Measuring the critical band for speech.

Area of Science:

• Auditory perception
• Psychoacoustics
• Speech processing

Background:

• Understanding speech perception requires knowledge of auditory frequency resolution.
• Traditional psychoacoustic methods assess frequency resolution using non-speech stimuli.
• The critical band is a key concept in auditory processing.

Purpose of the Study:

• To measure the frequency resolution used by listeners in everyday sentence perception.
• To compare speech-based frequency resolution with traditional psychoacoustic measures.
• To investigate the critical band for speech in different frequency regions.

Main Methods:

• Speech was partitioned into narrow frequency subbands.
• Temporal envelopes of subbands modulated low-noise noise carriers.
• Normal-hearing listeners' speech intelligibility was measured with varying numbers of subbands.

Main Results:

• Speech intelligibility improved with increased frequency partitioning, reaching an asymptote.
• In mid- and high frequencies, the bandwidth for optimal performance matched psychoacoustic critical bands.
• In low frequencies, optimal bandwidths were narrower than predicted by psychoacoustic tuning.

Conclusions:

• Psychoacoustic tuning estimates generally align with listeners' ability to extract spectral detail from speech.
• The critical band for speech aligns with psychoacoustic measures in mid- and high frequencies.
• Low-frequency speech processing may involve finer spectral resolution than predicted by traditional psychoacoustics.