The Hazards And Costs Of The Workplace Acoustical Environment
The question, "Is the workplace acoustical environment hazardous to your health?", has many implications and different responses depending on your point of view. Yes, noise can kill and cause permanent injury. However, unlike a chemical spill, noise must be extreme in order to kill outright. Sounds and vibrations from a space ship launch could kill outright if one were close enough. However, this situation is rare.
More typically, hazards due to noise are of a secondary nature. Too much noise causes hearing loss, stress and possible deafness. Noise also becomes a killer when it masks the sound of a warning from a fellow worker. Noise mitigation efforts deserve the same concern as other health hazards. Unfortunately, this approach has not been the case in our efforts to improve our environment. While we have many laws about noise levels in the workplace, our legal efforts to enforce them have been fraught with inconsistency, lack of funds and outright misunderstandings.
Most acoustical materials appear benign. However, efficient sound absorbers are typically composed of fibers and open cell foams. Recent allegations that many fibers can cause cancer have raised serious questions by specifiers of building materials, building owners and users. In the case of open cell foams, the issue centers on their flammability and release of toxic fumes. These concerns are real and to ignore them could be costly. By contrast, many have considerable test data to argue the concerns are overblown. What is the answer? Unfortunately, the jury is still out. What is at risk, however, is that ignorance of material performance can produce considerable health risk and litigation.
As with any contentious issue, knowledge, the dissemination of test data, and proper application of the test results to actual situations may be the only safeguard for the building owner, designer, architect, contractor and facilities manager.
Who Regulates Acoustical Issues?
The United States Occupational Safety and Health Administration and the Environmental Protection Agency have strict guidelines on the amount of noise that is acceptable in the workplace. For example, OSHA limits the noise that a worker may be exposed to in an 8 hour work day to 90 dBA. Sound levels over 85 dBA mandate that all workers so exposed shall have audiometric tests conducted annually. Higher noise levels require limited worker exposure (See Figure 1).
OSHA requires one of three techniques to mitigate a noisy workplace: engineering controls that lower the level below 85 dBA; management controls that limit the time a worker may be in a noisy environment; and temporary measures that can be utilized until acceptable engineering or management controls are installed. Note that ear protectors are only a temporary solution.
The EPA regulates noise levels at property lines. These limits vary depending on the type of noise, the type of receiver occupancy and the time of day. Generally, noise that is intrusive such as transportation and factory noise is considered unacceptable. State, local and model building codes have noise ordinances that impact all aspects of our acoustical environment. Criteria can vary widely from community to community.
Acoustics & The ADA
The Americans with Disabilities Act has a section dealing with acoustical criteria including the requirements for Assistive Listening Systems. ALSs are one item in an array of what the ADA calls "auxiliary aids". Various auxiliary aids and other measures may be required for any one facility. ALS requirements apply to assembly areas in which audible communications are integral to the use of the space such as facilities where there is live speech or music (e.g. lecture halls and theatres) or recorded programs (e.g. movie theatres). All public accommodations and commercial facilities designed and occupied after Jan. 26, 1993 require compliance (See Figure 2).
The cost of complying with ADA requirements can vary depending on the original plans for the building. If acoustics was not a part of the original planning, ADA criteria could increase costs by $10 per square foot. Addition of sound absorbing materials, sound barriers and sound amplification systems are the major cost items. A well designed space with good acoustics may only require additional wiring for individual amplifiers for a small portion of the space.
Architectural acoustics deals primarily with the sound quality of a space. In the case of auditoriums, concert halls and public spaces, acoustical designs center on the use of sound absorbing materials to control the reverberation time in the occupied space to provide the desired listening environment. If speech understandability is a key attribute, a low reverberation time, with no echoes is desired. Longer reverberation and focused sounds may be desired for some musical performances where no amplification is utilized.
Containment of noise from a source signal is needed between occupancies in hotels, residences, offices and manufacturing facilities. Sound absorption attributes of materials are measured by the Noise Reduction Class. Barriers between occupied spaces are rated by their ability to block sound and their Sound Transmission Class. Selection of proper acoustical materials and systems of construction is best specified by a qualified acoustician or member of the National Council of Acoustical Consultants. Criteria are established by the user need. Building codes generally provide minimum recommendations.
Open office acoustics is a special field where speech privacy is the key issue. With no barriers of significance, the degree of success in achieving normal or confidential privacy is a balance and compromise whereby all the elements of the acoustical environment act together as a system.
To be effective in acquiring confidential speech privacy, the occupied space must have highly sound absorbent ceilings and vertical surfaces (i.e. walls, columns, windows, etc.), sound barriers that block direct sound and highly sound absorbent faces to reduce reflected sound and a background masking system. New rating systems are Speech Privacy Potential, for an entire working acoustical system, and Articulation Class, for rating individual system components such as a ceiling material, wall treatment and the like. Criteria are primarily based on user needs and should be established by acoustical experts. The bottom line to achieving a successful open office acoustical environment can, and has been measured, in "worker productivity" and "user satisfaction".
Retrofit acoustics are notoriously expensive and may cost five times the expense of an original installation. For this reason, it is very cost-effective to require professional acoustical designs and assure they are properly installed in all new or renovated buildings. In addition, legal remedies can range from court-mandated corrections, building code and/or noise ordinance violations, to, in certain cases, fines up to $100,000.
In the case of rental space such as multi-family dwellings, hotels and offices, poor sound barriers between living units will cause considerable loss in rent and/or sales. Poor office acoustics likewise lowers property values and worker productivity. Auditoriums with bad acoustics are shunned by potential performers causing a loss of revenue.
An extensive family of acoustical standards exist. Most have been prepared by the American Society of Testing and Materials Committee E33 - Environmental Acoustics. Expert volunteers from manufacturers, general interest and users have prepared industry-wide standards for testing and standardizing the acoustical properties of materials and systems of construction, architectural and environmental acoustics, industrial noise control and office acoustics. ASTM Designation E 1433 - "Standard Guide for Selection of Standards on Environmental Acoustics", Annual Book of Standards, Vol. 4.06, contains a detailed list of all the applicable acoustical standards and a description of the method, use, result and summary for each standard. Also, ASTM Committee E33 sponsors a two-day seminar on architectural acoustics each year.
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