Scientific Article

Sound power of speech between 63 Hz and 20 kHz at a normal vocal effort level

Acoustics Research Unit, School of Architecture, Abercromby Square, University of Liverpool, Liverpool L69 7ZN, United Kingdom

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Received: 6 February 2026
Accepted: 1 June 2026

Abstract

This paper reports anechoic measurements of speech (720 IEEE sentences) produced at a normal vocal effort by 12 native British English speakers (six male, six female) over a hemispherical region (1 m radius) on one side of the talker to allow calculation of the sound power as well as an assessment of the on-axis sound pressure level and directivity. One-third octave bands were measured from 63 Hz to 20 kHz to include the Extended High Frequency (EHF) range above 7 kHz. In the low-frequency range (below 200 Hz), male talkers had higher levels than female talkers in the 100 Hz and 125 Hz one-third octave bands, and only male talkers had measurable levels in the 63 Hz and 80 Hz bands. In the mid-frequency range (200 Hz–4 kHz) there was a difference between male and female talkers in the 800 Hz one-third octave band where females were ≈3 dB higher than males for the on-axis sound pressure level and ≈2 dB higher for the sound power level. In the high-frequency range (5 kHz–20 kHz), no statistically significant differences were found between male and female talkers; although there were large variations between talkers and between sentences that did, and did not contain the fricatives and the unvoiced affricate . The results show that the definition of a unisex talker spectrum (average of male and female talkers) for the on-axis sound pressure level or sound power level is reasonable between the 160 Hz and 20 kHz one-third octave bands, and between the 125 Hz and 16 kHz octave bands.