A STUDY OF THE MECHANISMS OF NORMAL VOICE MATURATION IN PUBERTAL BOYS

Abstract

Breaking of the voice is one of the obvious outcomes of puberty in boys, which for choristers and choirmasters may be an unwelcome event. The process is said to be complete by age 15.5yr on average but its precise timing in relation lo pubertal stage and the mechanics involved are poorly documented. This phenomenon was investigated in 26 boys, aged 13.4 - 14.3 yr at outset, who have been studied at ihrcc-monihly intervals for 12 months so far. At each visit height, weight, genital and pubic hair (PH) stages were recorded and the mean daily saliva testosterone (T) level calculated from 3 samples collected over the preceding 24-hours. Vocal cord length (VCL) was measured by a novel ultrasound technique, fundamental speaking voice frequency (VF) derived from laryngography and stroboscopy of the vocal cords was performed. All measurements were made by a maximum of two observers for each parameter without reference to previous data. Each pubertal stage was represented in this cohort with normal progression into or through puberty in all but one boy who remained at stage 1 throughout. VCL and saliva T remained unchanged until a significant increase at stage 3 and at each subsequent pubertal stage (p <0.001 throughout). VF, which was inversely proportional to VCL, did not fall significantly until stage 4 when there was a marked decrease (p<0.001) with a further significant fall in stage 5 towards the adult male VF of 120Hz. This suggests that a critical VCL and T concentration is required to initiate voice breaking, although other mechanisms such as cord thickness and motility are also probably involved. In relation to PH development, VF fell significantly in stage 3 (p<0.001) reflecting the known lag in PH compared with genital development. Testicular volume was a poor predictor of VF and saliva T concentrations. These observational data provide more information about the biology of puberty and confirm voice breaking as a late and rather sudden event. Predicting the impending fall of VF by simple genital staging may prove invaluable to the organisation of choirschools.