JP2006325895A - Noise reducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a noise reducing device capable of controlling perception of noise. <P>SOLUTION: The noise reducing device is equipped with a bone conduction microphones 21 for detecting a bone conduction sound transmitted from a noise source through a human body, a bone conduction speakers 22 for transmitting a bone conduction interference sound to the human body, and a control means 2 which has a digital filter 25 for converting and processing an input signal from the bone conduction microphones 21 to a signal with the same amplitude and reverse phase and generates the bone conduction interference sound based on the signal after conversion and processing. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a noise reduction device for reducing noise generated from a dental cutter or the like.

  As a device for reducing unpleasant noise generated from a dental cutter or the like, a method of reducing this cutting noise by active noise control has been conventionally known. For example, the apparatus disclosed in Patent Document 1 detects the noise of a dental cutting instrument with a sound wave detector provided in the vicinity of a patient, and generates an interference sound wave having the same amplitude and opposite phase as the detected sound wave, It is configured to reduce noise.

As described above, Patent Documents 2 and 3 disclose methods for reducing noise by sound wave interference based on detected noise.
JP-A-4-242638 Japanese Unexamined Patent Publication No. 4-266653 Japanese Utility Model Publication No. 6-75422

  However, according to the above-described conventional apparatus, although air conduction sound is reduced, noise is still perceived, so that the level of discomfort can not be sufficiently solved.

  Therefore, an object of the present invention is to provide a noise reduction device that can suppress noise perception.

  The object of the present invention is to provide a bone-conduction microphone for detecting bone-conduction sound transmitted from the noise source through the human body, a bone-conduction speaker for transmitting bone-conduction interference sound to the human body, and an input signal from the bone-conduction microphone. The present invention is achieved by a noise reduction device including a digital filter that performs conversion processing to a signal having the same amplitude and opposite phase, and control means that generates the bone-conduction interference sound based on the signal after the conversion processing.

  In this noise reduction apparatus, it is preferable that the digital filter has a filter coefficient based on a transfer function between a position where the bone-conduction microphone and the bone-conduction speaker are attached to a human body and an inner ear position.

  In addition, an air conduction microphone that detects sound waves from a noise source, an air conduction speaker that outputs air conduction interference sound as sound waves, and an input signal from the air conduction microphone are converted into signals of the same amplitude and opposite phase. It is preferable to further include a control unit that has a digital filter and generates the air conduction interference sound based on the signal after the conversion process.

  According to the noise reduction device of the present invention, noise perception can be suppressed.

Hereinafter, actual forms of the present invention will be described with reference to the accompanying drawings. FIG. 1 is an overall configuration diagram of a noise reduction apparatus according to an embodiment of the present invention, and shows a state where the apparatus is installed in a treatment chair 50 such as a dental clinic from above.

  As shown in FIG. 1, the noise reduction device 1 includes an air conduction sound suppression unit 10 and a bone conduction sound suppression unit 20.

  The air conduction sound suppression unit 10 includes an air conduction microphone 11 provided at the upper center of the backrest part 51 of the treatment chair 50 and air conduction speakers 12 and 12 provided on the left and right sides of the backrest part 51. These are connected to the control device 2. The bone conduction sound suppression unit 20 includes a bone conduction microphone 21 that detects bone conduction sound transmitted from the noise source through the human body and a bone conduction speaker 22 that transmits bone conduction sound to the human body. Respectively attached to the vicinity of the left and right milky protrusions on the head 61 of the 60. The bone conduction microphone 21 and the bone conduction speaker 22 are connected to the control device 2.

  The configuration of the air conduction sound suppression unit 10 is shown in a block diagram in FIG. The air conduction noise input to the air conduction microphone 11 from a noise source such as a cutting tool is amplified by the microphone amplifier 13 and input to the digital filter 15 via the A / D converter 14. The digital filter 15 converts the input signal into a signal having the same amplitude and opposite phase and outputs the signal. This output signal is amplified by the power amplifier 17 via the D / A converter 16 and then output as air conduction interference sound from the air conduction speakers 12 and 12 to both ears of the patient 60. Thus, the sound wave generated from the noise source interferes with the air conduction interference sound generated by the air conduction sound suppression unit 10 at the binaural positions 62 and 62 of the patient 60, and the transmission to the patient 60 as the air conduction sound is suppressed. Is done. The number and arrangement of the air conduction microphones 11 and the air conduction speakers 12 are not limited to those of the present embodiment.

  Next, the configuration of the bone conduction sound suppressing unit 20 is shown in a block diagram in FIG. The bone conduction noise inputted from the bone conduction microphone 21 is amplified by the microphone amplifier 23 and inputted to the digital filter 25 through the A / D converter 24. The digital filter 25 converts the input signal into a signal having the same amplitude and opposite phase and outputs the signal. This output signal is amplified by the power amplifier 27 through the D / A converter 26 and then output from the bone conduction speaker 22 as bone conduction interference sound. A plurality of bone conduction sound suppression units 20 are provided corresponding to both ears.

  The present inventors have revealed that during dental treatment, not only noise such as a cutting turbine is perceived by the patient as air conduction sound, but also that cutting vibration from the cutting tool is perceived by the patient as bone conduction sound. did. According to the noise reduction device 1 of the present embodiment, by providing the bone conduction sound suppression unit 20, the bone conduction noise can be made to interfere with the bone conduction interference sound, and the transmission of the bone conduction sound to the patient 60 is suppressed. be able to.

  Since the bone conduction sound is perceived by the inner ear through the skull or the like, it is preferable to control the bone conduction interference sound to have the same amplitude and opposite phase with respect to the bone conduction noise at the position of the inner ear of the patient 60. That is, the filter coefficient in the digital filter 25 is set in consideration of the transfer function F between the bone conduction microphone 21 and the bone conduction speaker 22 attached to the human body (in this embodiment, the mastoid process) and the inner ear. It is preferable. The transfer function F can be estimated by analyzing the bone conduction sound propagation process in the head by computer simulation.

Specifically, first, a human head model is created with reference to a standard Japanese male head anatomy, and a vibrator is placed at a desired position on the xy plane including the cochlea. And the time domain finite difference method (FDTD method: Finite- Difference Time-Domain Method) used for the sound field analysis in the fluid
), The transfer function F can be obtained by calculating the sound pressure distribution formed in the head by the vibrator. An example of the transfer function F between the mastoid process and the cochlea is shown in FIG.

  FIG. 5 is a cross-sectional view of the bone-conduction microphone 21. The bone conduction microphone 21 includes a cylindrical case 32 in which a detector 31 for detecting bone conduction sound is accommodated, and a suction cup 34 is attached to the opening edge of the case 32.

  The detector 31 is supported by a gimbal mechanism so as to be swingable about two axes orthogonal to each other. That is, the detector 31 is fixed to the first frame body 40 so as to expose the pickup portion, and the first frame body 40 is attached to the second frame body 44 via the first support shaft 42. It is swingably supported. The second frame body 44 is swingably supported inside the case 32 via a second support shaft 46 orthogonal to the first support shaft 42. The pickup portion of the detector 31 slightly protrudes from the opening of the case 32, and is configured such that when the suction cup 34 is adsorbed to a predetermined attachment site, the pickup portion comes into contact with and presses the surface to be adsorbed. A communication hole 32a is formed at the center of the bottom (upper part of the figure) of each case 32, and a spherical bag-like body 48 is coupled to the communication hole 32a. The bag-like body 48 is made of an elastic material such as a rubber material, and is configured to be elastically deformable by pressing. The internal space of the bag-like body 48 communicates with the inside of the case 32 through the communication hole 32a.

  The bone-conduction speaker 22 is configured in the same manner as the bone-conduction microphone 21 except that a transducer for transmitting mechanical vibration to the human body is provided instead of the detector 31 in the configuration of the bone-conduction microphone 21 described above. Yes.

  According to the bone-conduction microphone 21 and the bone-conduction speaker 22 configured as described above, even if the surface is attached to a part having a complicated three-dimensional shape such as a milky process, the positional deviation and posture with time Therefore, it is possible to reliably detect bone conduction noise and output bone conduction interference sound.

  The bone-conducting microphone 21 and the bone-conducting speaker 22 are preferably attached to a position close to the auditory receptor such as the sternocleidomastoid muscle and the back of the cheekbone in addition to the mastoid process. The position is not particularly limited as long as the bone conduction sound can be detected and transmitted, and the bone conduction noise can be reduced by considering the transfer function of the bone conduction sound between the attachment position and the inner ear. In the present embodiment, a plurality of bone-conducting microphones 21 and bone-conducting speakers 22 are provided corresponding to both ears, but may be single.

  As mentioned above, although one Embodiment of this invention was described, the specific aspect of this invention is not limited to the said embodiment. For example, in the present embodiment, the air conduction sound suppression unit 10 and the bone conduction sound suppression unit 20 are provided to suppress both the air conduction sound and the bone conduction sound emitted from the cutting tool. Since the noise reduction effect can be expected with the earplugs or the like for the sound guide, a configuration including only the bone-conduction sound suppressing unit 20 may be used.

  The noise suppression device of the present embodiment is mainly intended to reduce cutting noise during dental treatment, but is not limited to this application. In addition, bone conduction such as underwater construction work and dismantling work is performed. This is particularly effective in cases where noise is a problem.

1 is an overall configuration diagram of a noise suppression device according to an embodiment of the present invention. It is a block diagram of the air conduction sound suppression part in the noise suppression apparatus shown in FIG. It is a block diagram of the bone conduction sound suppression part in the noise suppression apparatus shown in FIG. It is a figure which shows an example of the estimation result of a transfer function. It is sectional drawing of the bone-conduction microphone in the bone-conduction sound suppression part shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Noise suppression apparatus 2 Control apparatus 10 Air conduction sound suppression part 11 Air conduction microphone 12 Air conduction speaker 15 Digital filter 20 Bone conduction sound suppression part 21 Bone conduction microphone 22 Bone conduction speaker 25 Digital filter

Claims (3)

A bone-conduction microphone that detects bone-conduction sound transmitted through the human body from a noise source;
A bone-conducting speaker that transmits bone-conduction interference to the human body;
Noise reduction comprising: a digital filter that converts an input signal from the bone-conduction microphone into a signal having the same amplitude and an opposite phase, and generating the bone-conduction interference sound based on the signal after the conversion process apparatus. The noise reduction device according to claim 1, wherein the digital filter has a filter coefficient based on a transfer function between a position where the bone-conduction microphone and the bone-conduction speaker are attached to a human body and a position of the inner ear. An air conduction microphone that detects sound waves from a noise source;
An air conduction speaker for outputting air conduction interference sound as a sound wave;
And a control unit that includes a digital filter that converts an input signal from the air conduction microphone into a signal having the same amplitude and an opposite phase, and that generates the air conduction interference sound based on the signal after the conversion process. Item 3. The noise reduction device according to Item 1 or 2.