Apparatus for encoding digital signals

Apparatus for efficiently encoding a digital signal includes an arrangement (41, 42) for dividing the signal into a number of frequency band signals. The frequency band signals are segmented into blocks and the blocks are orthogonally transformed (43, 44, 45) to form coefficient data. The coefficient data is then quantized (58). A circuit (50) detects whether at least the lowest frequency one of the frequency band signals contains a transient. If so, a control circuit (57; 102; 100) controls processing of at least the lowest frequency band signal so as to reduce the perceptibility of noise in the processed signal. The control circuit may be operative, in the event of detection of a transient, to increase the number of bits used for quantizing at least the lowest frequency band signal, to reduce the block size of at least the lowest frequency band signal, and/or to reduce the level of at least the lowest frequency band signal.