Reorganization of the auditory-perceptual space across the human vocal range

TL;DR

This study investigates how human vowel perception changes across a broad vocal frequency range, revealing spectral shifts and clustering at higher pitches, emphasizing spectral shape's role in vowel recognition and language evolution.

Contribution

It provides new insights into spectral shifts in vowel perception across frequencies and highlights the importance of spectral shape in understanding language and phonetic processing.

Findings

Vowel recognition declines at higher pitches for non-/i a u/ vowels.

Spectral shifts correlate with vowel height and frontness as fundamental frequency increases.

Clustering of vowels around /i a u/ occurs above 523 Hz.

Abstract

We analyzed the auditory-perceptual space across a substantial portion of the human vocal range (220-1046 Hz) using multidimensional scaling analysis of cochlea-scaled spectra from 250-ms vowel segments, initially studied in Friedrichs et al. (2017) J. Acoust. Soc. Am. 142 1025-1033. The dataset comprised the vowels /i y e {\o} {\epsilon} a o u/ (N=240) produced by three native German female speakers, encompassing a broad range of their respective voice frequency ranges. The initial study demonstrated that, during a closed-set identification task involving 21 listeners, the point vowels /i a u/ were significantly recognized at fundamental frequencies (fo) nearing 1 kHz, whereas the recognition of other vowels decreased at higher pitches. Building on these findings, our study revealed systematic spectral shifts associated with vowel height and frontness as fo increased, with a notable clustering around /i a u/ above 523 Hz. These observations underscore the pivotal role of spectral shape in vowel perception, illustrating the reliance on acoustic anchors at higher pitches. Furthermore, this study sheds light on the quantal nature of these vowels and their potential impact on language evolution, offering a plausible explanation for their widespread presence in the world's languages.