Noise Reduction
First Claim
1. A signal processor for estimating noise power in an audio signal, the signal processor comprising:
- a filter function for generating a series of power values, each power value representing the power in the audio signal at a respective one of a plurality of frequency bands;
a signal classification function for analysing successive portions of the audio signal to assess whether each portion contains features characteristic of speech, and for classifying each portion in dependence on that analysis;
a correction function for estimating a minimum power value in a time-limited part of the audio signal, estimating the total noise power in that part of the audio signal and forming a correction factor dependent on the ratio of the minimum power value to the estimated total noise power, the correction function being configured to estimate the minimum power value and the total noise power over only those portions of the time-limited part of the signal that are classified by the signal classification function as being less characteristic of speech; and
a noise estimation function for estimating noise in the audio signal in dependence on the power values output by the filter function and the correction factor formed by the correction function.
3 Assignments
0 Petitions
Accused Products
Abstract
A signal processor for estimating noise power in an audio signal includes a filter unit for generating a series of power values, each power value representing the power in the audio signal at a respective one of a plurality of frequency bands; a signal classification unit for analysing successive portions of the audio signal to assess whether each portion contains features characteristic of speech, and for classifying each portion in dependence on that analysis; a correction unit for estimating a minimum power value in a time-limited part of the audio signal, estimating the total noise power in that part of the audio signal and forming a correction factor dependent on the ratio of the minimum power value to the estimated total noise power, the correction unit being configured to estimate the minimum power value and the total noise power over only those portions of the time-limited part of the signal that are classified by the signal classification unit as being less characteristic of speech; and a noise estimation unit for estimating noise in the audio signal in dependence on the power values output by the filter unit and the correction factor formed by the correction unit.
-
Citations
72 Claims
-
1. A signal processor for estimating noise power in an audio signal, the signal processor comprising:
-
a filter function for generating a series of power values, each power value representing the power in the audio signal at a respective one of a plurality of frequency bands; a signal classification function for analysing successive portions of the audio signal to assess whether each portion contains features characteristic of speech, and for classifying each portion in dependence on that analysis; a correction function for estimating a minimum power value in a time-limited part of the audio signal, estimating the total noise power in that part of the audio signal and forming a correction factor dependent on the ratio of the minimum power value to the estimated total noise power, the correction function being configured to estimate the minimum power value and the total noise power over only those portions of the time-limited part of the signal that are classified by the signal classification function as being less characteristic of speech; and a noise estimation function for estimating noise in the audio signal in dependence on the power values output by the filter function and the correction factor formed by the correction function. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
-
-
16. A method for estimating noise power in an audio signal, the method comprising:
-
generating a series of power values, each power value representing the power in the audio signal at a respective one of a plurality of frequency bands; analysing successive portions of the audio signal to assess whether each portion contains features characteristic of speech, and classifying each portion in dependence on that analysis; estimating a minimum power value in a time-limited part of the audio signal, estimating the total noise power in that part of the audio signal and forming a correction factor dependent on the ratio of the minimum power value to the estimated total noise power, the method comprising estimating the minimum power value and the total noise power over only those portions of the time-limited part of the signal that have been classified in the analysing step as being less characteristic of speech; and estimating noise in the audio signal in dependence on the estimated power values and the formed correction factor. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
-
-
17. A method as claimed in claim 17, wherein the step of generating a series of power values comprises implementing a Fourier transform.
-
31. A signal processor for estimating noise in an audio signal, the signal processor comprising:
-
a frequency analysis function for performing frequency analysis on the audio signal to periodically determine the power of the signal in each of a plurality of frequency ranges; an aggregation function for forming a plurality of power data sets, each of the power data sets representing the powers determined by the frequency analysis function over a respective frequency range and over a time period, and each of the components of at least one of the power data sets being formed by combining the powers determined by the frequency analysis function for two or more frequency ranges; and a minimisation function for determining the minima of each of the power data sets; and a noise estimation function for estimating noise in the audio signal in dependence on the minima determined by the minimisation function. - View Dependent Claims (32, 33, 34, 35, 36, 37, 38)
-
-
39. A method for estimating noise in an audio signal, the method comprising:
-
performing frequency analysis on the audio signal to periodically determine the power of the signal in each of a plurality of frequency ranges; forming a plurality of power data sets, each of the power data sets representing the powers determined over a respective frequency range and over a time period, and each of the components of at least one of the power data sets being formed by combining the powers determined by the frequency analysis function for two or more frequency ranges; and determining the minima of each of the power data sets; and estimating noise in the audio signal in dependence on the determined minima. - View Dependent Claims (40, 41, 42, 43, 44, 45, 46)
-
-
47. A signal processor for reducing noise in an audio signal, the signal processor comprising:
-
an analysis function for analysing the audio signal to form one or more first intermediate signals; a gain function for applying a determined gain to the or each first intermediate signal to form one or more second intermediate signals; and a synthesis function for synthesising a reduced noise audio signal from the second intermediate signal(s); and a gain determination function configured to determine the gain to be applied to the or each first intermediate signal as the Weiner gain of the respective intermediate signal smoothed by the instantaneous variance of the Weiner gain. - View Dependent Claims (48, 49, 50, 51, 52, 53, 54)
-
-
55. A method for reducing noise in an audio signal, the method comprising:
-
analysing the audio signal to form one or more first intermediate signals; applying a determined gain to the or each first intermediate signal to form one or more second intermediate signals; and synthesising a reduced noise audio signal from the second intermediate signal(s); and determining the gain to be applied to the or each first intermediate signal as the Weiner gain of the respective intermediate signal smoothed by the instantaneous variance of the Weiner gain. - View Dependent Claims (56, 57, 58, 59, 60, 61, 62)
-
-
63. A signal processor for reducing noise in an audio signal, the signal processor comprising:
-
an analysis function for analysing the audio signal to form one or more first intermediate signals; a gain function for applying a determined gain to the or each first intermediate signal to form one or more second intermediate signals; and a synthesis function for synthesising a reduced noise audio signal from the second intermediate signal(s); a signal classification function for analysing successive portions of the audio signal to assess whether each portion contains features characteristic of speech, and for classifying each portion in dependence on that analysis; a gain determination function configured to determine the gain to be applied to each portion of the or each first intermediate signal according to a first algorithm if the portion of the audio signal corresponding to that portion of the first intermediate signal has been classified by the signal classification function as containing features characteristic of speech, and according to a second algorithm otherwise. - View Dependent Claims (64, 65, 66, 67)
-
-
68. A method for reducing noise in an audio signal, the method comprising:
- an analysis function for analysing the audio signal to form one or more first intermediate signals;
a gain function for applying a determined gain to the or each first intermediate signal to form one or more second intermediate signals; and
a synthesis function for synthesising a reduced noise audio signal from the second intermediate signal(s);
a signal classification function for analysing successive portions of the audio signal to assess whether each portion contains features characteristic of speech, and for classifying each portion in dependence on that analysis;
a gain determination function configured to determine the gain to be applied to each portion of the or each first intermediate signal according to a first algorithm if the portion of the audio signal corresponding to that portion of the first intermediate signal has been classified by the signal classification function as containing features characteristic of speech, and according to a second algorithm otherwise. - View Dependent Claims (69, 70, 71, 72)
- an analysis function for analysing the audio signal to form one or more first intermediate signals;
Specification