Effect of fundamental frequency removal on mistuned harmonic separation thresholds

Investigating how the auditory system processes harmonics is essential for advancing our understanding of sound segregation mechanisms and for guiding the development of technologies that support speech and music perception in complex listening environments, particularly for aging populations and individuals with hearing loss. Previous studies have investigated the extent of mistuning required for a harmonic to be perceived as distinct from a complex tone and how factors like modulation patterns, onset timing and ear of presentation can influence this threshold. However, the effect of a missing fundamental frequency on mistuned harmonic separation thresholds remains unexplored.

This pilot study, conducted using an adjustment method developed in our lab for this specific application, investigated mistuning thresholds for the first harmonic in complex tones with and without F₀ at 125, 200 and 440 Hz.

Because the F₀ helps define the harmonic structure of a sound, its removal was expected to impair the perceptual framework used to detect pitch deviations, thereby increasing mistuning thresholds, as predicted by current models of pitch perception. Contrary to expectations, the results revealed a significant overall improvement in performance when the F₀ was missing.

These results have important implications for understanding pitch processing as it suggests that the auditory system may more effectively detect pitch irregularities by relying on the harmonic structure of a sound rather than on the presence, or relationship with, its fundamental frequency.