digital signal processor signal processing algorithm.

Earphones and handsets with functions that reduce environmental noise and make it easier to listen to music and speech are on the market. Broadly divided into an active method and a passive method.

As background technology of the active method,
{Because it is necessary to incorporate a microphone in the immediate vicinity of the earphone} Advanced {design and manufacturing} technology is required.
Technology that avoids operational instability when trying to improve cancellation performance even in higher frequency ranges.
A method for reducing unpleasant noise caused by {friction and static electricity discharge} generated between the earphone cord and clothes.
In a noise environment exceeding 85 dB, such as in a subway train, avoidance of the phenomenon of significant deterioration in cancellation performance due to the non-linear characteristics of {acoustic propagation system, microphone, earphone, headphone}, etc.
Reduction of current consumption is an important factor for portable devices to achieve higher performance.

Many patent applications have been filed for active noise cancellers.
The following are typical examples.
Japanese Patent Application Laid-Open No. 2001-5463 Sound Device Japanese Patent Application Laid-Open No. H7-264699 Hearing Aid Japanese Patent Application Laid-Open No. H9-36763 Noise Canceller Japanese Patent Application Laid-Open No. 2006-139307 Japanese Patent Application Laid-Open No. H-303051 Open H8-47074 Supra Oral Headphone Japanese Unexamined Patent Publication H8-79873 Communication Terminal Japanese Unexamined Patent Publication H8-275281 Noise Canceling Headphone Japanese Unexamined Patent Publication H11-308685 Active Noise Reduction Headset Japanese Unexamined Patent Publication 2000-59876 Acoustic Device and Headphone Japanese Unexamined Patent Publication H6-6886 Noise Reduction Headphone Japanese Patent Laid-Open No. H6-70391 Headphone Device Japanese Patent Laid-Open No. H7-240989 Noise Reduction Headphone Device

As background technology of passive method,
To block the sound propagation path from the environmental noise source to the hearing,
A technique that improves the external noise blocking performance of the earphone itself while maintaining the playback performance of the earphone.
Improvement of the sound insulation element material and shape to improve the sound insulation performance of the gap between the ear and the earphone.
The above two points are important.
Japanese Patent Application Laid-Open No. H08-275298 Earplug Earphone Headphone and Headphone Japanese Patent Application Laid-Open No. H10-511832 Headset with ear cushion and device for limiting the compression of the cushion have been proposed. As a result of propagating through this structure, it is possible to reach hearing, and high satisfaction with respect to noise reduction performance has not been obtained.

In Japanese Patent Laid-Open No. 2002-200109 earplug type electroacoustic transducer, there is a proposal for functioning noise reduction by directly transmitting {vibration of an earphone diaphragm} to a {sound insulation element which is an earplug}. It is a material unsuitable for {propagating sound directly from a material with completely different propagation characteristics by mechanical vibration}, and it is difficult to obtain good acoustic performance.

Problems to be solved by the invention

Noise reduction that is practical, inexpensive, easy to manufacture, easy to use, with high reduction performance and good playback sound quality.

In general, in order to improve the reproduction performance of the earphone, it is convenient that {the rear surface of the diaphragm} is opened outward. However, in the conventional method of {blocking environmental noise}, regardless of {active type or passive type}, {the purpose of blocking environmental noise} is because the back of the diaphragm of the earphone is sealed. } Is desirable. Although it is easy to seal the back of the earphone, the playback performance is significantly deteriorated by sealing. In particular, in order to avoid low sound reproduction performance {remarkable deterioration due to sealing}, there is a product that has been finely crafted, such as providing a duct from the back of the diaphragm and opening it to the opposite ear side. In short, {improvement in sound insulation performance of the earphone itself} and {improvement in reproduction performance of the earphone} are generally incompatible with each other.

It is necessary to incorporate a microphone into an active noise canceller type earphone. It is not easy to place a microphone in a small, complex and precise earphone, and unfortunately, the more accurate the detection performance is, the closer the earphone and the microphone are. However, on the other hand, since the degree of coupling with the earphone increases, the magnitude of the environmental noise to be detected becomes relatively small and control becomes difficult. In this respect as well, a compromise between conflicting issues must be sought.
Furthermore, the provision of a microphone tends to pick up unpleasant noise due to {friction noise and generated electrostatic discharge} with the cord clothes.

The active noise canceller type earphone has {closed loop of signal flow} from {microphone for detecting environmental noise} to amplifier through the amplifier, signal processing and reproduction system, and {improvement of sound insulation performance} { Increase in instability}, and in this respect as well, a compromise with conflicting issues must be sought.

In addition, when the signal processing is digital signal processing (the high-performance type is this case), {the time delay required for AD conversion and DA conversion} determines the performance limit, so {high cost, high speed, low noise AD, DA conversion method} must be used.

Means for solving the problem

{Enclose the space between the inner earphone and hearing (a part of the external auditory canal through which sound is transmitted)} with a sound insulation element that attenuates the sound, so that {the environmental noise you want to reduce} and {the music or announcement signal you want to hear} Attenuate both. Since this method {insulates the reproduced sound with a material having a high performance sound insulation effect}, the volume of the reproduced sound is attenuated, and the attenuation is particularly large as the sound is high. As for this attenuation, at the stage of the electric signal, the {reverse transmission characteristic of the attenuation characteristic of the sound insulation element from the inner earphone to the auditory sense} is applied to correct the reproduction signal and drive the inner earphone. Since the environmental noise intruding from the gap between the earphone and the ear is also cut off in the same way, the noise insulation of the environmental noise is greatly improved, and consideration is given to {the sound insulation effect of the earphone itself} Is greatly reduced, and the degree of freedom in designing the {earphone itself or the sound insulation element} is dramatically increased.

As a result, the sound insulation performance of environmental noise is improved, {attenuation of reproduced sound} is corrected to normal sound quality, and the S / N ratio is improved.

FIG. 1 is a diagram showing an embodiment of the present invention.
1 is an earphone main body, 2 is environmental noise, 3 is friction noise, 4 is a reproduction signal of the earphone, 5 is {environmental noise and friction noise} through the earphone main body, and 6 is {soft soft sound insulation described later] A hollow sound insulation performance stabilizing tube 7 for facilitating mounting of the element on the earphone body and stabilizing the sound insulation performance of the sound insulation material (in use) 7 is one of the spaces formed between the earphone body and the ear canal A sound insulating element 8 made of {a deformable, sound insulating porous plastic material} for closing the portion, and 8 is a space formed inside the sound insulating element. The material of the sound insulation performance stabilizing tube 6 is softer than the material of the sound outlet of the earphone and is harder than the sound insulation material, and it is desirable that it can be easily and stably attached to the earphone.
Details of {material and shape of sound insulation element} and {material and shape of sound insulation performance stabilizing tube} are not the essence of the present invention, and thus the description thereof is omitted.

FIG. 2 is a view showing a state where the embodiment of FIG. 1 is worn on the ear.
1 to 8 are the same as those in FIG. 9 is the contour of the ear canal, 10 is the ear canal, 11 is a reproduction signal of the earphone that reaches the hearing through the sound insulation element, and 12 is the noise that reaches the hearing through the sound insulation element.

The {reproduced sound 4 of the earphone 4} and the {environmental noise and frictional noise 5 entering through the earphone} are attenuated by the sound insulation effect of the sound insulation element 7 and reach the hearing through the ear canal. As is clear from the figure, since a part of the ear canal is blocked by the sound insulation element, environmental noise and frictional sound reaching the hearing are greatly attenuated by the {sound insulation effect of the sound insulation element}. Naturally, the reproduced sound of the earphone is also attenuated in the same manner. However, the {reproduced sound of the earphone} is {insulated by applying {inverse characteristics of the attenuation effect by the sound insulation element} in advance by {signal processing of the electronic circuit}. Attenuation by element} can be corrected. As a result, the original reproduced sound can be reproduced with {almost the same volume and sound quality as in the case where no sound insulation element is provided}, so {environmental noise and chord friction sound} is {the amount of sound insulation effect of the sound insulation element}. Only reduced. The sound insulation performance stabilizing tube 6 stabilizes {the shape of the sound outlet of the earphone}, that is, {stablely secure the space 8}, so that the {the sound insulation element is attached to the ear} It has a role of {securing stable sound insulation performance}. In many experiments, the sound insulation performance is greatly affected by the {volume of the portion where the sound insulation element blocks the ear canal} and {the shape of the space 8 inside the sound insulation element} with the earphone inserted into the ear. The role of the stabilizing tube is great.

FIG. 3 is a diagram showing an embodiment of the present invention.
The same number as FIG. 1 is the same function. 3 is different from FIG. 1 in that FIG. 1 does not penetrate the sound insulation element 7 but penetrates the sound insulation element of FIG.

FIG. 4 is a diagram showing a state in which the embodiment of FIG. 3 is inserted into the ear.
1 to 12 are the same as those in FIG. The difference between FIG. 4 and FIG. 2 is that the hole of the sound insulation element penetrating in FIG. 3 is {the sound insulation element through hole} is {soft sound insulation material} on the wall of the ear canal when the earphone is inserted into the ear. It is pressed and closed, and is functionally the same as FIG.

FIG. 5 is a diagram showing an example of a conventional noise canceling earphone.
The same number as FIG. 1 is the same function. The sound insulation element penetrates, and the reproduced sound of the earphone reaches the hearing as it is.

FIG. 6 is a diagram showing a state in which the conventional example of FIG. 5 is inserted into the ear.
The playback signal of the earphone reaches the hearing through the ear canal as it is without sound insulation. Naturally, the {environmental noise and frictional noise of the cord} transmitted through the earphone itself reaches the auditory sense without being shielded, so the performance of blocking the {environmental noise and frictional noise} of the earphone itself must be high. .

[FIG. 7] uses {the sound insulation element of one sample in the embodiment of FIG. 2, {reproduced sound in the state of wearing on the ear}} and the same earphone, and {the conventional example of FIG. In FIG. 2, {a sound insulation element of one sample} is used to compare both {reproduced sound worn in the ear}}, and {input level of the embodiment of FIG. 2} is set so that both have equal volume. By adjusting, {the sound insulation characteristic of the sound insulation element in the state inserted in the ear of FIG. 2} is equivalently measured. The signal used for the measurement is a sine wave.

The horizontal axis of the graph corresponds to a piano keyboard, {the leftmost side of the horizontal axis is 43.8 Hz E}, and {the rightmost side is 16572 Hz E}. One scale on the horizontal axis is the chromatic scale. The vertical axis represents {attenuation amount of sound insulation element}. Graph 1 is obtained by calculating {equivalent volume for each chromatic scale}, converting it into attenuation, and plotting it, and it is 0 dB on the basis of {43.8 HZ E equal volume level}. Since this data is a sample and is a comparative measurement in human hearing, it contains subjective errors. In addition, although there is a difference in characteristics depending on the sample, it generally has an attenuation characteristic that falls to the right. {Line 2 in FIG. 7} is a characteristic obtained by roughly linearly approximating the measurement result of graph 1. The fact that {attenuation characteristics of 1 or 2 in FIG. 7} can be approximately corrected by using a {filter having a simple configuration using an electronic circuit} is not the essence of the present invention, and thus the description thereof is omitted.

By correcting the reproduction signal in advance with the inverse characteristic of {attenuation characteristic shown in FIG. 7}, the {reproduction signal passing through the sound insulation element in FIG. 2} becomes {reproduced sound substantially the same as the reproduction signal in FIG. 6}. To reach. {Environmental noise and friction noise} are reduced by the attenuation characteristics shown in FIG.
However, since the reverse attenuation characteristic of this attenuation characteristic requires a gain of 30 dB in the high sound range, {the corresponding decrease in dynamic range} is a negative element of the present invention.
However, the fact that there is no practical problem will be described below using actually measured data.

[FIG. 8] is a peak hold distribution of a spectrum of an example of music containing female vocals.
[FIG. 9] is a peak hold distribution of a spectrum of an example of music containing male vocals.
[FIG. 10] is a peak hold distribution of a spectrum of an example of movie music.
[FIG. 11] is a peak hold distribution of the spectrum of the jazz music example.
[FIG. 12] is a peak hold distribution of a spectrum of an example of music by an orchestra.
[FIG. 13] is a peak hold distribution of a spectrum of an example of music by a choir.
[FIG. 14] is a peak hold distribution of a spectrum of a strong bass musical example.
[FIG. 15] is a peak hold distribution of a spectrum of a pleasant musical example.
[FIG. 16] is a peak hold distribution of the spectrum of news alternating between male and female.
[FIG. 17] is a peak hold distribution of the spectrum of the male lecture.
[FIG. 18] is a peak hold distribution of the spectrum of the jet engine sound.
[FIG. 19] is a peak hold distribution of a lightning sound spectrum.

The spectral density in the vicinity of 10 kHz of any of the signals shown in FIGS. 8 to 19 is approximately 30 to 40 dB lower than the mid-low range. Therefore, it can be seen that there is no problem with the dynamic range as a whole even if the correction is performed up to about 30 dB in the high sound range.
On the other hand, since the product on the market {has a dynamic range that can be heard even in considerable environmental noise}, {signal reduction to compensate for {decrease in dynamic range, which is a weak point of the present invention} There is no {need to be larger} for {dynamics of the processing unit and amplifier} for {product of the present invention}.

As explained above,
When {the sound insulation element attached to the earphone} is {a structure that blocks a part of the ear canal}, {even an earphone with a rear opening} can realize high-performance noise reduction.
Not only can environmental noise be easily reduced, but {conventional manufacturing technology and equipment} is inexpensive, stable, and has good sound quality with low distortion and electronic circuit noise.
Since {earphones themselves} and {sound insulation elements} are low-cost, they can be easily replaced even when they are damaged or lost or the sound insulation elements are replaced.
{No device for AD / DA conversion with extremely small delay time} for improving performance is not required.
{Where the stability of closed loop including complex filters} or {problems where control performance is significantly degraded by nonlinear characteristics existing in the system}, etc. {need to find a compromise between conflicting problems} No difficult signal processing techniques} are required.

The invention's effect

{Easy, high performance, low cost} {reproduction environment with environmental noise reduction function} can be provided, so it can be applied to a wide range of products.
Even in a noisy environment, it is possible to listen to music with a {small volume on the eardrum} and {good sound quality}, and therefore it is possible to provide a safer reproduction environment even for the influence on the feared hearing impairment.
Because of the low price, the majority of people, not a part, can enjoy comfortably at {reasonable volume and good sound quality} in a boring long time in {trains and airplanes}. .
For mobile phone calls in a noisy environment, the listening conditions are much better, which not only makes usability more convenient, but also acts to reduce loud phone conversations, which are common in noisy environments. .

An earphone in which the sound insulating element of the present invention is attached to a {back-opening type most common earphone with good reproduction characteristics} provided with a structure capable of mounting the sound insulating element of the present invention.
Exchangeable sound insulation elements of various {designs and shapes}.
A combination of {an earphone equipped with the sound insulation element of the present invention} and {a music reproduction device, a mobile phone or a reproduction terminal device incorporating the reverse attenuation acoustic characteristic of the sound insulation element}.

Sound insulation element for earphones Earphone sound insulation element equipped with sound insulation element can be attached Earphone Earphones can be attached to earphones Earphones can be attached to sound insulation elements Aircraft passenger seat reproduction terminal device incorporating reverse attenuation characteristics of train Passenger seat reproduction terminal device incorporating reverse attenuation characteristics of sound insulation element

It is practical, inexpensive, easy to manufacture, easy to use, has high reduction performance, and has good reproduction sound quality. Therefore, unlike the current noise reduction method, the application range is extremely wide. The present invention has the possibility of being mounted on {almost all devices} with {possibility to listen to sound under noise}.

Illustration of one embodiment Explanatory drawing in the use condition of the Example of FIG. Illustration of one embodiment Explanatory drawing in the use condition of the Example of FIG. Illustration of a conventional example Explanatory drawing in the usage state of the conventional example Example of attenuation characteristics of sound insulation element of the present invention Spectrum peak hold distribution of female vocal music example Spectrum peak hold distribution of movie music composition example Spectrum peak hold distribution of jazz music example Spectrum peak hold distribution of musical example by orchestra Peak hold distribution of the spectrum of a sample song by a choir Spectrum peak hold distribution of strong bass example music Peak hold distribution of the spectrum of a pleasant example of music Male-female alternating news spectrum peak hold distribution Peak hold distribution of male lecture spectrum Peak hold distribution of jet engine sound spectrum Peak hold distribution of lightning sound spectrum

Claims (4)

When the inner earphone is attached to the ear, the {inner earphone and part of the vicinity of the entrance to the ear canal} space should be filled with {deformable sound-insulating porous plastic material (hereinafter referred to as sound insulating material)}. A sound insulation element made of a sound insulation material having a function of closing the space so as to attenuate both environmental noise and sound reproduced by the inner earphone. In the space inside the sound insulation element, {in order to ensure a stable sound exit space without the sound insulation material being deformed more than necessary at the sound output of the earphone with the sound insulation element attached to the ear { As an aggregate of soft sound insulation material}} or {When attaching a soft sound insulation element to the sound outlet of the earphone, in order to ensure a stable wearing state, {the sound insulation material is softer than the sound outlet on the earphone side. The sound insulation element as defined in claim 1, further comprising a sound insulation element made of a harder material. An earphone provided with the sound insulation element of {Claim 1 or Claim 2}. In an apparatus for reproducing an acoustic signal using the {inner earphone equipped with the sound insulation element according to claim 1 or claim 2 or the {inner earphone according to claim 3}}, the inner earphone is caused by the attenuation effect of the sound insulation element. A sound signal reproducing apparatus having a function of correcting in advance the attenuation characteristics generated during the process of reproducing the sound of the sound of {1} by {electronic circuit or digital signal processing}.

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