Patent ID: 8422697

Claim:
A system for estimating the power spectral density of acoustical background noise, the system comprising: a sensor unit for generating a noise signal representative of the background noise; a power spectral density calculation unit that is determines the current power spectral density of the noise signal provides a power spectral density output signal indicative thereof; a time domain signal smoothing unit that smoothes the power spectral density output signal in the time domain and provides a resulting timely smoothed signal indicative thereof; a frequency domain signal smoothing unit that smoothes the timely smoothed signal in the frequency domain and provides a resulting smoothed power spectral density signal indicative thereof; an increment calculation unit that calculates an increment value depending the power spectral density output signal; a decrement calculation unit that calculates of a decrement value depending on the power spectral density output signal; an estimate signal smoothing unit that receives the smoothed power spectral density signal, the increment value and the decrement value and provides an estimated calculation power spectral density of the background noise; where for cases in which the level of the smoothed power spectral density signal increases, the increment value is increased, starting from a minimum increment value, by a predetermined amount until a maximum increment value is reached if at the same time the value of the power spectral density currently determined in a new calculation cycle is larger than the estimate value of the power spectral density of the background noise determined in the previous calculation cycle; and for cases in which the level of the smoothed power spectral density decreases, the decrement value is increased, starting from a minimum decrement value, by a predetermined amount until a maximum decrement value is reached if at the same time the value of the power spectral density currently determined in a new calculation cycle is smaller than the estimate value of the power spectral density of the background noise determined in the previous calculation cycle.