8. A method of enhancing speech in a hearing aid, involving the steps of providing an input signal, splitting the input signal into a plurality of frequency bands, deriving an envelope signal from the input signal, determining at least one detected, voiced speech frequency from the envelope signal, determining a voiced speech probability from the number of detected, voiced speech frequencies, determining an unvoiced speech level from the input signal, identifying the frequency bands of the plurality of frequency bands where the speech level is higher than the noise level by a first, predetermined amount, and increasing the level of those frequency bands in the output signal of the hearing aid by a second, predetermined amount.
8. A method of enhancing speech in a hearing aid, involving the steps of providing an input signal, splitting the input signal into a plurality of frequency bands, deriving an envelope signal from the input signal, determining at least one detected, voiced speech frequency from the envelope signal, determining a voiced speech probability from the number of detected, voiced speech frequencies, determining an unvoiced speech level from the input signal, identifying the frequency bands of the plurality of frequency bands where the speech level is higher than the noise level by a first, predetermined amount, and increasing the level of those frequency bands in the output signal of the hearing aid by a second, predetermined amount. 10. The method according to claim 8 , wherein the step of determining an unvoiced speech level involves the steps of deriving a zero-crossing rate count of the input signal, deriving an averaged zero-crossing rate count from the input signal and the zero-crossing rate count, comparing the zero-crossing rate count with the averaged zero-crossing rate count, and calculating an unvoiced speech level by determining if the zero-crossing rate is higher than the averaged zero-crossing rate by a predetermined amount.