## 3 International Regulations on Ship Noise
### The IMO Noise Code  
The enactment of the noise code (Resolution MSC.337 (91)) on 1 July 2014, in accordance with SOLAS regulation II-1/3-12, serves to regulate onboard noise. The noise code applies to ships with a gross tonnage (GT) of 1600 tons or more, with certain exceptions for 11 types of ships such as high-speed ships, fishing ships, recreational ships not used for commercial purposes, warships, and ships employing non-propeller propulsion methods. Its objective is to provide a safe working environment and ensure comfortable rest for ship personnel. The noise code outlines a methodology for measuring noise levels inside a ship, including specifications for measurement locations, procedures during testing, considerations for weather conditions, evaluation of noise exposure. In addition to that, it regulates provisions for hearing protection, and display of noise zone warnings and provides clear explanations of various noise-related terms such as hearing loss and hearing protection. The standard for noise in a seafare's private bedroom is regulated in the noise code as 60 dB for ships of more than 1600 tons and less than 10,000 tons, and 55 dB for ships of 10,000 tons and above. The requirement for the sound reduction index between compartments has also been enhanced, and standards for certain areas have been newly established. The noise standards were differentiated before and after 10,000 GT, and the noise standard for residential areas has been reinforced by 5 dB. The sound insulation performance requirement between compartments has been enhanced by 5 dB, and there are requirements between corridors and cabins. IMO sets limits on accessibility based on noise levels to safeguard crew members, as depicted in Figure 1 [58]. Noise levels are categorized into five zones: Zones A to E. According to this standard, the use of hearing protection equipment may be necessary, or the duration of work may be restricted. Currently, the IMO specifies that working without protective equipment is  
Figure 1: Allowable Daily and Occasional Noise Exposure Zone in Ship. allowed in areas with noise levels below 85 dB, such as Zone E. However, it is prohibited to work for more than 8 h out of a 24 h period when exposed to noise of 80 dB or higher. In Zone C, which corresponds to prolonged exposure to continuous noise and periodic work, it is mandatory to wear hearing protection equipment even when exposed to noise below 85 dB for more than 8 h. This requirement is based on research indicating that workers exposed to chronic noise are susceptible to various health issues, including high blood pressure, heart disease, and hearing loss. Irrespective of the duration of noise exposure, in zones like Zone D, where exposure to noise levels of 85 dB or higher occurs, it is mandatory to wear appropriate equipment with a minimum noise attenuation capability of 25 dB. Additionally, in Zone D, when exposed to noise levels of 110-120 dB, hearing protection equipment with a noise attenuation capability of 25-35 dB is required. Access to Zone A, where noise levels exceed 120 dB, is strictly prohibited, and for noise levels above 105 dB, a separate standard for the duration of noise exposure is provided. The hazard zones (Zones A, B, C, and D) are designed to be easily identifiable for crew members entering these areas. Recognition is established by clearly labeling the designated areas of the vessel with appropriate text and markings. According to IMO guidelines, noise levels above 80 dB are classified into four categories: 80-85 dB, 85-110 dB, 110-115 dB, and >115 dB, each indicating a hazardous area. Wearing hearing protection is recommended for noise levels ranging from 80 to 85 dB, and the entrance to such a noise zone is marked with the phrase \"High Noise Level Use Hearing Protectors\". Mandatory hearing protection is required for noise levels between 85 and 110 dB. The entrance to these areas is marked with the phrase \"Dangerous Noise Use of Hearing Protectors Mandatory\".