NVIC 12-82: Recommendations on controlling excessive shipboard noise

NVIC 12-82 2 Jun 1982 NAVIGATION AND VESSEL INSPECTION CIRCULAR NO. l2-82 Electronic Version for Distribution Via the World Wide Web Subj: Recommendations On Control of Excessive Noise Ref: (a) 46 CFR 32.40-15 (b) 46 CFR 72.20-5 (c) 46 CFR 92.20-5 (d) International Maritime Organization (IHO) Resolution A.468(XII), "Code On Noise Levels On Board Ships". (e) U.S. Naval Ocean Systems Center, "Study of Airborne Noise On Merchant Ships" (see enclosure (9), reference 1).

Recommendations on Control of Excessive Noise — PURPOSE. This Circular contains the Coast Guard’s recommended guidelines to the U.S.

maritime industry for addressing conditions of high noise. The guidelines were developed in consideration of the need for protecting crewmembers from noise exposures which may produce permanent noise induced hearing loss; for providing crewmembers with suitable conditions for recuperation from the effects of exposure to high noise levels; and for providing a safe working environment by giving consideration to the need for effective speech communication and for hearing audible alarms and warnings. Amplifying information in attached enclosures is provided as guidance in addressing key aspects of noise control.

Recommendations on Control of Excessive Noise — APPLICATION.

a. The recommendations of this Circular apply to all commercial vessels inspected by the Coast Guard except Mobile Offshore Drilling Units. b. Although these guidelines are not directed specifically to uninspected commercial vessels, the Coast Guard considers them to be appropriate guidelines should any owner of uninspected vessels also choose to follow them. c. At the time of this publishing, the Coast Guard is collecting data to determine whether separate guidelines would be appropriate for inspected offshore drilling units and fixed structures. However, in lieu of separate guidelines, these guidelines are recommended for the interim. NAVIGATION AND VESSEL INSPECTION CIRCULAR NO. l2-82

Recommendations on Control of Excessive Noise — DISCUSSION.

a. According to a recent Coast Guard-sponsored study (enclosure (9), ref. 1), noise exposures of certain personnel aboard U.S. merchant vessels were found to be in excess of those considered to be safe. The study also indicated that high noise levels aboard ship interfere with speech intelligibility) internal shipboard communications and the audibility of warning signals, which potentially impairs the safety of some operations on the vessel. Additional studies from foreign countries and information from other sources overwhelmingly support these findings for virtually all classes of commercial vessels. The studies also demonstrate that unlike shoreside workers who can retreat to a quiet environment after their work shift, merchant seamen are part of a mobile environment and may not have the opportunity to retreat to a quieter) relaxed atmosphere. Crew quarters, recreation areas, mess rooms, etc. are sometimes as noisy as the working environment. Similar problems are also widely reported in the offshore drilling industry. (NOTE: At the time of this publishing, the Coast Guard is still conducting a study on the particular noise problems in the offshore drilling industry.) b. The effect of noise on hearing is a function of the actual noise level, its component frequencies and the duration of exposure. An excessive combination of these elements results in a shift in a person’s threshold of hearing, i.e., an elevation in the lowest level of sound detectable to the ear. A threshold shift may be recoverable to varying degrees, depending upon its magnitude, provided the person retreats to a quiet environment

(generally accepted as below 75 db(A)) for a sufficient time.

While small threshold shifts may be totally recovered, large shifts are only partially recoverable leaving with each occurrence a small permanent threshold shift, known as hearing loss.

The minimum goal of a noise control program should be to insure that an exposure (noise level over a certain duration) is not so great that the temporary threshold shift cannot be recovered during the following rest period. c.

After careful study, the Coast Guard has concluded that the most meaningful method of evaluating excessive noise in the maritime industry is by measuring the cumulative noise exposure during the complete 24-hour day.

In addition to consideration of the normal work time noise exposure, the 24-hour exposure measurement considers the time after exposure to high noise to evaluate whether sufficient quiet time is provided to allow for recovery from temporary threshold shift.

The term which will be used to express this measurement is the "24-hour effective exposure level," or L (24), and is defined in technical terms in eff enclosure (1).

The L (24)concept differs somewhat from the criteria proscribed by the eff Occupational Safety and Health Administration (OSHA) because of several factors which distinguish the maritime industry from industry ashore.

However, the L (24) criteria eff would afford similar protection. d.

The exposure limit recommended herein (82 dB(A)) is, like almost all exposure limits, based upon an evaluation of a certain degree of risk to some personnel and does not insure that all personnel will not incur hearing damage.

For this reason a hearing conservation program containing a system for periodic audiometric testing of personnel is necessary to detect those susceptible persons at the initial outset of a hearing impairment before any appreciable damage is accrued.

Since, such a program would generally not be necessary if exposure levels (computed without regard to attenuation contributed by hearing protective devices) were further reduced to 77dB(A), the Circular suggests that new vessels be designed so that the 77dB(A) level may be achieved.

NAVIGATION AND VESSEL INSPECTION CIRCULAR NO. l2-82 e.

The control methods, i.e., engineering controls, administrative controls or hearing protective devices, selected by the owner/operator of a unit to achieve the recommended exposure limits, would depend upon economic and other considerations.

Based upon data obtained from the study conducted by the Coast Guard and the state of the art in present noise control technology, the recommendations could be implemented on most units without retrofitting, principally through the use of hearing protectors.

Other units may additionally need to administratively limit the time of exposure, and/or install soundproof control booths.

Ultimately, however, installation of permanent engineering controls to reduce noise levels is the best means of assuring effective hearing protection.

Although this technology may be young in marine applications (in the United States), the Coast Guard has seen several examples where significant reductions in noise levels in engineering compartments through modest engineering controls were achieved.

The exposure levels in this proposal are such that they may be economically achieved on many vessels by using these engineering controls.

It is encouraged that engineering controls be used whenever economically feasible. f.

In November 1981 the International Maritime Organization (IMO, formerly IMCO) approved a standard on shipboard noise entitled "Code On Noise Levels On Board Ships," which applies basically to new ships of 1600 gross tons or more.

The Coast Guard participated in the development of this Code and endorses its recommendations.

As the preamble to the Code makes clear however, it was not intended that the Code be adopted verbatim by member nations.

Rather, each nation was permitted the flexibility to implement the principles of the Code through a method suited to the maritime industry of that nation.

The Coast Guard believes therefore, that the recommendations in this Circular are a satisfactory implementation of the IMO Code.

(NOTE: The IMO Code contains a section suggesting recommended noise level limits for various types of spaces on a unit.

It is believed that this list offers guidance which would be useful to the designers of U.S. vessels and is therefore incorporated verbatim as an enclosure to this Circular.

These levels are provided primarily as guidelines which might be useful for design specifications for suitable types of new vessels.) g.

It is considered that implementation of the recommendations in this Circular will involve an ongoing process encompassing a time frame of several months to years, depending upon the vessel.

It is anticipated that phases involving measurement, provision of hearing protection devices, installation of some engineering controls, implementation of the hearing conservation program and other administrative aspects could be completed within two years.

However, it may take up to four years before complete engineering solutions can be designed and installed. h.

The limits and procedures set out in these guidelines are regarded as minimum acceptable precautions against high noise conditions.

For a greater margin of safety, owners and operators may wish to provide higher levels of protection.

Also, as technology improves and as more scientific information becomes available, consideration will be given to amending these guidelines accordingly.

Recommendations on Control of Excessive Noise — ACTION.

a. The following paragraphs b through i contain recommended guidelines for protecting crewmembers from conditions of high noise. Additional information in the attached NAVIGATION AND VESSEL INSPECTION CIRCULAR NO. l2-82 enclosures (1) through (9) are provided to amplify certain provisions of the recommendations. Definitions of terms used are contained in enclosure (1). b. Recommended Exposure Limit.

(1) Each crewmember's 24-Hour Effective Exposure Level, L (24), as defined in eff enclosure (1), should be constrained to a maximum of 82 dB(A).

(2) If exposure levels were further reduced, through engineering and administrative controls alone, to an L (24) criteria of 77 dB(A), the hearing conservation eff program outlined below would no longer be necessary in most cases. The Coast Guard believes that the technology to accomplish this objective will be feasible on most deep-sea vessels, over 1600 gross tons, constructed after 1985 and recommends designing to the 77 dB(A) criteria at that time.

(3) NOTE: The exposure limits specified above are based upon the findings that exposures to high noise in the maritime industry are normally intermittent, as defined in enclosure (1). If work shift noise exposure is continuous, vice intermittent, then exposure levels should be reduced even further.

(4) L (24) can be achieved by any combination of engineering controls, eff administrative controls or hearing protective devices. However, because engineering controls provide the most positive means of assuring adequate protection, it is recommended that engineering controls be given first consideration and evaluated for feasibility before opting for other methods. Discussions on engineering controls and hearing protective devices are included in enclosures (4),

(7) and (8).

(5) The Coast Guard realizes that reducing noise levels generally becomes increasingly more difficult on smaller vessels. It was for this reason that the IMO noise level limits referred to in subparagraph c.(2) below were restricted to vessels over 1600 gross tons. On many existing vessels of less than 500 gross tons, the incorporation of effective structural and engineering alterations to attenuate structure-borne noise may be economically prohibitive. However, through the use of hearing protective devices, administrative controls and selective engineering changes, the recommended 24-hour exposure limit, L (24), of 82db(A) should eff still be attainable. c. Recommended Noise Limits.

(1) Where practicable, maximum noise levels in berthing spaces, and in mess spaces of units over 500 gross tons, should be no greater than 75 dB(A) on existing units and 70 dB(A) on new units.

(2) Annex III, paragraph (l)(e), of the International Regulations for Preventing Collisions at Sea, 1972 (commonly called the 72 COLREGS) contains the following requirements: "The sound pressure level of the vessel's [fog whistle] at listening posts shall not exceed 110 dB(A) and so far as practicable should not exceed 100 dB(A)." The 72 COLREGS are U.S. law and are mandatory for all U.S. vessels navigating on the high seas. NAVIGATION AND VESSEL INSPECTION CIRCULAR NO. l2-82

(3) As stated in Discussion paragraph 3.f., the "Code On Noise Levels On Board Ships," a noise standard published in November 1981 by the International Maritime Organization (IMO), contains a listing of suggested noise level limits for various spaces on ship. The Coast Guard considers that these limits would generally be appropriate for adoption as minimum design specifications for ocean- going vessels over 1600 gross tons which would be subject to the IMO Code. This list of limits is in enclosure (6). It is not intended that the list supplant any other recommendation in this paragraph 4., nor is it meant to imply that, if followed, would any exposure limit recommended herein be automatically achieved. d. Rearing Protective Devices.

(1) Unless the L (24) computed or measured for a crewmember accounts for and eff allows such an exposure, crewmembers should be required to wear hearing protective devices whenever entering spaces with noise levels greater than 85 dB(A).

(2) NOTE: Any exposure of persons not wearing hearing protection to noise levels over 105 dB(A) should be avoided. However, if such exposures are unavoidable, they should be constrained to the principle of intermittent exposure (see definition in enclosure (1)) such that each exposure duration is one-seventh of the total allowable exposure at that noise level.

(3) At no time should the unprotected ears of crewmembers be exposed to non- impulse noise levels over 115 dB(A) or to impulse noise levels over 140 dB(A). e. Evaluation of Noise Conditions. An evaluation of noise conditions should be conducted on each unit and the results documented. The evaluation should consider noise conditions during all normal operations underway and in port. Enclosure (3) should be consulted with regards to proper equipment and measurement procedures. f. Warning Notices.

(1) Where the noise level in spaces exceeds 85 dB(A), entrances to such spaces should carry a warning notice advising personnel of the noise hazard and the need for hearing protection. (A guide for design of this sign is the ANSI Specification for Accident Prevention Signs, Z35.l-1972.) If only a minor portion of the space has such noise levels the particular location(s) or equipment should be identified at eye level, visible from each direction of access.

(2) Where hand tools, galley and other portable equipment produce high noise levels in normal working conditions, warning information should be provided, preferably on the device. g. Instruction to Crewmembers.

(1) Crewmembers should be instructed in the hazards of high and long duration noise exposure and the risk of noise induced hearing loss. Instruction should also include NAVIGATION AND VESSEL INSPECTION CIRCULAR NO. l2-82 a description of the unit's noise control program, the types of hearing protection devices provided and their proper use and care, and the unit's hearing conservation program.

(2) Appropriate crewmembers should receive such instruction as is necessary in the correct use and maintenance of machinery and silencers or attenuators in order to avoid the production or transmission of unnecessary noise. h. Hearing Conservation Program.

(1) All crewmembers having 24-Hour Effective Exposure Levels (computed, in this case, without regard to attenuation contributed by hearing protective devices) greater than 77 dB(A) or routinely exposed to noise levels greater than 85 dB(A) should be included in a hearing conservation program as outlined in enclosure (5).

(2) Much of the maritime industry utilizes a highly mobile labor force of which individual personnel work a vessel or rig for a limited period and then move on to another unit. Consequently, it is often impractical for operators of these units to individually implement portions of hearing conservation programs involving audiometric testing and recordkeeping. In such cases it is recommended that a program of audiometric testing be coordinated on a group basis between the owner/operators and the employees. i. Responsibilities.

(1) The owner/operator of a unit should be responsible for ensuring that means for noise reduction and control are applied and maintained according to the recommendations of this Circular. Particular attention should be paid to insuring that the unit's officers are informed of the provisions of the unit's noise control program and the need for instructing crewmembers as provided in paragraph f, and to insuring that hearing protectors are provided and maintained.

(2) Crewmembers should be responsible for complying with the unit's noise control program, as instructed, paying particular attention to wearing provided hearing protectors in the proper manner while working in the prescribed locations. End: (1) Definitions

(2) Determining the Effective Exposure Level (Examples)

(3) Equipment and Measurement

(4) Hearing Protective Devices

(5) Hearing Conservation program

(6) IMO Noise Limits

(7) Suggested Engineering Methods for Controlling Noise

(8) Noise Reduction On Towboats and Other Small Vessels

(9) References