Patent ID: 7146003

Claim:
A method of calculating noise level in a signal, comprising the steps of: accumulating two sample windows of said signal; calculating energy of said signal between each of said sample windows; calculating the difference in said energy of said signal within each of said sample windows; updating a variance parameter based on said difference; in the event that said variance parameter is less than a predetermined multiple of the energy of said signal within a most recent one of said sample windows then indicating the presence of noise and setting a noise level parameter as a function of the energy of said signal within said most recent one of said sample windows, and in the event that said variance parameter is greater than or equal to said predetermined multiple of the energy of said signal within said most recent one of said sample windows then indicating the absence of noise in said most recent sample window; and in the event that said noise level parameter exceeds the energy of said signal within said most recent one of said sample widows then setting said noise level parameter to equal the energy of said signal within said most recent one of said sample windows, wherein said step of updating said variance parameter further comprises the steps of: comparing said variance parameter to said difference in said energy of said signal within each of said sample windows and setting said variance parameter to the weighted average of the difference and a previous value of the variance parameter; and in the event that said variance parameter is greater than said difference then adjusting said variance parameter with a predetermined decay ratio, and in the event that said variance parameter is less than or equal to said difference then adjusting said variance parameter with a predetermined attack ratio.