The processing and perception of size information in speech sounds

Abstract

There is information in speech sounds about the length of the vocal tract; specifically, as a child grows, the resonators in the vocal tract grow and the formant frequencies of the vowels decrease. It has been hypothesized that the auditory system applies a scale transform to all sounds to segregate size information from resonator shape information, and thereby enhance both size perception and speech recognition [Irino and Patterson, Speech Commun. 36, 181-203 (2002)]. This paper describes size discrimination experiments and vowel recognition experiments designed to provide evidence for an auditory scaling mechanism. Vowels were scaled to represent people with vocal tracts much longer and shorter than normal, and with pitches much higher and lower than normal. The results of the discrimination experiments show that listeners can make fine judgments about the relative size of speakers, and they can do so for vowels scaled well beyond the normal range. Similarly, the recognition experiments show good performance for vowels in the normal range, and for vowels scaled well beyond the normal range of experience. Together, the experiments support the hypothesis that the auditory system automatically normalizes for the size information in communication sounds.

Morphing rhesus monkey vocalizations

“…The procedure can now be used to morph between many different types of vocalizations, such as those from different individuals, different genders and across species or call types. This broadens the scope of the questions that can be asked in behavioral and neurophysiological studies of vocal recognition, and has the potential to bridge approaches that manipulate the features of natural and ethologically relevant vocalizations (e.g., Fitch and Fritz, 2006;Ghazanfar et al, 2007;Gifford et al, 2005;Smith et al, 2005) with the more common approach of using controlled acoustical stimuli to probe the function of the auditory system.…”

“…Scientists have been using various algorithms and software packages to automate the analysis, extraction and independent manipulation of the different frequency components of 'voiced' sounds (Fitch and Fritz, 2006;Ghazanfar et al, 2007;Smith et al, 2005;von Kriegstein et al, 2007), also see the Praat software at http://www.fon.hum.uva.nl/praat/. This work suggests that the gradual morphing of vocalizations is possible if 'voiced' sounds are used which have prominent frequency and harmonic structure.…”

Are men better than women at acoustic size judgements?

“…This 'size normalization' appears to be applied to all sounds at a relatively early stage in auditory processing [16], suggesting that humans have dedicated perceptual mechanisms for automatically processing size-related formant information. Our results show that this ability is more developed in men, and support the idea that sexual selection might have played a role in the evolution of this key prerequisite of speech perception [1].…”

Illusory Vowels Resulting from Perceptual Continuity: A Functional Magnetic Resonance Imaging Study

“…Because only four different vowels were used, we roved the f0 of each vowel to create five different exemplars of a particular vowel (see Table 1). Following Smith, Patterson, Turner, Kawahara, and Irino's (2005) observation that a proportionate increase of the formant and fundamental frequencies of a vowel can keep its identity stable but changes speaker identity, we increased f1 and f2 in proportion to the increase in f0, and fine-adjusted formant frequencies such that the ''color'' of the vowel was as similar as possible across all five tokens (Table 1).…”