Tremetrics RA660, Operation Manual

Page: 75 / 79

RA660 Operation Manual
8509790 Rev. 2 73 18/04/2018
H
h Hour
Hrs Hours
Harmonic Any whole number
multiple of the fundamental frequency
of a complex wave. The fundamental
frequency equals the first harmonic.
Harmonic distortion A high-
frequency disturbance that appears as
distortion of the fundamental sine wave.
Hearing The subjective response
to sound and the nervous and cerebral
operations which translate the physical
stimuli into meaningful signals.
Hearing thresholdlevel (HTL ) Amount
(in decibels) by which the threshold of
audibility for that ear exceeds a
standard
audiometric threshold.
The number of decibels above an
average normal threshold for a given
signal. The hearing level dial of an
audiometer is calibrated in dB HTL.
Hearing loss Any loss of sound
sensitivity, partial or complete,
produced by abnormality anywhere in
the auditory system. An increase in the
threshold of audibility, at specific
frequencies, as the result of normal
aging, disease, or injury to the hearing
organs. It is the symptom of reduced
auditory sensitivity, synonymous with
auditory impairment, when a specific
cause can be ascribed. Also used, in a
general sense, to describe the process
of losing auditory sensitivity.
Types of hearing loss are as follows:
Conductive.
A hearing loss originating in the
conductive mechanism of the ear.
Sensori-Neural.
A hearing loss originating in the cochlea
or the fibers of the auditory nerve.
Formerly called perceptive deafness.
Noise Induced.
A sensor neural hearing loss
attributable to the effects of noise.
Hertz (Hz ) Synonymous term for
cycles per second. Most standardizing
agencies have adopted Hertz as the
preferred unit of frequency.
High-frequency loss Usually
showing a hearing impairment, starting
with 2000
Hz and beyond.
Hughson Westlake A proven
methodology using -10 dB and +5 dB
steps to obtain the HTL (hearing
threshold levels).
Hz Hertz (cycles per second) refers
to measuring pitch. Most sounds fall
into the “speech range” of about 300 Hz
to 3000 Hz.
I
Impedance The opposition to sound
wave transmission. It is comprised of
frictional resistance, mass, and stiffness
and is influenced by frequency.
Intensity The power transmitted
along a sound wave. The sound
intensity measured in a specified
direction at a point is the average rate
at which sound energy is transmitted
through a unit area perpendicular to the
specified
direction at the point
considered. Only in plane or spherical
free progressive sound waves is the
intensity
related to the average
pressure p by the equation I=p²/p
c
where p
c
represents the characteristic
impedance of air. In general, however,
there is no simple relation between
sound pressure level and intensity level.
I/O Input / Output
K
k
“Kilo” = (10
3
) =1000
kHz 1000 Hz