BACKGROUND: Exposure to noise in a critical care unit may trigger a response by the sympathetic nervous system, thereby increasing cardiovascular work in patients recovering from cardiac surgery. OBJECTIVE: To investigate the effects of a music intervention given twice on the first postoperative day on noise annoyance, heart rate, and arterial blood pressure in subjects with high (n = 22) and low (n = 18) sensitivity to noise. METHODS: A prospective, quasi-experimental, repeated-measures design was used. Based on results of power analysis, the sample size was 40. Subjects were recruited preoperatively, and their sensitivity to noise was assessed. On the first postoperative day, repeated-measures data were collected on levels of noise annoyance and physiological variables during 15 minutes of baseline and 15 minutes of music intervention on two occasions. Subjects completed a follow-up questionnaire regarding their perceptions of the noise in the critical care unit and the music intervention. RESULTS: Repeated-measures analysis of variance showed that subjects had lower levels of noise annoyance during music intervention than at baseline. Heart rate and systolic blood pressure decreased during the music intervention compared with baseline. Diastolic blood pressure decreased during the music intervention from baseline during time 2, but not time 1. Subjects with high baseline scores of noise sensitivity preoperatively had higher baseline levels of noise annoyance in the critical care unit the first postoperative day. Subjects rated the music intervention as highly enjoyable regardless of their baseline noise sensitivity or noise annoyance. CONCLUSION: Results of this study support the idea that noise annoyance is a highly individual phenomenon, influenced by a transaction of personal and environmental factors. Use of a music intervention with cardiac surgery patients during the first postoperative day decreased noise annoyance, heart rate, and systolic blood pressure, regardless of the subject's noise sensitivity.