Critical modulation frequency and critical band based on random amplitude and frequency changes

The presented paper deals with determination of the critical modulation frequency (CMF) and critical bandwidth in the case of random amplitude and frequency changes in a sinusoidal signal. The critical modulation frequency is the smallest value of modulation frequency for which thresholds for detecting amplitude and frequency modulation, expressed in appropriate modulation indexes (i.e. m and β), reach the same values. Random amplitude and frequency changes of the simple tone were produced in the amplitude and frequency modulation process by random modulating signals. The results of the investigations enable to state that the critical modulation frequency is an increasing function of the carrier frequency. It was also shown that psychoacoustically measurable quantities such as detection thresholds, the critical modulation frequency and quantities connected with it (i.e. critical bandwidth, a range of occurrence of a monaural phase effect), do not depend on a modulating signal character (i.e. whether this signal is periodic or random).