On the basis of several Laboratory studies, a three‐band preferred‐frequency speech interference level (PSIL.) of 64 dB (based on the octaves centered at 500, 1000, and 2000 Hz), or an A‐weighted level (LA) of 71 dB, were proposed as the criteria levels for acceptable voice communications. Two validation surveys were undertaken where ambient noise levels were measured and subjective questionnaires were completed in various ship's spaces. When asked to rate a space along a five‐point scale of noisiness (very quiet, quiet, moderately noisy, very noisy, and intolerably noisy), responses tended to center on moderately noisy regardless of objective noise level (PSIL, LA, PNL, LL), confirming the remark, “You get used to it.” When asked to give binary judgment on whether (1) normal speech was affected, (2) work was affected, (3) the space was acceptable, or (4) the environment was loud (and/or noisy, and/or annoying), vice very loud (and/or very noisy, and/or very annoying), the following results were obtained: 80% thought that neither speech nor work was affected (and the space was acceptable) at PSIL of 67 dB (68 dB) or 73 dBA (74 dBA); 20% would accept higher noise levels, but 20% also said levels this high did affect speech and work and made the space “uncomfortable” and the noise “loud.”

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