1.4 Definitions

 For the purpose of the Code the following definitions apply. Additional definitions are given elsewhere in the Code.

  1.4.1 Accommodation spaces: Cabins, offices (for carrying out ship's business), hospitals, messrooms, recreation rooms (such as lounges, smoke rooms, cinemas, gymnasiums, libraries and hobbies and games rooms) and open recreation areas to be used by seafarers.

  1.4.2 Apparent weighted sound reduction index R'_w : A single number value expressed in decibels (dB) which describes the overall sound insulation performance in situ of walls, doors or floors provides (see ISO 717-1:1996 as amended by 1:2006).

  1.4.3 A-weighted equivalent continuous sound level L_Aeq(T) : A-weighted sound pressure level of a continuous steady sound that, within a measurement time interval, T, has the same mean square sound pressure as a sound under consideration which varies with time. It is expressed in decibels A (dB(A)) and is given by the following equation:

  1.4.4 A-weighted sound pressure level or noise level: The quantity measured by a sound level meter in which the frequency response is weighted according to the A-weighting curve (see IEC 61672-1).

  1.4.5 C-weighted equivalent continuous sound level L_Ceq(T) : C-weighted sound pressure level of a continuous steady sound that within a measurement time interval, T, has the same mean square sound pressure as a sound under consideration which varies with time. It is expressed in decibels C (dB(C)) and is given by the following equation:

  1.4.6 C-weighted peak sound level L_Cpeak: C-weighted maximum instantaneous sound pressure level. It is expressed in decibels C (dB(C)) and is given by the following equation:

  1.4.7 C-weighted sound pressure level or noise level: The quantity measured by a sound level meter in which the frequency response is weighted according to the C-weighting curve (see IEC 61672-1 (2002-05)).

  1.4.8 Continuously manned spaces: Spaces in which the continuous or prolonged presence of seafarers is necessary for normal operational periods.

  1.4.9 Crane barge: A vessel with permanently installed cranes designed principally for lifting operations.

  1.4.10 Daily noise exposure level (L_ex,24h) represents the equivalent noise exposure level for a period of 24 hours.

where:

• T is the effective duration on board
• T₀ is the reference duration 24 h.

 The total equivalent continuous A-weighted sound pressure level (L_Aeq T), shall be calculated by using the different noise levels (L_Aeq, T_i) and associated time periods with the following equation:

where:

• L_{Aeq, Ti} is the equivalent continuous A-weighted sound pressure level, in decibels, averaged over time interval T_i ;

  1.4.11 Dredger: A vessel undertaking operations to excavate bottom sediment, where the vessel has permanently installed excavation equipment.

  1.4.12 Duty stations: Those spaces in which the main navigating equipment, the ship's radio or the emergency source of power are located or where the fire recording or fire control equipment is centralized and also those spaces used for galleys, main pantries, stores (except isolated pantries and lockers), mail and specie rooms, workshops other than those forming part of the machinery spaces and similar such spaces.

  1.4.13 Dynamically supported craft: A craft which is operable on or above water and which has characteristics different from those of conventional displacement ships. Within the aforementioned generality, a craft which complies with either of the following characteristics:

• .1 the weight, or a significant part thereof, is balanced in one mode of operation by other than hydrostatic forces;

• .2 the craft is able to operate at speeds such that the function is equal to or greater than 0.9, where "v" is the maximum speed, "L" is the water-line length and "g" is the acceleration due to gravity, all in consistent units.

  1.4.14 Existing ship: A ship which is not a new ship.

  1.4.15 Fishing vessel: A vessel used commercially for catching fish, whales, seals, walrus or other living resources of the sea.

  1.4.16 Hearing loss: Hearing loss is evaluated in relation to a reference auditory threshold defined conventionally in ISO Standard 389-1(1998). The hearing loss corresponds to the difference between the auditory threshold of the subject being examined and the reference auditory threshold.

  1.4.17 Hearing protector: A device worn to reduce the level of noise reaching the ears. Passive noise-cancelling headsets block noise from reaching the ear. Active noise-cancelling headphones generate a signal that cancels out the ambient noise within the headphone.

  1.4.18 Integrating sound level meter: A sound level meter designed or adapted to measure the level of the mean squared time averaged A-weighted and C-weighted sound pressure.

  1.4.19 Machinery spaces: Any space which contains steam or internal-combustion machinery, pumps, air compressors, boilers, oil fuel units, major electrical machinery, oil filling stations, thrusters, refrigerating, stabilizing, steering gear, ventilation and air conditioning machinery, etc., and trunks to such spaces.

  1.4.20 Mobile offshore drilling unit: A vessel capable of engaging in drilling operations for the exploration for, or exploitation of, resources beneath the seabed, such as liquid or gaseous hydrocarbons, sulphur or salt.

  1.4.21 Navigating bridge wings: Those parts of the ship's navigating bridge extending towards the ship's sides.

  1.4.22 New ship: means a ship to which this Code applies in accordance with SOLAS regulation II-1/3-12.1.

  1.4.23 Noise: For the purpose of the Code all sound which can result in hearing impairment, or which can be harmful to health or be otherwise dangerous or disruptive.

  1.4.24 Noise induced hearing loss: A hearing loss, originating in the nerve cells within the cochlea, attributable to the effects of sound.

  1.4.25 Noise level: See A-weighted sound pressure level (paragraph 1.4.4).

  1.4.26 Occasional exposures: Those exposures typically occurring once per week, or less frequently.

  1.4.27 Pile driving vessel: A vessel undertaking operations to install pilings in the seabed.

  1.4.28 Pipe-laying barge: A vessel specifically constructed for, or used in conjunction with, operations associated with the laying of submarine pipelines.

  1.4.29 Port condition: The condition in which all machinery solely required for propulsion is stopped.

  1.4.30 Potentially hazardous noise levels: Those levels at and above which persons exposed to them without protection are at risk of sustaining a noise induced hearing loss.

  1.4.31 Repairs, alterations and modifications of a major character: means a conversion of a ship which substantially alters the dimensions, carrying capacity or engine power of the ship, which change type of the ship, which otherwise so alters the ship that, if it were a new ship, it would become subject to the relevant provisions.

  1.4.32 Sound: Energy that is transmitted by pressure waves in air or other materials and is the objective cause of the sensation of hearing.

  1.4.33 Sound pressure level L_p or SPL : Sound pressure level expressed in decibel (dB), of a sound or noise given by the following equation:

  1.4.34 Voyages of short duration: Voyages where the ship is not generally underway for periods long enough for seafarers to require sleep, or long off-duty periods, during the voyages.

  1.4.35 Weighted sound reduction index, R_w: A single number value expressed in decibels (dB) which describes the overall sound insulation performance (in laboratory) of walls, doors or floors provides (see ISO 717-1:1997 as amended by 1:2006).