[Cardiovascular responses to repeated exposures to intermittent noise. Tentative validation of the law of initial value].

Eighteen female undergraduate subjects were submitted three times to an intermittent 55 min. pink-noise made of 6 x 5 min. periods at 103 dB (A), alternating with 5 x 5 min periods at 40 dB (A). Arterial blood-pressure was measured by the auscultatory method during the last minute before each noise-step (initial value) and during the first minute following it. Concomitant values of heart-rate (continuously recorded) were also taken into account in the same way. Arterial blood pressure as well as heart-rate homeostatic response to both types of noise-steps obey the Law of initial value, respectively in 38 p. 100 and 33 p. 100 of the cases, but the Law fails to reveal adaptive changes in responses from the first to the third exposure to acoustical stress.