C
-
12
Glossary and Formulas
LxT Manual
p
A
(
) is the A-weighted sound pressure
p
0
is the reference sound pressure of 20 µPa
In the equation, the numerator of the argument of the
logarithm is the root-mean-square, frequency-weighted
sound pressure level over the averaging time interval T.
The format used by the LxT to dis-
play equivalent continuous sound
pressure level is
L
Xeq
, where
X
is the
frequency weighting (
X = A, C or Z
).
When a frequency weighting other than A is used, the
frequency weighting used shall be included explicitly in the
title and the formula of the quantity, for example equivalent
continuous C-weighted sound pressure level:
If no frequency weighting is used, the quantity is simply
called equivalent continuous sound pressure level.
Exchange Rate (Q),
Exchange Rate Factor (q),
Exposure Factor (k)
It is defined in ANSI S1.25 as “the change in sound level
corresponding to a doubling or halving of the duration of a
sound level while a constant percentage of criterion
exposure is maintained.” The rate and the factors are given
in the table below.
Standard
: ANSI S12.19
Far Field
There are two types of far fields: the
acousti
c far field and
the
geometric
far field.
Acoustic Far Field
: The distance from a source of sound is
greater than an acoustic wavelength. In the acoustic far field,
the effect of the type of sound source is negligible. Since the
wavelength varies with frequency (See the definition of
Wavelength), the distance will vary with frequency. To be in
dB
P
d
P
T
L
L
T
t
C
0
2
/
1
2
CeqT
CT
/
1
lg
20
Exchange Rate, Q
Exchange Rate
Factor, q
Exposure Factor, k
3.01
10
1
4
13.333
.75
5
16.667
.60
6.02
20
.50
Summary of Contents for SoundExpert LxT
Page 1: ...LxT Manual for SoundTrack LxT SoundExpert LxT TM...
Page 55: ...4 18 Measurement Settings Tabs LxT Manual...
Page 81: ...5 26 View Spectrum Normalized Optional LxT Manual...
Page 93: ...6 12 Data Storage After Improper Shutdown LxT Manual...
Page 110: ...LxT Manual Certification 7 17...
Page 143: ...11 6 Control Panel Data Explorer LxT Manual...
Page 167: ...12 24 Options LxT Manual...
Page 179: ...14 4 User LxT Manual FIGURE 14 5 shows the User tab FIGURE 14 5 User Tab...
Page 185: ...15 6 File System LxT Manual...
Page 191: ...16 6 Miscellaneous Parameters LxT Manual...
Page 206: ...LxT Manual Technical Specifications A 9 Typical Z Weight Frequency Response...