Spartan 821/721 Manual
Glossary
C-15
FIGURE C-1
The RMS value of any function
y = f(t)
over the range
t = a
to
t = b
can be defined by the
following equation:
Shift Time
Shift Time is the length of time in hours that a dosimeter subject could be exposed to
noise at work. It’s used to calculate Projected LEP, d; P. LEX, 8h; Projected Dose; and
Projected TWA. In the dosimeter Settings, enter the Shift Time at the following locations:
Settings
Dosimeter 1, 2
, or
3
.
Sound
Sound is comprised of rapid oscillatory compression changes in a solid, liquid, or gas
medium that propagate to distant points. It is characterized by changes in density,
pressure, motion, and temperature. Not all rapid changes in the medium are sound
since they do not propagate. Wind noise is an example of this. Sound can also be
characterized as the auditory sensation evoked by the oscillatory changes.
Sound is the physical phenomenon associated with acoustic (small) pressure waves.
Noise is unwanted sound that causes adverse effects in those exposed to it, such as
hearing loss or annoyance. It can also be defined as the sound made by other people. In
every case, choosing the word
noise
involves a judgment of whether the sound is
welcome or not.
Sound Exposure (E)
The total sound energy of the actual sound in a given time interval. For a dosimeter, the
time interval is the record’s Run Time. The units for sound exposure are Pa
2
S (pascal
squared seconds) or Pa
2
H (pascal squared hours).
1
b a
–
----------- y
2
t
d
a
b
E
p
2
t
t
d
T
1
T
2
=
p
(t) = instantaneous, frequency weighted (A or C), sound pressure in pascals
T
2
– T
1
= measurement duration or “Run Time”
