Novel long-term cardiovascular effects of industrial noise.

Baboon subjects were instrumented with indwelling arterial catheters for continuous measurement of blood pressure and heart rate before, during, and after exposure to industrial noise eight hours daily. Initial exposure to noise produced transient, acute elevations of systolic and diastolic blood pressures and heart rates at noise onset, which habituated over the course of noise exposure. Chronic exposure to noise lowered blood pressure and heart rate not only during noise, but particularly after daily noise offset. Blood pressures returned toward baseline after noise exposure was terminated. Plasma catecholamines were also decreased during noise exposure. A control animal which received only masking noise did not demonstrate decreases in cardiovascular parameters. The possibility of classically conditioned associations of noise onset with feeding was discussed.