Section 149.697 - What are the requirements for a noise level survey?(a) A survey to determine the maximum noise level during normal operations must be conducted in each accommodation space, working space, or other space routinely used by personnel. The recognized methodology used to conduct the survey must be specified in the survey results. Survey results must be kept on the deepwater port or, for an unmanned deepwater port, in the owner's principal office.(b) The noise level must be measured over 12 hours to derive a time weighted average (TWA) using a sound level meter and an A-weighted filter or equivalent device.(c) If the noise level throughout a space is determined to exceed 85 db(A), based on the measurement criteria in paragraph (b) of this section, then signs must be posted with the legend: "Noise Hazard-Hearing Protectors Required." Signs must be posted at eye level at each entrance to the space.(d) If the noise level exceeds 85 db(A) only in a portion of a space, then the sign described in paragraph (c) of this section must be posted within that portion where visible from each direction of access.(e) Working spaces and other areas routinely used by personnel, other than accommodation spaces, must be designed to limit the noise level in those areas so that personnel wearing hearing protectors may hear warning and emergency alarms. If this is not practicable and warning and emergency alarms cannot be heard, visual alarms in addition to the audible alarms must be installed.