RA660 Operation Manual
8509790 Rev. 2
72
18/04/2018
performed on the OSCAR. When the
test completes the results of the test are
compared with the saved baseline for
the OSCAR. If the results of the test are
within acceptable limits (5 dB or less)
the daily biological passes. If the test is
not within acceptable limits (more than
5 dB) the daily biological fails, which
may indicate that the audiometer may
need calibration.
Decibel (dB)
A unit for measuring the
loudness
or
intensity
of
sound.
Decibel expresses the ratio between
two sound pressures or two sound
powers. One-tenth of a bel. Known also
as a non dimensional unit used to
express sound levels. It is a logarithmic
expression of the ratio of a measured
quantity to a reference quantity.
In audiometry, a level of zero dB HL
(decibel
hearing
loss)
represents
roughly the weakest sound that can be
heard by a person with good hearing.
The decibel is a unit of level when the
base of the logarithm is the tenth root of
ten, and the quantities concerned are
proportional to power. Examples of
quantities that qualify are power (any
form), sound pressure squared, particle
velocity squared, sound intensity,
sound energy density, voltage squared.
Thus the decibel is a unit of sound
pressure-squared level; it is common
practice, however, to shorten this to
sound pressure level because ordinarily
no ambiguity results from so doing. The
decibel is one tenth of a bel.
DC
Direct Current
Dosimeter
A device worn on the
person for determining the accumulated
sound exposure with regard to level and
time.
DS
Data System
Dynamic range
That
region
of
measurement of an instrument or
system between the noise floor and
maximum permissible distortion point.
E
Earphone
An
electroacoustic
transducer intended to be closely
coupled acoustically to the ear. The
term receiver should be avoided when
there is a risk of ambiguity.
EMC
Electromagnetic compatibility
Excitation
Stimulus. An external
force (or other input) applied to a
system that causes the system to
respond in some way.
F
°F
Degrees Fahrenheit
Filter
A
device
for
separating
components of a signal on the basis of
frequency.
It allows components in one or more
frequency bands to pass relatively
unattenuated, and it greatly attenuates
components in other frequency bands.
A wave filter is a transducer for
separating waves on the basis of their
frequency. It introduces relatively small
insertion loss to waves of one or more
insertion loss to waves of other
frequencies.
Frequency
The number of complete
oscillations of a vibrating body per unit
of time. In acoustics the unit of
measurement is cps or Hz. The time
rate of repetition of a periodic
phenomenon. The frequency is the
reciprocal of the period. In sound (as in
electricity) the unit of measurement for
frequency is the Hertz (Hz) which
equals one complete waveform (cycle)
per second.
Fundamental frequency
The lowest
frequency of vibration in a complex
wave.
G
GND
electrical ground
Summary of Contents for RA660
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