US 8374358

Here is a concise summary of US Patent 8,374,358.

Title: Method for determining a noise reference signal for noise compensation and/or noise reduction

Assignee: The current assignee of record is Cerence Operating Co. The original assignee was Nuance Communications Inc.

Inventors: Markus Buck, Tobias Wolff, Toby Christian Lawin-Ore, Samuel Ngouoko Mboungueng, Gerhard Schmidt

Filing Date: March 29, 2010

Issue Date: February 12, 2013

Abstract: The invention provides a method for determining a noise reference signal for noise compensation and/or noise reduction. A first audio signal on a first signal path and a second audio signal on a second signal path are received. The first audio signal is filtered using a first adaptive filter to obtain a first filtered audio signal. The second audio signal is filtered using a second adaptive filter to obtain a second filtered audio signal. The first and the second filtered audio signal are combined to obtain the noise reference signal. The first and the second adaptive filter are adapted such as to minimize a wanted signal component in the noise reference signal.

Plain-Language Overview of Independent Claims:

This patent has three independent claims:

Claim 1: A method for determining a noise reference signal.
This claim describes a method to create a clean "noise reference" signal, which is a signal that contains only background noise without a desired sound, like speech. The method involves taking two audio signals from two different paths. Each of these signals is passed through its own adaptive filter (a filter that can adjust its properties). The outputs of these two filters are then combined to produce the final noise reference signal. The key part of this method is that the two adaptive filters are continuously adjusted to remove as much of the desired sound (the "wanted signal") as possible from the final combined signal, leaving primarily the background noise.

Claim 16: A method for processing an audio signal for noise compensation.
This claim describes a full noise-cancellation process that uses the noise reference signal created by the method in Claim 1. It starts by generating the noise reference signal as described above. This noise reference signal is then passed through a third adaptive filter. The output of this third filter, which is an estimate of the noise present in the original audio, is then subtracted from the first original audio signal. The result is a final audio signal with the background noise significantly reduced.

Claim 20: A system for audio signal processing.
This claim describes a physical system designed to perform the method outlined in the previous claims. The system includes a receiver to get the two initial audio signals. It has a first adaptive filter for the first signal and a second adaptive filter for the second signal. A subtractor (or a similar component) is included to combine the outputs of these two filters to create the noise reference signal. The system is designed so that the two adaptive filters can be adjusted to minimize the desired audio signal in their combined output.

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