793
Federal Aviation Administration, DOT
Pt. 36, App. A
Symbol Unit
Meaning
F (i, k) ..........
dB ................
Delta-dB.
The difference be-
tween the original sound
pressure level and the final
background sound pressure
level in the i-th one-third
octave band at the k-th in-
terval of time. In this case,
background sound pressure
level means the broadband
noise level that would be
present in the one-third oc-
tave band in the absence of
the tone.
h ...................
dB ................
dB-down.
The value to be
subtracted from PNLTM
that defines the duration of
the noise.
H ..................
Percent ........
Relative humidity.
The ambi-
ent atmospheric relative hu-
midity.
i ....................
.....................
Frequency band index.
The
numerical indicator that de-
notes any one of the 24
one-third octave bands with
geometrical mean fre-
quencies from 50 to 10,000
Hz.
k ...................
.....................
Time increment index.
The
numerical indicator that de-
notes the number of equal
time increments that have
elapsed from a reference
zero.
Log ...............
.....................
Logarithm to the base 10.
log n(a) ........
.....................
Noy discontinuity coordinate.
The log n value of the inter-
section point of the straight
lines representing the vari-
ation of SPL with log n.
M(b), M(c),
etc.
.....................
Noy inverse slope.
The recip-
rocals of the slopes of
straight lines representing
the variation of SPL with
log n.
n ...................
noy ..............
The perceived noisiness at
any instant of time that oc-
curs in a specified fre-
quency range.
n(i,k) .............
noy ..............
The perceived noisiness at
the k-th instant of time that
occurs in the i-th one-third
octave band.
n(k) ..............
noy ..............
Maximum perceived noisi-
ness.
The maximum value
of all of the 24 values of
n(i) that occurs at the k-th
instant of time.
N(k) ..............
noy ..............
Total perceived noisiness.
The total perceived noisi-
ness at the k-th instant of
time calculated from the 24-
instantaneous values of n
(i, k).
p(b), p(c), etc
.....................
Noy slope.
The slopes of
straight lines representing
the variation of SPL with
log n.
PNL ..............
PNdB ...........
The perceived noise level at
any instant of time. (The
unit PNdB is used instead
of the unit dB).
Symbol Unit
Meaning
PNL(k) .........
PNdB ...........
The perceived noise level cal-
culated from the 24 values
of SPL (i, k), at the k-th in-
crement of time. (The unit
PNdB is used instead of
the unit dB).
PNLM ...........
PNdB ...........
Maximum perceived noise
level.
The maximum value
of PNL(k). (The unit PNdB
is used instead of the unit
dB).
PNLT ...........
TPNdB .........
Tone-corrected perceived
noise level.
The value of
PNL adjusted for the spec-
tral irregularities that occur
at any instant of time. (The
unit TPNdB is used instead
of the unit dB).
PNLT(k) .......
TPNdB .........
The tone-corrected perceived
noise level that occurs at
the k-th increment of time.
PNLT(k) is obtained by ad-
justing the value of PNL(k)
for the spectral irregularities
that occur at the k-th incre-
ment of time. (The unit
TPNdB is used instead of
the unit dB).
PNLTM ........
TPNdB .........
Maximum tone-corrected per-
ceived noise level.
The
maximum value of PNLT(k).
(The unit TPNdB is used in-
stead of the unit dB).
PNLT
r
..........
TPNdB .........
Tone-corrected perceived
noise level adjusted for ref-
erence conditions.
s (i, k) ..........
dB ................
Slope of sound pressure
level.
The change in level
between adjacent one-third
octave band sound pres-
sure levels at the i-th band
for the k-th instant of time.
D
s (i, k) ........
dB ................
Change in slope of sound
pressure level.
s
′
(i, k) .........
dB ................
Adjusted slope of sound pres-
sure level. The change in
level between adjacent ad-
justed one-third octave
band sound pressure levels
at the i-th band for the k-th
instant of time.
s¯
(i, k) ..........
dB ................
Average slope of sound pres-
sure level.
SPL ..............
dB re ...........
20
µ
Pa
Sound pressure level.
The
sound pressure level that
occurs in a specified fre-
quency range at any instant
of time.
SPL(a) .........
dB re ...........
20
µ
Pa
Noy discontinuity coordinate.
The SPL value of the inter-
section point of the straight
lines representing the vari-
ation of SPL with log n.
SPL(b) .........
SPL (c)
dB re ...........
20
µ
Pa
Noy intercept.
The intercepts
on the SPL-axis of the
straight lines representing
the variation of SPL with
log n.
SPL (i, k) .....
dB re ...........
20
µ
Pa
The sound pressure level at
the k-th instant of time that
occurs in the i-th one-third
octave band.
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