Larson Davis 831C-FFT, Справочное руководство

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SoundAdvisor Model 831C C-13
Projected Noise Dose
Projected Noise Dose is the
Noise Dose
expected if the current rate of noise exposure continues
for the full
Criterion Duration
period.
Quality Indicators
A portion of Tonality standard (ISO 1996-2, or ISO/PAS 20065), which rates the audibility of tones
in a measured spectrum according to the following values:
Lpt
: the sound pressure level of tones in the critical band.
Lpn
: Sound pressure level of the masking noise in the critical band.
DeltaLta
: Tonal Audibility, or the difference between the SPL of the tones and the SPL of the
masking noise. (Lpt–Lpn)
Kt
: Possible adjustment to the measured sound pressure level that may be suggested to account
for the impact of more prominent tones on the human ear.
Regression Range
When applying the 1996-2 Tonality standard, the Regression Range value enables you to set what
percentage of the critical band should be represented to the left and right of the center frequency.
For example, selecting 75% results in a range that is 75% to the left and 75% the right of
the center frequency. A higher percentage displays more regression noise data.
The
Regression Range setting is located on the
Setup Manager

Tonality tab
. For details, see
18.3
"Making the FFT Measurement" on page 145 .
For details on defining a regression range, see ISO 1966-2 C.4.4.
Single Event Noise Exposure Level (SENEL, LAX)
The Single Event Noise Exposure Level is the total sound energy over a specific period. It is a spe-
cial form of the
Sound Exposure Level
where the time period is defined as the start and end
times of a noise event such as the passing of an aircraft or automobile.
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 annoy-
ance. 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)
Sound Exposure is the total sound energy of the actual sound during a specific time period. It is
expressed in Pascals-squared seconds, or Pascals-squared hours. The following formula describes