Fluctuation strength and temporal masking patterns of amplitude-modulated broadband noise.

Fluctuation strength of sinusoidally amplitude modulated broadband noise was measured by a magnitude-estimation procedure. Fluctuation strength shows, as a function of modulation frequency, a bandpass characteristic with a maximum around 4 Hz. With increasing modulation depth and sound pressure level, fluctuation strength increases. For the same stimulus parameters as used in the experiments on fluctuation strength, temporal masking of amplitude modulated broadband noise was determined. The level difference delta L between the maximum and the minimum of the resulting temporal masking patterns shows a low-pass characteristic as a function of modulation frequency and increases with increasing modulation depth and sound pressure level. A model of fluctuation strength F based on the depth delta L of the temporal masking pattern and the modulation frequency fmod in relation to 4 Hz is proposed as follows: F approximately delta L/((fmod/4 Hz)+(4 Hz/fmod)). The model accounts for the dependence of fluctuation strength on some essential stimulus parameters. The usefulness of temporal masking patterns as an intermediate value for the description of hearing sensations is confirmed.