Method and apparatus for audio signal processing

• US 20050123150A1
• Filed: 02/03/2003
• Published: 06/09/2005
• Est. Priority Date: 02/01/2002
• Status: Active Grant

• Current Assignee: Cedar Audio Limited
• Original Assignee: Cedar Audio Limited
• Inventors: Betts, David Anthony
• Granted Patent: US 7,978,862 B2
• Time in Patent Office: Days
• US Class Current: 381/94.300
• CPC Class Codes: G10L 21/0208 Noise filtering

Abstract

A sampled digital audio signal is displayed on a spectrogram, in terms of frequency vs. time. An unwanted noise in the signal is visible in the spectrogram and the portion of the signal containing the unwanted noise can be selected using time and frequency constraints. An estimate for the signal within the selected portion is then interpolated on the basis of desired portions of the signal outside the time constraints defining the selected portion. The interpolated estimate can then be used to attenuate or remove the unwanted sound

Claims

1-28. -28. (canceled)

44. A method for the attention or removal of an unwanted sound from an audio signal in which an AR model is used to interpolate an estimate for a set of samples in the signal from the surrounding samples, in which a modification is applied to the excitation signal equations that makes the interpolated signal converge to a chosen template signal.

45. The method according to claim 44, in which the template signal has the same power spectrum as the surrounding signal.

46. The method according to claim 44, in which the interpolated signal is constrained to converge to the chosen template signal within the selected constraints or band(s).

47. The method according to claim 46, in which the template signal has the same power spectrum as the surrounding signal, thereby preventing inappropriate power loss in the interpolated data.

48. The method according to claim 44, comprising the step of simultaneously interpolating two or more discrete frequency bands.

49. The method according to claim 44, in which a spectrogram is used to define the discrete frequency constraint or constraints and to define the set of samples to be interpolated and to define the set of samples that are used to derive the signal model.

50. The method according to claim 44, characterized by the interpolated signal being constrained to converge to the chosen template signal within the selected constraint(s).

51. The method according to claim 50, characterized by the template signal having the same power spectrum as the surrounding signal, thereby preventing inappropriate power loss in the interpolated data.

52. The method according to claim 44, characterized by the simultaneous interpolation of two or more discrete frequency constraints or bands, and/or two or more discrete regions bounded by time constraints.

53. The method according to claim 50, characterized by the use of a spectrogram to define the discrete frequency constraints and to define the set of samples to be interpolated and to define the set of samples that are used to derive the signal model.

54. The method according to claim 44, in which the interpolated signal affects the signal spectrum inside the selected constraint(s) without adversely affecting the signal spectrum that lies outside the selected constraints(s).

55. The method according to claim 44, in which the interpolated signal affects the signal spectrum that lies outside the selected constraint(s) without adversely affecting the signal spectrum inside the selected constraint(s).

56. A method in which mathematical techniques are used to interpolate an estimate for a set of samples in a digital audio signal from surrounding samples, characterised by the selection of one or more frequency constraints or bands, these being used to constrain the interpolation of the set of samples such that the interpolated signal affects the signal spectrum inside selected constraint(s) or band(s) without adversely affecting the signal spectrum that lies outside the selected constraint(s) or band(s).

57. A method in which mathematical techniques are used to interpolate an estimate for a set of samples in a digital audio signal from surrounding samples, characterised by the selection of one or more frequency constraints or bands, these being used to constrain the interpolation of the set of samples such that the interpolated signal affects the signal spectrum that lies outside the selected constraint(s) or band(s) without adversely affecting the signal spectrum inside selected constraint(s) or band(s).

58. A method in which an AR model is used to interpolate an estimate for a set of samples in a digital audio signal from surrounding samples, characterised by applying a modification to the excitation signal equations that makes the interpolated signal converge to a chosen template signal.