Noise suppressing method and a noise suppressor for applying the noise suppressing method
First Claim
1. A method in a communication device for suppressing noise of a first signal, captured via a primary microphone, arranged on the communication device such that it is capable of capturing noise and intermittent speech, the noise suppression being executed by processing signal power spectrum estimates of the first signal and a second signal, captured via a reference microphone arranged on the communication device, such that it is capable of capturing noise at substantially the same signal level as the primary microphone and speech at a lower signal level than the primary microphone, the method comprising:
- determining, on the basis of characteristics of the signal power spectrum estimate of the first signal, whether the first signal comprises non-stationary signal components or substantially stationary noise;
responsive to determining that the first signal comprises substantially non-stationary signal components, determining, on the basis of an inter-microphone gain offset and a ratio of the first signal and the second signal, whether the first signal comprises near-field signal components or substantially far-field noise;
responsive to determining that the first signal comprises substantially stationary noise, updating a noise power spectrum estimate of the first signal with a stationary noise power spectrum estimate;
responsive to determining that the first signal comprises substantially far-field noise, updating the noise power spectrum estimate of the first signal with a far-field noise power spectrum estimate;
computing a frequency response of a noise suppressing filter on the basis of the noise power spectrum estimate,suppressing noise from the first signal by applying the noise suppressing filter with said frequency response on said first signal; and
calculating a signal power spectrum ratio as a ratio of a first power spectrum estimated for the first signal and a second power spectrum estimated for the second signal, and eitherresponsive to the power spectrum ratio being calculated when the first signal was determined to comprise substantially stationary noise, updating the inter-microphone gain offset on the basis of the signal power spectrum ratio, orresponsive to the power spectrum ratio being calculated when the first signal was determined to comprise non-stationary signal components, determining whether the first signal comprises substantially far-field noise by comparing the signal power spectrum ratio to the most recently updated inter-microphone gain offset.
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Accused Products
Abstract
A method for suppressing noise of a first signal captured via a primary microphone is provided. A primary and a reference microphone are arranged on a communication device to capture noise and intermittent speech. A determination is made whether the first signal comprises non-stationary signal components or substantially stationary noise, and whether the first signal comprises substantially far-field noise in case it was determined that it comprises non-stationary signal components. A noise power spectrum estimate of the first signal is updated with a stationary noise power spectrum estimate if the first signal is considered to comprise substantially stationary noise or a far-field noise power spectrum estimate if the first signal is considered to comprise substantially far-field noise. A frequency response is computed on the basis of the estimated noise power spectrum. Noise from the first signal is suppressed by applying the frequency response on the first signal.
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Citations
22 Claims
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1. A method in a communication device for suppressing noise of a first signal, captured via a primary microphone, arranged on the communication device such that it is capable of capturing noise and intermittent speech, the noise suppression being executed by processing signal power spectrum estimates of the first signal and a second signal, captured via a reference microphone arranged on the communication device, such that it is capable of capturing noise at substantially the same signal level as the primary microphone and speech at a lower signal level than the primary microphone, the method comprising:
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determining, on the basis of characteristics of the signal power spectrum estimate of the first signal, whether the first signal comprises non-stationary signal components or substantially stationary noise; responsive to determining that the first signal comprises substantially non-stationary signal components, determining, on the basis of an inter-microphone gain offset and a ratio of the first signal and the second signal, whether the first signal comprises near-field signal components or substantially far-field noise; responsive to determining that the first signal comprises substantially stationary noise, updating a noise power spectrum estimate of the first signal with a stationary noise power spectrum estimate; responsive to determining that the first signal comprises substantially far-field noise, updating the noise power spectrum estimate of the first signal with a far-field noise power spectrum estimate; computing a frequency response of a noise suppressing filter on the basis of the noise power spectrum estimate, suppressing noise from the first signal by applying the noise suppressing filter with said frequency response on said first signal; and calculating a signal power spectrum ratio as a ratio of a first power spectrum estimated for the first signal and a second power spectrum estimated for the second signal, and either responsive to the power spectrum ratio being calculated when the first signal was determined to comprise substantially stationary noise, updating the inter-microphone gain offset on the basis of the signal power spectrum ratio, or responsive to the power spectrum ratio being calculated when the first signal was determined to comprise non-stationary signal components, determining whether the first signal comprises substantially far-field noise by comparing the signal power spectrum ratio to the most recently updated inter-microphone gain offset. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A noise suppressor for suppressing noise of a first signal, captured via a primary microphone, arranged on a communication device such that it is capable of capturing noise and intermittent speech, the noise suppressor being configured to suppress noise by processing signal power spectrum estimates of the first signal and a second signal, captured via a reference microphone arranged on the communication device such that it is capable of capturing noise at substantially the same signal level as the primary microphone and speech at a lower signal level than the primary microphone, the noise suppressor comprising:
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a stationarity evaluating unit configured to determine, on the basis of characteristics of the signal power spectrum estimate of the first signal, whether the first signal comprises non-stationary signal components or substantially stationary noise; a far-field evaluating unit configured to respond to determining that the first signal comprises substantially non-stationary signal components by determining, on the basis of an inter-microphone gain offset and a ratio of the first signal and the second signal, whether the first signal comprises near-field signal components or substantially far-field noise; a noise power spectrum updating unit configured to respond to determining that the first signal comprises substantially stationary noise by updating a noise power spectrum estimate of the first signal with a stationary noise power spectrum estimate, the noise power spectrum updating unit is further configured to respond to determining that the first signal comprises substantially far-field noise by updating the noise power spectrum estimate of the first signal with a far-field noise power spectrum estimate; a filtering unit configured to compute a frequency response of a noise suppressing filter on the basis of the noise power spectrum estimate, and to suppress noise from the first signal by applying the noise suppressing filter with said frequency response on said first signal; a power ratio calculating unit configured to calculate a signal power spectrum ratio as a ratio of a first power spectrum estimated for the first signal and a second power spectrum estimated for the second signal; an inter-microphone gain offset calculating unit configured to respond to the power spectrum ratio being calculated when the first signal was determined to comprise substantially stationary noise, by updating the inter-microphone gain offset on the basis of the signal power spectrum ratio, and a far-field noise power spectrum estimating unit configured to respond to the power spectrum ratio being calculated when the first signal was determined to comprise non-stationary signal components by determining whether the first signal comprises substantially far-field noise by comparing the signal power spectrum to the previously updated inter-microphone gain offset. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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Specification