The spectral analysis of cough sounds in childhood respiratory illness

Cough is the commonest symptom of childhood respiratory disease and at times may be the predominant feature. The characteristic sound of the cough is often considered by the clinician as a useful diagnostic feature in such conditions as croup and whooping cough. This has prompted a closer study of the physical basis of the cough sounds and their relationship to the pathological processes in the airway.¹ Keleman et al. ² have demonstrated that there are at least three phases to any particular cough, that is, an initial burst due to air turbulence and tissue vibration, followed by a noisy phase, and the final vocalic burst as the glottis forcefully cuts off the air flow. These studies have led to the development of computer assisted methods of evaluation of cough.³ In turn, sound spectral analysis techniques, which have been used extensively to study lung sounds in asthma,⁴ have been applied to cough sounds.^5,6 A microcomputer-based system which allows rapid performance of such analyses has been devised and described recently.⁶