Psychoacoustic quantification of mechanical heart valve noise

Mechanical heart valves produce short clicking sounds during closure. These closing sounds are annoying for some patients and their partners by causing sleeping disorders or social embarrassment. Various methods for measuring the sounds have been developed both in vitro and in vivo using calculation of A-weighted sound pressure level or loudness according to ISO 532 B. The study aim was to evaluate the relevance of different psychoacoustic parameters in the evaluation of closing sounds.

Closing sounds were recorded from patients with ATS valves (n = 13), On-X valves (n = 18) and St. Jude Medical heart valve prostheses (n = 16). The sounds were recorded 5 cm above the chest of patients in a supine position, in a sound-insulated chamber. The mean peak values of loudness and sharpness were calculated and used to determine the psychoacoustic annoyance using a modification of the Widmann formula. This was verified by a listening test for ranking closing sounds of different level and sharpness by annoyance.

There was no statistically significant independence between loudness difference or psychoacoustic annoyance difference and agreement among the test persons. For the valves, loudness ranged from 0.07 to 2.57 sone, and the psychoacoustic annoyance from 0.1 to 5.4.

The results of this study showed that both sharpness and loudness have a significant influence on annoyance from closing sounds from mechanical heart valves, and indicated that the substantial variation in the parameters may be due to individual patient physiology.