JP4900740B2 - Noise reduction device - Google Patents

Description

  The present invention relates to a noise mitigation device for mitigating 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, the conventional apparatus described above requires detailed analysis of the sound field propagation process in the target space, and it is difficult to control in a complex space such as the inside of the human head. In particular, high-frequency sound has a risk of increasing noise. As a result, the current situation is that noise cannot be alleviated and the level of discomfort can not be sufficiently resolved.

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

  The object of the present invention is achieved by a noise mitigation device comprising a bone conduction speaker for transmitting bone conduction sound and bone conduction sound masking means for generating bone conduction masking sound and outputting it from the bone conduction speaker.

  In this noise reduction apparatus, it is preferable that the frequency band of the bone conduction masking sound output from the bone conduction speaker includes at least 20 to 80 kHz.

  The bone conduction sound masking means further includes a bone conduction microphone for detecting bone conduction sound transmitted through the human body, so that the bone conduction sound masking means perceives a bone conduction sound perceived by a user based on an input signal from the bone conduction microphone. The bone conduction masking sound can be generated so that the bone conduction masking sound in the frequency band including the estimated frequency band of the bone conduction sound is perceived.

Further, the air conduction microphone for detecting gas conduction speech, by modulating a carrier signal based on an input signal from the air conduction microphone, the bone-conduction external sound generating means for generating a Honeshirubegai Buon, the bone conductive It is preferable to further include output switching means capable of switching the output from the speaker from the bone conduction masking sound to the bone conduction external sound.

  Moreover, it is preferable to further include an air conduction speaker that outputs an air conduction sound and an air conduction sound masking unit that generates an air conduction masking sound and outputs the air conduction masking sound.

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

1 is an overall configuration diagram of a noise reduction apparatus according to an embodiment of the present invention. It is sectional drawing of the bone-conduction speaker shown in FIG. It is a block diagram of the noise mitigation device shown in FIG. It is a figure which shows an example of the frequency characteristic of a bone-conduction sound. Is a diagram showing an example of frequency characteristics of the air conduction speech. It is a figure which shows an example of the transfer function between a mastoid process and a cochlea.

  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 mitigation 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 mitigation device 1 includes an air conduction noise suppression unit 10, a bone conduction noise suppression unit 20, and an external sound transmission unit 30.

  The air conduction noise suppression unit 10 includes a plurality of air conduction speakers 12 and 12 that output air conduction sound, and the air conduction speakers 12 and 12 are provided on the back surface of the backrest part 51 of the treatment chair 50. 2 is connected. On / off control of output from the air conduction speakers 12, 12, volume adjustment, and the like can be performed by operating the input device 52 installed in the treatment chair 50. In the present embodiment, the air conduction speakers 12 and 12 have earphone shapes that can be inserted into both ears 62 and 62 of the user. For example, the air conduction speakers 12 and 12 are fixed to the left and right sides of the backrest 51 of the treatment chair 50. Also good.

  The bone conduction noise suppression unit 20 includes bone conduction speakers 21 and 21 that transmit bone conduction sound to the human body, and bone conduction microphones 22 and 22 that detect bone conduction sound transmitted through the human body. The bone-conducting speakers 21 and 21 and the bone-conducting microphones 22 and 22 are both configured to be attachable to a predetermined position of the human body (in this embodiment, left and right mastoid protrusions), and are connected to the control device 2 described above. ing. Adjustment of output from the bone-conducting speakers 21 and 21 can also be performed by operating the input device 52 described above.

  FIG. 2 is a cross-sectional view of the bone conduction speaker 21. The bone conduction speaker 21 includes a cylindrical case 32 in which a vibrator 31 for transmitting bone conduction sound is accommodated, and a suction cup 34 is attached to the opening edge of the case 32.

The vibrator 31 is supported by a gimbal mechanism so as to be swingable about two axes orthogonal to each other. That is, the vibrator 31 is fixed to the first frame body 40 so as to expose the pickup portion, and the first frame body 40 is connected 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 vibrating portion of the vibrator 31 slightly protrudes from the opening of the case 32, and is configured such that when the suction cup 34 is attracted to a predetermined attachment site, the vibrating portion comes into contact with and presses the attracted surface. 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 48 communicates with the inside of the case 32 through the communication hole 32a.

  The bone-conduction microphone 22 is configured in the same manner as the bone-conduction speaker 21 except that the detector 31 is provided instead of the vibrator 31 in the configuration of the bone-conduction speaker 21 described above.

  According to the bone-conducting speaker 21 and the bone-conducting microphone 22 configured as described above, for example, even when the surface is attached to a part having a complicated three-dimensional shape such as a milky process, the positional displacement and posture with time. Can be prevented, and bone conduction sound can be transmitted and detected reliably.

  The bone-conducting speaker 21 and the bone-conducting microphone 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. There is no particular limitation as long as it is a position where transmission and detection of bone conduction sound is possible. In the present embodiment, a plurality of bone-conducting speakers 21 and bone-conducting microphones 22 are provided corresponding to both ears, but may be single.

  The external sound transmission unit 110 includes an air conduction microphone 111 that is provided in the upper center of the backrest portion 51 of the treatment chair 50 and detects air conduction sound. The air conduction microphone 111 is connected to the control device 2 described above. ing.

  The configuration of the air conduction noise suppression unit 10, the bone conduction noise suppression unit 20, and the external sound transmission unit 110 is shown in a block diagram in FIG.

  The air conduction noise suppression unit 10 generates an air conduction masking sound and outputs the air conduction sound masking unit 14 output from the air conduction speakers 12 and 12 via a D / A converter and a power amplifier (both not shown). In the control device 2. The air conduction masking sound is for masking the air conduction noise generated from a dental cutter, etc., and in this embodiment, a preset sound such as white noise or music is used. The masking unit 14 may analyze the frequency of the air conduction noise input from the air conduction microphone 111 to generate an air conduction masking sound that covers the peak frequency. An input device 52 is connected to the air conduction sound masking unit 14.

  The bone conduction noise suppression unit 20 includes a bone conduction sound masking unit 24 that generates bone conduction masking sound and outputs the bone conduction masking sound from the bone conduction speakers 21 and 21 in the control device 2. The bone conduction masking sound is for masking the bone conduction noise transmitted from the dental cutter or the like to the inner ear via the skull or soft tissue.

  The bone conduction noise input from the bone conduction microphones 22 and 22 is converted into a digital signal through an amplifier and an A / D converter (both not shown), and then input to the bone conduction sound masking unit 24. The bone conduction sound masking unit 24 performs spectrum analysis based on the input bone conduction noise, and generates a bone conduction masking sound including a frequency band covering the frequency band of the bone conduction noise. The generated bone conduction masking sound is input to the output switching unit 26, passes through a D / A converter and a power amplifier (both not shown), and bone conduction speakers 21, 22 corresponding to the bone conduction microphones 22 and 22, respectively. 21 respectively.

  In the present embodiment, as described above, the bone conduction masking sound is generated based on the input signals of the bone conduction microphones 22 and 22, but the bone conduction masking sound in a preset frequency band is output. And bone conduction noise can be masked.

As an example of the frequency characteristics of bone conduction noise, bone conduction microphones 22 and 22 are respectively attached to the left and right mastoids, and bones measured at the time of non-cutting (background noise) and at the time of cutting of the maxillary left second molar, respectively. FIG. 4 shows the frequency characteristics of the sound guide. The bone conduction microphones 22 and 22 were analyzed by fast Fourier transform (FFT) using an acceleration pickup (model number: NP3211) manufactured by Ono Sokki Co., Ltd. Further, for comparison with this, under the same conditions, the frequency characteristics of the air conduction speech measured by the microphone respectively on the right and left ear of, shown in FIG.

  4 and 5, both the bone conduction sound and the air conduction sound are detected to have a large level at the time of cutting. In particular, in the case of the bone conduction sound, a high-frequency peak component of 20 kHz or more is significantly detected. Yes. In the case of bone-conducted sound, unlike air-conducted sound, it is perceived even in a frequency band exceeding the audible range, and thus such high-frequency component masking is required.

  When the present inventors examined the frequency characteristics of the bone conduction sound at the time of cutting under various conditions, similar to the results shown in FIG. 4, the high frequency of 20 kHz or higher is used regardless of the cutting tool, cutting position, subject, and the like. It was confirmed that a peak was detected in the frequency band. Therefore, the bone conduction sound by the bone conduction microphones 22 and 22 is set by setting the frequency band of the bone conduction masking sound so that the frequency band in which the peak value of the bone conduction noise shown in FIG. Therefore, it is possible to simply mask bone conduction noise without detecting the above. Specifically, the frequency band of the bone conduction masking sound output from the bone conduction speaker 22 preferably includes 20 to 80 kHz, more preferably includes 0.125 to 80 kHz, and includes 0.125 to 100 kHz. Is more preferable. As described above, whether the bone conduction masking sound is generated based on the input signals of the bone conduction microphones 22 or 22 or based on a preset one is determined by the user by operating the input device 52. It is also possible to configure so that it can be selected.

  On the other hand, in this embodiment, when it is desired to more effectively mask the bone conduction noise by the bone conduction masking sound, the bone conduction noise is caused by the bone conduction masking sound at the inner ear position of the patient 60 where the bone conduction sound is detected. Considering the transfer function F of the bone conduction sound between the wearing position of the bone conduction speaker 21 or the bone conduction microphone 22 (left and right mastoid processes in this embodiment) and the position of the inner ear so as to be accurately masked preferable. That is, the bone conduction sound masking unit 24 estimates the frequency characteristics of the bone conduction noise at the inner ear position from the input signals of the bone conduction microphones 22 and 22 in consideration of the transfer function F, and calculates the estimated bone conduction sound frequency band. The bone conduction masking sound is generated so that the bone conduction masking sound in a frequency band including the perception is perceived.

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 (inner ear). Then, by calculating the sound pressure distribution formed in the head by the vibrator using the time-domain finite difference method (FDTD method) used for analyzing the sound field in the fluid. The transfer function F can be obtained. An example of the transfer function F between the mastoid process and the cochlea is shown in FIG.

In FIG. 3, the external sound transmission unit 110 includes a carrier signal generation unit 112 that generates a carrier signal and a carrier signal modulation unit 114 that modulates the carrier signal in the control device 2. An input signal from 111 is input to the carrier signal modulator 114 via an amplifier and an A / D converter (both not shown). The carrier signal modulator 114 modulates the carrier signal generated by the carrier signal generator 112 based on the signal input from the air conduction microphone 111, and the modulated signal is based on the input from the air conduction microphone 111. The sound is input to the output switching unit 26 as an external sound. The carrier signal generator 112 is connected to the input device 52, and the frequency, amplitude, and phase of the carrier signal can be adjusted by operating the input device 52. The frequency of the carrier signal is preferably 20 to 100 kHz which is an ultrasonic region, and more preferably 20 to 50 kHz so that a good sound sensing state of the bone conduction external sound can be obtained.

  The output switching unit 26 is connected to the input device 52, and by operating the input device 52, the output from the bone conduction speakers 21 and 21 is converted from the bone conduction masking sound generated by the bone conduction sound masking unit 24 to the carrier signal. The bone conduction external sound generated by the modulation unit 114 can be switched.

  According to the noise mitigation apparatus having the above configuration, air conduction is performed from the air conduction sound masking unit 14 and the bone conduction sound masking unit 24 via the air conduction speakers 12 and 12 and the bone conduction speakers 21 and 21 during dental treatment. By outputting the masking sound and the bone conduction masking sound, respectively, both the air conduction noise and the bone conduction noise can be reduced sensibly, and discomfort due to the cutting noise can be effectively reduced. In particular, bone conduction noise is transmitted at a large level as vibration due to tooth cutting, but effective masking cannot be performed by air conduction audible sound. By generating and transmitting it to the human body, the cutting noise can be effectively reduced.

  Further, by operating the output switching unit 26 by operating the input device 52, the output from the bone conduction speakers 21 and 21 can be switched from the bone conduction masking sound to the bone conduction external sound. Can be recognized as a bone conduction sound, and smooth communication can be achieved. The sound sensing state of the bone-conducted external sound can be optimized by adjusting the frequency, amplitude, and phase of the carrier signal by operating the input device 52. After the end of the communication, the output switching unit 26 can be operated to change the output from the bone conduction speakers 21 and 21 from the bone conduction external sound to the bone conduction masking sound again.

  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 mask 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. It is also effective in cases where noise is a problem.

DESCRIPTION OF SYMBOLS 1 Noise mitigation device 2 Control apparatus 10 Air conduction sound suppression part 12 Air conduction speaker 14 Air conduction sound masking part 20 Bone conduction sound suppression part 21 Bone conduction speaker 22 Bone conduction microphone 24 Bone conduction sound masking part 26 Output switching part 110 External sound Transmission unit 111 Air conduction microphone 112 Carrier signal uttering unit 114 Carrier signal suppression unit

Claims (3)

A bone conduction speaker for transmitting bone conduction sound;
Bone conduction sound masking means for generating bone conduction masking sound and outputting from the bone conduction speaker ; and
The noise reduction device , wherein a frequency band of bone conduction masking sound output from the bone conduction speaker includes at least 20 to 80 kHz . And air conduction microphone for detecting gas guiding sound,
A bone conduction external sound generating means for generating a bone conduction external sound by modulating a carrier signal based on an input signal from the air conduction microphone;
The noise mitigation device according to claim 1 , further comprising output switching means capable of switching an output from the bone conduction speaker from the bone conduction masking sound to a bone conduction external sound. An air conduction speaker for outputting air conduction sound;
Noise absorbing device according to claim 1 or 2 further comprising a air conduction sound masking means by generating the air conduction masking sound output from the air conduction speaker.

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