Basic Calculations for Occupational Safety and Environmental Health Professionals - Mathematics and Statistics for the Environment - page 422

Hazardous task inventory —A concept based on using work tasks as the central organizing
principle for collecting descriptive information on a given work hazard. It consists of a
list(s) of specific tasks linked to a database containing the prominent characteristics rel-
evant to the hazard(s) of interest which are associated with each task.
Hearing conservation record— Employee's audiometric record, which includes name, age,
job classification, TWA exposure, date of audiogram, and name of audiometric technician.
It is to be retained for duration of employment for OSHA and is kept indefinitely for work-
ers' compensation.
Hearing damage risk criteria —A standard which defines the percentage of a given popula-
tion expected to incur a specified hearing loss as a function of exposure to a given noise
exposure.
Hearing handicap —A specified amount of permanent hearing loss usually averaged across
several frequencies which negatively impacts employment and/or social activities.
Handicap is often related to an impaired ability to communicate. The degree of handicap
will also be related to whether the hearing loss is in one or both ears, and whether the bet-
ter ear has normal or impartial hearing.
Hearing loss —Often characterized by the area of the auditory system responsible for the loss.
For example, when injury or a medical condition affects the outer ear or middle ear (i.e.,
from the pinna, ear canal, and ear drum to the cavity behind the ear drum—which includes
the ossicles) the resulting hearing loss is referred to as a conductive loss. When an injury or
medical condition affects the inner ear or the auditory nerve that connects the inner ear to
the brain (i.e., the cochlea and the VIII cranial nerve) the resulting hearing loss is referred
to as a sensorineural loss. Thus, a welder's spark which damaged the ear drum would
cause a conductive hearing loss. Because noise can damage the tiny hair cells located in
the cochlea, it causes a sensorineural hearing loss.
Hearing loss prevention program audit —An assessment performed prior to putting a hear-
ing loss prevention program into place or before changing an existing program. The audit
should be a top-down analysis of the strengths and weaknesses of each aspect of the
program.
Hearing threshold level (HTL) —The hearing level, above a reference value, at which a speci-
fied sound or tone is heard by an ear in a specified fraction of the trials. Hearing threshold
levels have been established so that a 0-dB HTL reflects the best hearing of a group of
persons.
Hz (Hertz)—The unit of measurement for audio frequencies. The frequency range for human
hearing lies between 20 Hz and approximately 20,000 Hz. The sensitivity of the human ear
drops off sharply below about 500 Hz and above 4,000 Hz.
Impulsive noise —Used to generally characterize impact or impulse noise which is typified by
a sound which rapidly rises to a sharp peak and then quickly fades. The sound may or may
not have a “ringing” quality (such as a striking a hammer on a metal plate or a gunshot in
a reverberant room). Impulsive noise may be repetitive, or may be a single event (as with a
sonic boom). If impulses occurring in very rapid succession (such as with some jack ham-
mers), the noise would not be described as impulsive.
Loudness —The subjective attribute of a sound by which it would be characterized along a
continuum from soft to loud. Although this is a subjective attribute, it depends primarily
upon sound pressure level, and to a lesser extent, the frequency characteristics and duration
of the sound.
Material hearing impairment —As defined by OSHA, a material hearing impairment is an
average hearing threshold level of 25 dB HTL as the frequencies of 1000, 2000, and 3000
Hz.
Medical pathology— A disorder or disease. For purposes of this program, a condition or dis-
ease affecting the ear, which a physician specialist should treat.