Muting device

• US 9,462,370 B2
• Filed: 01/31/2013
• Issued: 10/04/2016
• Est. Priority Date: 02/08/2012
• Status: Active Grant

• Current Assignee: Kyushu Institute of Technology
• Original Assignee: Kyushu Institute of Technology
• Inventors: Sato, Yasushi
• Primary Examiner(s): TON, DAVID L
• Application Number:
  US14/372,965
• Publication Number:
  US 20150003624A1
• Time in Patent Office: 1,342 Days
• Field of Search: 381/71.6, 381/71.11, 381/71.1, 381/71.2, 381/71.4, 381/71.7, 381/71.12, 381/92, 381/94.6, 381/96
• US Class Current: 1/1
• CPC Class Codes: G10K 11/17854 the filter being an adaptive filter
• CPC Class Codes: G10K 11/17857 Geometric disposition, e.g. placement of microphones
• CPC Class Codes: G10K 11/17861 using additional means for damping sound, e.g. using sound absorbing panels
• CPC Class Codes: G10K 11/17881 the reference signal being an acoustic signal, e.g. recorded with a microphone
• CPC Class Codes: G10K 2210/128 Vehicles
• CPC Class Codes: G10K 2210/3221 Headrests, seats or the like, for personal ANC systems
• CPC Class Codes: G10K 2210/3226 Sensor details, e.g. for producing a reference or error signal
• CPC Class Codes: H04R 1/028 associated with devices performing functions other than acoustics, e.g. electric candles
• CPC Class Codes: H04R 1/1083 Reduction of ambient noise active noise reduction per se G10K11/175; protective devices for the ear, e.g. providing acoustic protection A61F11/06
• CPC Class Codes: H04R 2217/03 Parametric transducers where sound is generated or captured by the acoustic demodulation of amplitude modulated ultrasonic waves
• CPC Class Codes: H04R 2410/05 Noise reduction with a separate noise microphone
• CPC Class Codes: H04R 2460/01 Hearing devices using active noise cancellation
• CPC Class Codes: H04R 2499/13 Acoustic transducers and sound field adaptation in vehicles
• CPC Class Codes: H04R 3/002 Damping circuit arrangements for transducers, e.g. motional feedback circuits
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407
• CPC Class Codes: H04R 5/023 in a chair, pillow

Abstract

In order to enable noises entering the ear from random directions to be muted without wearing headphones, this muting device is provided with: a super-directional microphone that detects noises in spot areas around the ear at pinpoints; and an ultrasonic speaker that modulates and outputs a carrier signal supplied by a transmitter according to noise signals detected by the super-directional microphone. Furthermore, an adaptive filter is provided, and the adaptive filter supplies noise signals with the opposite phase to noises detected by the super-direction microphone, and transmits an ultrasonic signal from the ultrasonic speaker toward the eardrum of a human.

Claims

1. A muting device comprising:

a super-directional microphone configured to detect an environmental noise and output a noise signal of the detected environmental noise;

an adaptive filter configured to input the noise signal outputted by the super-directional microphone and output a signal with a phase opposite to that of the noise signal; and

an ultrasonic speaker configured to modulate a carrier wave signal in an ultrasonic band with the signal with the phase opposite to that of the noise signal, outputted by the adaptive filter, and generate a modulated ultrasonic wave which can be demodulated by an eardrum, when reaching the eardrum, to an audible sound, the demodulated audible sound having the phase opposite to that of the environmental noise detected by the super-directional microphone, whereby a sound wave from which the detected environmental noise has been removed reaches the eardrum.

2. The muting device according to claim 1, wherein

the ultrasonic speaker includes:

a modulator configured to modulate the carrier wave signal in an ultrasonic band with the signal with the phase opposite to that of the noise signal, outputted by the adaptive filter; and

an actuator configured to input the modulated carrier wave signal and generate the modulated ultrasonic wave.

3. The muting device according to claim 1, further comprising:

a non-linear microphone to be placed in a vicinity of the eardrum, wherein the adaptive filter is a Least Mean Square (LMS) adaptive filter including a coefficient variable filter and a coefficient modification algorithm, and wherein

the adaptive filter is configured to input a signal of the non-linear microphone and modify a coefficient of the coefficient variable filter in accordance with a calculation result of the coefficient modification algorithm so that the signal of the non-linear microphone gets closer to zero.

4. The muting device according to claim 3, wherein

the coefficient of the coefficient variable filter of the LMS adaptive filter is set so that a transfer function of the LMS adaptive filter becomes an inverse function of a transfer function of an acoustic propagation system between the super-directional microphone and the eardrum.

5. The muting device according to claim 1, wherein the super-directional microphone is configured to pick up an audible sound at 20 kHz or less.