b. Over exposure to high frequency noise causes more significant hearing loss
than over exposure to low frequency noise of the same intensity. During initial
exposure, most of the hearing impairment is in the frequency range above those
important to the understanding of speech. As a result, early damage is frequently not
noticed by the individual. Detection of losses in these ranges by the medical officer is
important, as early losses may be regarded as danger signs of further potential hearing
loss. Continued exposure will lead to progressively greater damage, including loss of
the speech frequencies that, if allowed to reach an advanced stage, will cause a severe
handicap.
c. Other physiological effects that can be produced by excessive exposure to
noise include nausea and headaches. In many cases the reflex responses of the
individual will be affected.
d. Psychological stress from noise may be manifested in the form of fatigue,
inability to function, annoyance, and distraction.
3-7.
FACTORS DETERMINING THE DEGREE OF NOISE HAZARD
Of the properties or characteristics of noise, there are four that determine
whether a given noise is likely to be hazardous to the hearing of workers.
a. Frequency. The frequency of a noise determines its pitch, which is that
attribute of an auditory sensation in terms of which sounds may be ordered on a scale
extending from low to high. High frequency (high pitched) noises are more dangerous
to hearing than low frequency (low pitched) noises.
b. Intensity. The relative loudness of the noise, expressed in decibels, will play
a large part in determining the degree of hazard; the louder the noise, the greater its
potential for causing hearing loss.
c. The Nature of the Noise. Noise may be continuous or intermittent. It may
be steady or made up of a series of impact or impulse noises.
d. The Duration of Exposure. The longer the exposure, the greater the
damage to the hearing mechanism.
3-8.
ESSENTIALS OF A HEARING CONSERVATION PROGRAM
A hearing conservation program is an effective program to prevent hearing loss
due to exposure to excessive job-related noise. It involves the carefully coordinated
application of engineering control measures, personal protective measures, medical
control measures, health education, proper supervision, and personal discipline on the
part of workers. Normally, the first step in establishing a hearing conservation program
will be to conduct a noise survey. However, there are occasions when a program can
MD0165
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