Influence of intense sound stimuli on skin microcirculation.

Sound influences not only the organ of hearing but also other systems including the circulation. The purpose of the present study was to investigate the effect of strong sound on the skin microcirculation of the palmar area of the hand and of the plantar area of the foot, which are areas of dense microvasculature and rich sympathetic innervation. The laser Doppler technique was used for measuring cutaneous red cell flux (RCF). Eighteen normal subjects were studied. The results indicate that a pure tone sound of 1500 Hz, with an intensity of 100 dBA and duration 5 s, applied by earphones caused a significant decrease in RCF in 14 out of 18 subjects in the finger but not in the foot skin. A higher intensity (110 dBA) tone caused a stronger decrease of RCF in the finger. The latency and the duration of the reaction showed a dependence on the intensity of the sound, i.e. the reaction to the stronger stimulus was of shorter latency (p < 0.01) and longer duration (p < 0.05). The duration of the reaction did not show significant change when a longer stimulus of 30 s was applied. Repetitive stimuli evoked habituation (p < 0.05).