Detection of random amplitude modulation

摘要

The main objective of this study was to determine the detection thresholds of random amplitude modulation (RAM) as a function of modulation and carrier frequency (f(c)). The RAM was obtained by amplitude modulation (AM) of pure-tone carriers by specially generated sample functions (modulators). The experiment concerned the detection thresholds of AM stimuli for random amplitude changes at constant modulation frequency (f(m)) and simultaneous random changes in amplitude and modulation frequency. The data showed that, the detection thresholds for random amplitude modulation at constant modulation frequency [RAM(f(m) const)] tend to be, in a limited range of f(m), 8-14 dB lower than those for sinusoidal amplitude modulation (SAM). The detection thresholds for random amplitude and modulation frequency [RAM(f(m) random)] were 3-6 dB lower than the RAM(f(m) const) thresholds for high f(c) and f(m). An analysis of the responses of a set of bandpass filters (channels) stimulated by the RAM and SAM signals showed that for the middle and high carrier frequencies, there was a good correspondence between the responses of a set of bandpass filters used and the RAM and SAM detection thresholds. [References: 44]