Design of linear time-domain filters for hearing protector modeling.
J Acoust Soc Am 2006 Nov; 120(5):3162
Accurately modelinghearing protectors for predicting the hazard underneath them is of interest to many. This project modeled the single transfer path through the hearing protector from the free field to the ear drum, as an extension to the frequency-domain modeling method presented by Price and Kalb [J. Acoust. Soc. Am. 103, 2878 (1998)]. First, the real ear attenuation at threshold (REAT) data from the hearing protectors (muff and plugs) were converted to linear quantities and curve fit to form a continuous function of frequency, while preserving the low-pass characteristic. The resulting magnitude was combined with the head-related transfer function (HRTF) to form the magnitude of the total transfer function. Using complex cepstrum, a stable, complex frequency response function (FRF) was created by assuming a minimum phase transfer path. System identification methods were used to fit the FRF data to a parametric model that was converted to an infinite impulse response (IIR) digital filter. Subject-fit REAT data were used in order to represent real-world usage. Imperfect usage was modeled by derating the subject fit data by 1 standard deviation (SD). Tests on an artificial head are conducted to evaluate the filters in the time and frequency domains.
Laboratory-testing; Impulse-noise; Acoustical-materials; Acoustical-measurements; Acoustics; Shock-waves; Sound; Sound-analyzers; Sound-propagation; Ear-protection; Ear-protectors; Hearing-protection; Noise-analysis; Noise-levels; Noise-sources
Jeffrey S. Vipperman, Dept. of Mech. Eng., Univ. of Pittsburgh, 648 Benedum Hall, Pittsburgh, PA 15261
Journal of the Acoustical Society of America