Patient safety in the Operating Room (OR) depends on unobstructed team communication. Yet the typical OR is loud, containing numerous sounds from surgical machinery overlayed with human-caused sounds. Our objective was to compare machine vs human-caused sounds for their loudness and distraction, and potential impact on team communication. After surveying OR staff about sounds that interfere with job performance and team communication, we recorded 19 machine and 48 human-caused sounds measuring their acoustical intensity. We compared peak measures of machine vs human-caused sound loudness, using Student's t-test. We observed the effect of these sounds on OR staff in 59 live surgeries, rating level of interference with team function. We visually depicted competing sounds through a spectral analysis. The survey response rate was 62.8%. 93% of respondents indicated that OR noise, especially human-caused sounds such as irrelevant conversations, interfere with team communication, hearing, and focus. OR peak decibel levels ranged from 56.8dB (surgical packaging) to 105.0dB (kicked metal stepstool). Human-caused sounds were comparable to machine-caused sounds in terms of mean peak dB levels (77.0 versus 73.8dB, p = 0.32), yet were rated as more interfering with surgical team function. The spectral analysis illustrated both machine and human-caused sound sources obscuring the surgeon's instructions. Avoidable human-caused sounds are a major source of disruption in the OR and interfere with communication and job performance. We recommend surgical team training to minimize these distractions.