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Aircraft Engines Noise
Noise is one of the most serious constraints on expanding and improving the international air transport system. Greater air traffic and larger population growth in areas surrounding airports are increasing the impact of aircraft noise on the community.
Turbofan engine fan noise is one of the largest noise contributors, along with jet noise radiated by aircraft at take-off. The fan generates noise at its inlet similar to the noise caused by a propeller. The air swirls as it exits the fan. The swirling causes a loss of momentum, so the air is straightened out by running it through a set of stationary vanes called stators at the fan outlet to maintain momentum. The impact of the air on the stator blades is another major source of noise.
Methods of suppressing noise
Noise suppression of internal sources is approached in two ways; by basic design to minimize noise originating within or propagating from the engine, and by the use of acoustically absorbent linings. Noise can be minimized by reducing airflow disruption which causes turbulence. This is achieved by using minimal rotational and airflow velocities and reducing the wake intensity by appropriate spacing between the blades and vanes. The ratio between the number of rotating blades and stationary vanes can also be advantageously employed to contain noise within the engine.
Noise is one of the most serious possible hazards or infections to human
Staffs are at risk for noise-induced hearing loss. Although hearing loss may not be symptomatic, the first complication and the reason for seeking a hearing evaluation may be tinnitus.
Noise is always present during the work of staff divided into distracting noise and destructive noise. This division results from the variety of parameters determining sound hazards and their influence on the human organism.
The sources of Aircraft Engines sounds inducing hearing loss that can be diminished are high-speed Turbofan engine fan noise, high-velocity suction,
Occupational Exposure to Noise
Application of OSHA’s General Industry Standard for Occupational Exposure to Noise
(29 CFR §1910.95) to Employees on Aircraft in Operation (other than flight deck crew).
1. OSHA Regulations. Provisions and requirements of OSHA’s occupational noise exposure standard.
What does the occupational noise exposure standard require and what must an employer do to comply with the provisions of the standard?
The following discussion is a general overview of the standard’s requirements that likely could be most pertinent to employees working on an aircraft in operation (other than flight deck crewmembers). This discussion is not intended to modify, supplement, or replace the requirements specifically listed in the standard. See29 CFR §1910.95.
OSHA’s noise standard requires that employers take certain precautions against the effects of noise exposure when sound levels meet or exceed the standard’s permissible noise exposure levels. The standard applies to varying noise levels and to exposures of less than8 hours. (For example, a90-decibel exposure over8 hours is a permissible noise exposure, but a115-decibel exposure is permissible only for1/4 hour or less.) When employees are subjected to sound levels exceeding permissible noise levels set forth in the standard, the employer must implement administrative or engineering controls. If such controls fail, the employer must provide and the employees must use personal protective equipment (PPE). However, when exposures exceed or equal the8-hour time-weighted average of85 decibels or a dose of50 percent (referred to as the “action level”), the employer must take other actions as follows: monitor sound levels, administer a hearing conservation program, provide hearing PPE at no cost to employees (the employees must have a variety of hearing PPE from which to choose), notify each employee exposed above the action level, and establish and maintain an audiometric testing program.
The employer shall provide training in the use and care of all hearing protectors provided to the employees, shall ensure proper initial fitting, supervise the correct use of all hearing protectors, and evaluate the hearing protector attenuation. The audiometric testing program must not incur a cost to employees and must be performed by licensed or certified audiologists or other professionals. A baseline audiogram must be taken within6 months of the employee’s first exposure with annual audiograms thereafter. The audiograms must be evaluated to detect a
Standard Threshold Shift (STS), which is a change in hearing threshold relative to the baseline audiogram (of an average of10dB or more at the2000,3000, and4000 Hz in either ear).
Employees with STSs shall be offered follow-up treatment.
The employer’s noise monitoring program must include personal sampling to account for any high worker mobility, significant variations in sound level, or significant components of impulse noise. The employer must repeat the monitoring when there is a change in production, process, or equipment. Employees or their representatives may observe the monitoring.
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The employer shall institute a training program and shall ensure employee participation.
Training shall be repeated annually and shall include the topics of the effects of noise on hearing, the purpose of the hearing protectors, the advantages, disadvantages and the attenuation of the various types of hearing protectors and instructions on their selection, fitting, use and care. The employer shall make available to affected employees or their representatives' copies of the noise standard and the employer shall post a copy in the work place. The employer shall maintain all employee test records and exposure assessment records.
