Evolution of time‐varying loudness during nonlinear propagation of broadband noise

Abstract

Previous work has shown that loudness and sound quality metrics that rely exclusively on the power spectrum do not adequately represent the perceptual impact of nonlinearly propagated noise. [K.L. Gee et al., J. Acoust. Soc. Am. 121, EL1–EL7 (2007)]. This discrepancy between spectral content and perceptual quality appears to be related to the formation of acoustic shocks in the pressure waveform. Because time‐varying loudness (TVL) more accurately represents temporal effects in the ear, a preliminary investigation of the response of TVL to nonlinearly propagated noise has been carried out. TVL has been calculated for a shaped broadband noise waveform as it is nonlinearly propagated using a generalized Burgers equation‐based model. The same waveform is also propagated using a linear model and the TVL for the nonlinear and linear waveforms are compared and discussed. An additional comparison carried out is that of the nonlinear waveform’s TVL and the TVL for the nonlinear waveform with its Fourier phase randomized. This phase randomization preserves the nonlinear waveform’s power spectrum but eliminates the acoustic shocks in the time domain. The nonlinear waveform shows more variation in both short and long term loudness than either the linear or the phase‐randomized waveform.