Answer to Question 1
Typical engineering controls involve:
Reducing noise at the source (e.g., installing a muffler)
Interrupting the noise path (e.g., erecting acoustical enclosures and barriers)
Reducing reverberation (e.g., installing sound-absorbing material)
Reducing structure-borne vibration (e.g., installing vibration mounts and providing proper lubrication)
Answer to Question 2
A number of different factors affect the risk of hearing loss associated with exposure to excessive noise. The most important of these are:
Intensity of the noise (sound pressure level)
Type of noise (wide band, narrow band, or impulse)
Duration of daily exposure
Total duration of exposure (number of years)
Age of the individual
Coexisting hearing disease
Nature of environment in which exposure occurs
Distance of the individual from the source of the noise
Position of the ears relative to the sound waves
