Noise attenuation system

A noise attenuation system for attenuating noise in a signal, comprising a filter for dividing the signal into a plurality of channels of a predetermined bandwidth, means for calculating the signal strength in each channel and estimating the noise strength in each channel, said system further comprising;

• a buffer for processing of the signal sequentially in distinct time periods of a predetermined length, and having an output coupled to a tonality decision block and said filter, said tonality decision block classifying each period as tonal or toneless,
• a background noise measurement system coupled to said filter and responsive to signals in said plurality of channels, for determining an estimate of background noise strength, said background noise measurement system splitting frequency components of signals from at least one channel into plural frequency ranges during each time period in which a tonal signal is indicated for said channel, and determining from one split frequency range, said background noise strength and a signal to noise ratio for each channel in each time period, a gain calculation block for determining a gain coefficient for each channel in each time period, such that the channel attenuation is increased for a decreasing signal to noise ratio, the gain calculation block coupled to a multiplication block for amplifying the signals in the plurality of channels dependent on the determined gain coefficient, and an assembly filter which reassembles noise attenuated channels to produce a noise attenuated signal.