To obtain a device which actualizes spectrum analytic display by displaying frequency components of an input digital signal, which is decomposed into frequency band components, by utilizing normalized information associated with time and frequency, which is calculated by two-dimensional blocks.

An audio PCM signal is supplied to an input terminal 100 and divided by band dividing filters(QMF):101 and 102. The signal from the QMF:101 is sent to an orthogonal converting circuit (MDCT):103 the signal from the QMF:102 is sent to MDCTs 104 and 105; and spectrum data on the frequency axis or MDCT coefficient data obtained by performing MDCT processes respectively are sent to adaptive bit allocation encoding circuits 106 to 108 and a bit allocation calculating circuits 118 while their critical bandwidth is fractionated. The bit allocation calculating circuit 118 obtains normalized information for a certain time and outputs it to a display value calculating circuit 123 to enable dynamic spectrum analytic display.