Quantifying slow amplitude and frequency modulations with psychoacoustic models - problems and preliminary solutions

Technical and natural sound are nowadays analyzed not only by means of total sound pressure level over time or FFT analysis but also regarding their temporal changes. Many technical sounds, for instance car and aircraft interior noises, are not constant with time and are perceived as fluctuating or rough. Psychoacoustic models have been developed to quantify the sensations of fluctuation and roughness. Nevertheless models lack of standardization giving rise to different and erroneous results when applied to the same sound within different software packages. Also the models are limited to certain frequencies of modulation and other restrictions such as signal length apply. Physical modulation analysis is less restrictive and can be used to help with identification and quantification of fluctuation and roughness. The present paper will analyze some aspects of analysis of perceivable fluctuations and show how currently available tools for signal analysis can be used to identify and quantify perceived modulations properly.