Federal Aviation Administration, DOT
Symbol

Unit

Meaning

Symbol

Unit

Meaning

F (i, k) ..........

dB ................

Delta-dB. The difference between the original sound
pressure level and the final
background sound pressure
level in the i-th one-third
octave band at the k-th interval of time. In this case,
background sound pressure
level means the broadband
noise level that would be
present in the one-third octave band in the absence of
the tone.
dB-down. The value to be
subtracted from PNLTM
that defines the duration of
the noise.
Relative humidity. The ambient atmospheric relative humidity.
Frequency band index. The
numerical indicator that denotes any one of the 24
one-third octave bands with
geometrical mean frequencies from 50 to 10,000
Hz.
Time increment index. The
numerical indicator that denotes the number of equal
time increments that have
elapsed from a reference
zero.
Logarithm to the base 10.
Noy discontinuity coordinate.
The log n value of the intersection point of the straight
lines representing the variation of SPL with log n.
Noy inverse slope. The reciprocals of the slopes of
straight lines representing
the variation of SPL with
log n.
The perceived noisiness at
any instant of time that occurs in a specified frequency range.
The perceived noisiness at
the k-th instant of time that
occurs in the i-th one-third
octave band.
Maximum perceived noisiness. The maximum value
of all of the 24 values of
n(i) that occurs at the k-th
instant of time.
Total perceived noisiness.
The total perceived noisiness at the k-th instant of
time calculated from the 24instantaneous values of n
(i, k).
Noy slope. The slopes of
straight lines representing
the variation of SPL with
log n.
The perceived noise level at
any instant of time. (The
unit PNdB is used instead
of the unit dB).

PNL(k) .........

PNdB ...........

PNLM ...........

PNdB ...........

PNLT ...........

TPNdB .........

PNLT(k) .......

TPNdB .........

PNLTM ........

TPNdB .........

PNLTr ..........

TPNdB .........

s (i, k) ..........

dB ................

Ds (i, k) ........

dB ................

s- (i, k) .........

dB ................

s (i, k) ..........

dB ................

SPL ..............

dB re ...........
20 SectionPa

SPL(a) .........

dB re ...........
20 SectionPa

SPL(b) .........
SPL (c)

dB re ...........
20 SectionPa

SPL (i, k) .....

dB re ...........
20 SectionPa

The perceived noise level calculated from the 24 values
of SPL (i, k), at the k-th increment of time. (The unit
PNdB is used instead of
the unit dB).
Maximum perceived noise
level. The maximum value
of PNL(k). (The unit PNdB
is used instead of the unit
dB).
Tone-corrected perceived
noise level. The value of
PNL adjusted for the spectral irregularities that occur
at any instant of time. (The
unit TPNdB is used instead
of the unit dB).
The tone-corrected perceived
noise level that occurs at
the k-th increment of time.
PNLT(k) is obtained by adjusting the value of PNL(k)
for the spectral irregularities
that occur at the k-th increment of time. (The unit
TPNdB is used instead of
the unit dB).
Maximum tone-corrected perceived noise level. The
maximum value of PNLT(k).
(The unit TPNdB is used instead of the unit dB).
Tone-corrected perceived
noise level adjusted for reference conditions.
Slope of sound pressure
level. The change in level
between adjacent one-third
octave band sound pressure levels at the i-th band
for the k-th instant of time.
Change in slope of sound
pressure level.
Adjusted slope of sound pressure level. The change in
level between adjacent adjusted one-third octave
band sound pressure levels
at the i-th band for the k-th
instant of time.
Average slope of sound pressure level.
Sound pressure level. The
sound pressure level that
occurs in a specified frequency range at any instant
of time.
Noy discontinuity coordinate.
The SPL value of the intersection point of the straight
lines representing the variation of SPL with log n.
Noy intercept. The intercepts
on the SPL-axis of the
straight lines representing
the variation of SPL with
log n.
The sound pressure level at
the k-th instant of time that
occurs in the i-th one-third
octave band.

h ...................

dB ................

H ..................

Percent ........

i ....................

.....................

k ...................

.....................

Log ...............
log n(a) ........

.....................
.....................

M(b), M(c),
etc.

.....................

n ...................

noy ..............

n(i,k) .............

noy ..............

n(k) ..............

noy ..............

N(k) ..............

spaschal on DSK3GDR082PROD with CFR

Pt. 36, App. A

noy ..............

p(b), p(c), etc

.....................

PNL ..............

PNdB ...........

793

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