Loudness, Sound Pressure, and Subglottal Pressure in Speech

Three experiments using one speaker and 30 listeners provided correlated data on subglottal pressure, average volume velocity through the glottis, fundamental frequency, effective sound pressure in front of the speaker, and judgments of loudness. Experiment 1: In 12 repetitions each of bee, bay, bar, bore, and boo spoken at various loudnesses, it was found that in the middle range (subglottal pressure) ∝ (effective sound pressure)0.6; and the level of the vowel in bar was about 5 dB greater than in bee or boo produced with the same subglottal pressure. Experiment 2: In 32 repetitions of the vowel /ɑ/ uttered at various loudnesses with the pitch uncontrolled, it was found that an increase of subglottal pressure of about 6.5 cm aq accompanied an increase in frequency of half an octave; and to a first approximation (rate of flow) ∝ (subglottal pressure). It follows that (rate of work done on the air) ∝ (subglottal pressure)2 ∝ (effective sound pressure)1.2. The exponent 1.2 compares well with the exponent 1.1 found by Lane, Catania, and Stevens for the autophonic response. Experiment 3: Thirty subjects judged the loudness of each word taken from Experiment 1 relative to the reference token in the frame Compare the words: bar and …. It was found that for any one vowel in the middle range, (loudness) ∝ (effective sound pressure)1.2, suggesting that subjects assessed the work done and not the auditory sensation in the usual way as found by Lane, Catania, and Stevens.