Electrical audio signal processing systems and devices – Acoustical noise or sound cancellation – Adjacent ear
Patent
1994-10-27
1997-12-16
Kuntz, Curtis
Electrical audio signal processing systems and devices
Acoustical noise or sound cancellation
Adjacent ear
381 94, G10K 1116
Patent
active
056994362
DESCRIPTION:
BRIEF SUMMARY
In the area of active noise cancellation headsets, the noisy environment often encountered in the link with communication systems causes lack of intelligibility on the outward communications path. Consequently another in-wire cancellation channel to enhance the intelligibility is required. This additional processing channel adds to the cost of the headset. "In-wire" cancellation refers to any of the active control approaches that performs the cancellation of noise in a manner such as that described in U.S. patent application No. 07/421,759, which is hereby incorporated by reference therein.
The instant invention contemplates the use of the headset residual microphones to pick up the user's speech for communications. It utilizes two separate noise canceling systems both having a residual microphone located at the ear to sense any noise remaining. They also use a controller which synthesizes the anti-noise signal and a headset driver to deliver the anti-noise signal to the ear vicinity. The algorithm used is the one described in U.S. Pat. No. 5,105,377, which is a digital virtual earth algorithm which develops a reference signal by subtracting an equalized anti-noise signal of its own from the residual signal.
Accordingly, an object of this invention is to provide an active noise cancellation headset in which the residual microphone is used to pick-up the user's speech for communication.
A further object of this invention is to use a small electret microphone in an active noise cancellation headset to improve voice intelligibility.
Another object of this invention is to provide a hands-free active noise canceling headset where the outward communication path is handled by microphones in the earpieces.
These and other objects will become apparent when reference is had to the accompanying description and drawings in which:
FIG. 1 is a diagrammatic view of the headset of this invention and the circuitry therefore.
FIG. 2 shows a circuit for using residual microphones for communications
An active noise canceling headset system is shown in FIG. 1 as 10. It consists of two independent noise canceling/systems, such as 11 (only one is shown in the figure), each of which has a residual microphone 12 located at the ear to sense any remaining noise, a system controller 13 to synthesize the anti-noise signal and a headset driver to deliver the anti-noise to the vicinity of the ear. The system components: an LMS (Least Means Square) adapter 14, an adaptive filter 15 and an equalizer 16.
The headset 17 has an open back. This is the most desirable configuration since it is the lightest in weight and, given the selective nature of our noise canceling algorithms, allows the wearer to hear warning signals and external communications thereby increasing user safety.
It has anti-noise speakers 18 to generate sound to cancel unwanted environment noise.
The algorithm used is the digital virtual earth algorithm which develops a reference signal by subtracting an equalized version of its own anti-noise signal from the residual signal, It has been shown to be highly effective in headsets for simple noise environments (a small number of harmonics) even when the noise signal is rapidly varying (as in a siren noise canceling headset). The Least Means Square (LMS) adaption shown is a Filtered-X version which has inherent compensation for the effects of the feedback delays around the loop.
The headset driver (or speaker) is capable of producing the anti-noise at the same level as the noise to be cancelled. It has little or no distortion and has a minimum of input-to-output delay as any delay in the feedback loop slows down the system adaptation rate.
The residual microphone 12 is typically a small electret (capacitive) microphone that is mounted on the driver frame 19 near the ear. It faithfully reproduces the sound that remains at the ear after cancellation so that the controller can make further adjustments to the anti-noise signal.
An example of an application of this headset is in emergency vehicles which use high level sirens to alert
REFERENCES:
patent: 2972018 (1961-02-01), Hawley et al.
patent: 4258235 (1981-03-01), Watson
patent: 4654871 (1987-03-01), Chaplin
patent: 4677677 (1987-06-01), Eriksson
patent: 4736432 (1988-04-01), Cantrell
patent: 4953217 (1990-08-01), Twiney et al.
patent: 4977600 (1990-12-01), Ziegler
patent: 5001763 (1991-03-01), Moseley
patent: 5033082 (1991-07-01), Eriksson et al.
patent: 5046103 (1991-09-01), Warnaka
patent: 5091954 (1992-02-01), Sasaki et al.
patent: 5105377 (1992-04-01), Ziegler
patent: 5182774 (1993-01-01), Bourk
patent: 5402497 (1995-03-01), Nishimoto
patent: 5481615 (1996-01-01), Eatwell
Claybaugh David
Denenberg Jeffrey N.
Harvey Min Oh
Kuntz Curtis
Noise Cancellation Technologies, Inc.
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