The present invention is related generally to a recording device and, more particularly, to circuit and method for noise reduction of a recording device.
Wind noise and other ambient noise are usually troublesome for a sound recording device such as a digital video camera and a recording pen. Using a specific algorithm or filter to locate the characteristics of noise and remove it from original sound requires a lot of computing power and corresponding hardware cost. Using a microphone array (two or more microphones), for example, U.S. Pat. Nos. 7,174,023 and 7,895,036 and U.S. Pat. Publication No. 2009/0002498, can achieve better results but the cost of additional microphones is still an issue.
In the field of communications, on the other hand, U.S. Pat. Publication No. 2011/0181452 teaches using a speaker at the far end that is communicating with the user of a communication device at the near end as a microphone for microphone array noise reduction of the sound transmitted to the far end. However, this art adopts a speaker as a microphone for a communication device to perform acoustic echo cancellation/suppression or level adjustment, but is not dedicated to enhance the quality of sound recording.
Therefore, it is desired circuit and method for noise reduction of a recording device without using additional microphones.
An objective of the present invention is to provide a low noise recording device and a noise reduction method thereof.
Another objective of the present invention is to provide a recording device and method using a speaker as a microphone for noise reduction.
According to the present invention, during sound recording by a microphone, a recording device and method locate characteristics of noise by using a speaker as a second microphone to simultaneously receive sound, and then use the characteristics of noise for noise reduction of the received sound by the microphone, thereby improving the quality of sound recording.
These and other objectives, features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings, in which:
Since a recording device already has a microphone for receiving sound and a speaker for playing sound, using the speaker as a second microphone to characterize noise requires no additional microphones. Specifically, using the existing speaker of a recording device as a second microphone to establish a microphone array with the existing microphone of the recording device for noise reduction of the recording device needs no costs of additional microphones.
Analog processors and digital processors for applying signal processing to sound in a recording device or a communication system are well known, for example, as mentioned in U.S. Pat. Publication No. 2011/0181452. Circuit and operation of a wind noise extractor may also refer to U.S. Pat. Nos. 7,174,023 and 7,895,036 and U.S. Pat. Publication No. 2009/0002498 for details. Thus, the circuits and operation of the analog processors 14, 16 and 42, the digital processors 32 and 38, and the wind noise extractor 26 are not described herein.
Since major energy of wind noise is located as low frequency, a speaker as a microphone is enough to characterize it, and eliminates the requirement of additional microphones. Likewise, it may also use a speaker as a microphone to pick up other acoustic or mechanical noise and reduce those noise in other applications. For example, a speaker can be adopted to receive motor noise of lens module of a digital video camera or other collision noise occurred at recording device itself.
In some applications, the equalizer 24 and the digital processors 32 and 38 shown in
While the present invention has been described in conjunction with preferred embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and scope thereof as set forth in the appended claims.
Number | Date | Country | Kind |
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101100482 | Jan 2012 | TW | national |