BACKGROUND: Many individuals complain of disturbed sleep during the wintertime when their air conditioner (AC) is off. Therefore, we conducted this study to objectively assess the impact of AC sound on sleep latency, sleep duration, and sleep efficiency. METHODS: An experimental study was conducted on 48 healthy young adults, in their homes, to assess the effect of a standardized AC white noise, on sleep latency, duration, and efficiency, while simultaneously monitoring light intensity and room temperature. The study was conducted during the winter months. Sleep quality was objectively assessed using sleep actigraphy. Participants were monitored for two nights, during which two different, randomized sets of conditions were used: During one of the nights, the adults were exposed to 43 dB AC white noise; during the other night, adults were not exposed to the AC white noise. RESULTS: Actigraphy results showed that the mean sleep duration during the AC sound nights (ASNs) was 466.8 +/- 60.8 min, compared to 478.8 +/- 55.4 min during the non-AC sound nights (NASNs) (P = 0.6). Sleep-onset latency was 10.8 +/- 15.2 min and 15.1 +/- 18.2 min during the ASNs and the NASNs, respectively (P = 0.8). Moreover, there was no difference in sleep efficiency, 81% +/- 7.8% vs. 78.8% +/- 15.4% in the ASNs and NASNs, respectively (P = 0.9). CONCLUSION: AC sound had no significant positive effect on sleep duration, latency, and efficiency.