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The processing and perception of size information in speech sounds
David R R Smith1, Roy D Patterson, Richard Turner
1Centre for Neural Basis of Hearing, Department of Physiology, University of Cambridge, Cambridge CB2 3EG, United Kingdom.
The Journal of the Acoustical Society of America
|February 12, 2005
Summary
The auditory system scales speech sounds to perceive speaker size and recognize vowels, even when sounds are altered beyond the typical human range. This demonstrates an automatic normalization mechanism for vocal tract size information.
Area of Science:
- Auditory perception
- Speech processing
- Psychoacoustics
Background:
- Speech sounds contain vocal tract size information, influencing formant frequencies as children grow.
- A hypothesized auditory scaling transform separates size from shape information to improve perception and recognition.
- Previous research suggests the auditory system may normalize for vocal tract size.
Purpose of the Study:
- To investigate the auditory system's capacity for vocal tract size normalization.
- To gather evidence supporting an auditory scaling mechanism for speech perception.
- To test the limits of size discrimination and vowel recognition under acoustic scaling.
Main Methods:
- Conducted size discrimination experiments using vowels scaled to simulate diverse vocal tract sizes.
- Performed vowel recognition experiments with scaled vowel sounds.
- Manipulated vowel formants and pitch to represent speakers with significantly different vocal tract lengths and sizes.
Main Results:
- Listeners demonstrated accurate discrimination of relative speaker size across a wide range of scaled vowels.
- Vowel recognition performance remained high for both normal and extensively scaled vowel sounds.
- The auditory system effectively processed scaled sounds, indicating robust size normalization.
Conclusions:
- The auditory system automatically normalizes for vocal tract size information present in speech sounds.
- Auditory scaling mechanisms enhance both the perception of speaker size and the recognition of speech.
- These findings support the hypothesis of an adaptive auditory system that processes acoustic variations related to speaker size.