An autocorrelation model with place dependence to account for the effect of harmonic number on fundamental frequency discrimination

Fundamental frequency (f₀) difference limens (DLs) were measured as a function of f₀ for sine- and random-phase harmonic complexes, bandpass filtered with 3-dB cutoff frequencies of 2.5 and 3.5 kHz (low region) or 5 and 7 kHz (high region), and presented at an average 15 dB sensation level (approximately 48 dB SPL) per component in a wideband background noise. Fundamental frequencies ranged from 50 to 300 Hz and 100 to 600 Hz in the low and high spectral regions, respectively. In each spectral region, f₀ DLs improved dramatically with increasing f₀ as approximately the tenth harmonic appeared in the passband. Generally, f₀ DLs for complexes with similar harmonic numbers were similar in the two spectral regions. The dependence of f₀ discrimination on harmonic number presents a significant challenge to autocorrelation (AC) models of pitch, in which predictions generally depend more on spectral region than harmonic number. A modification involving a "lag window" is proposed and tested, restricting the AC representation to a limited range of lags relative to each channel's characteristic frequency. This modified unitary pitch model was able to account for the dependence of f₀ DLs on harmonic number, although this correct behavior was not based on peripheral harmonic resolvability.