Relationship Between Subglottal Pressure and Sound Pressure Level in Untrained Voices

SummaryObjectivesSubglottal pressure (Ps) is strongly correlated with sound pressure level (SPL) and is easy to measure by means of commonly available equipment. The SPL/Ps ratio is strongly dependent on the efficiency of the phonatory apparatus and should be of great relevance to clinical practice. However, published normative data are still missing.MethodThe subjects produced sequences of the syllable [pæ], and Ps was measured as the oral pressure during the [p] occlusion. The Ps to SPL relationship was determined at four pitches produced by 16 female and 15 male healthy voices and analyzed by means of regression analysis. Average correlation between Ps and SPL, average SPL produced with a Ps of 10 cm H2O, and average SPL increase produced by a doubling of Ps were calculated for the female and for the male subjects. The significance of sex and pitch conditions was analyzed by means of analysis of variance (ANOVA).ResultsPitch was found to be an insignificant condition. The average correlation between Ps and SPL was 0.83 and did not differ significantly between the female and male subjects. In female and male subjects, Ps = 10 cm H2O produced 78.1 dB and 80.0 dB SPL at 0.3 m, and a doubling of Ps generated 11.1 dB and 9.3 dB increase of SPL. Both these gender differences were statistically significant.ConclusionsThe relationship between Ps and SPL can be reliably established from series of repetitions of the syllable [pæ] produced with a continuously changing degree of vocal loudness. Male subjects produce slightly higher SPL for a given pressure than female subjects but gain less for a doubling of Ps. As these relationships appear to be affected by phonation type, it seems possible that in the future, the method can be used for documenting degree of phonatory hypofunction and hyperfunction.