Methods, devices and systems for signal processing an audio signal in a hearing device to determine whether the signal is tonal. The signal is converted at each of a series of successive time windows into samples in the frequency domain across multiple subbands. For at least one of the subbands, a normalized cross-correlation is calculated between two different samples in the same subband. A metric resulting from the calculation is compared to a predetermined threshold to provide a measure of whether the signal is tonal. The signal is considered to be tonal in the frequency of the subband when the metric is greater than or equal to the predetermined threshold, and the signal is considered to be not tonal in the frequency of the subband when the metric is less than the predetermined threshold.