US 6,480,821 B2 · Methods and apparatus for reducing noise associated with an electrical speech signal

Abstract

A system for enhancing the signal-to-noise ratio of a speech signal is avoided. A plurality of local energy maximums associated with a speech signal are determined. Presumably, each of these local energy maximums defines a speech pitch period. Typically, human pitch periods are approximately 100-400 Hz depending on the sex and age of the speaker. Because human speech typically includes more energy near the beginning of a pitch period than at the end of the pitch period, and background noise tends to remain relatively constant throughout the pitch period, the speech signal may be enhanced by increasing the energy associated with the beginning of the pitch period and/or by decreasing the energy associated with the end of the pitch period. Preferably, the amount of energy increase in the earlier portion of the pitch period is approximately equal to the amount of energy reduction in the later portion of the pitch period. In this manner, the total energy remains the constant.

Claims27

Dependent claims

A method of processing an electrical speech signal to reduce a noise portion of the electrical speech signal, the method comprising the steps of:

determining a plurality of energy levels associated with the electrical speech signal;
selecting a first local maximum energy level and a second local maximum energy level from the plurality of energy levels, the first local maximum energy level and the second local maximum energy level being separated by a time period;
determining a primary time window based on the first local maximum energy level, the primary time window excluding the second local maximum energy level, the primary time window being smaller than the time period;
determining a primary energy level associated with the electrical speech signal by summing a first subset of the plurality of energy levels, the first subset being defined by the primary time window;
determining a secondary time window based on the second local maximum energy level, the secondary time window excluding the first local maximum energy level, the secondary time window being smaller than the time period;
determining a secondary energy level associated with the electrical speech signal by summing a second subset of the plurality of energy levels, the second subset being defined by the secondary time window;
modifying the electrical speech signal such that the primary energy level is increased by a predefined amount;
and
modifying the electrical speech signal such that the secondary energy level is decreased by the predefined amount.

6 more elements

Dependencies are inferred from the claim text.

Methods and apparatus for reducing noise associated with an electrical speech signal

Life of this patent

Methods and apparatus for reducing noise associated with an electrical speech signal

Life of this patent

Abstract

Claims27