Larson Davis System 824, Техническое справочное руководство

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9/29/09 D -17
Noise Exposure
(See Sound Exposure)
OSHA Level (L
OSHA
)
The Average Sound Level calculated in accordance with the
Occupational Safety and Health Administration Exchange
Rate and Threshold Level.
Preamplifier
A part of the sound level meter that matches a particular
model of microphone to the meter. It must be chosen in
conjunction with a microphone and a cable that connects
them.
Projected Noise Dose
It is the Noise Dose expected if the current rate of noise
exposure continues for the full Criterion Duration period.
Single Event Noise Exposure
Level (SENEL, L
AX
)
The total sound energy over a specific period. It is a special
form of the Sound Exposure Level where the time period is
defined as the start and end times of a noise event such as an
aircraft or automobile passby.
Sound
The rapid oscillatory compressional changes in a medium
(solid, liquid or gas) that propagate to distant points. It is
characterized by changes in density, pressure, motion, and
temperature as well as other physical quantities. Not all
rapid changes in the medium are sound (wind noise) since
they do not propagate.
The auditory sensation evoked by the oscillatory changes.
Difference between sound and noise: Sound is the physical
phenomenon associated with acoustic (small) pressure
waves. Use of the word
sound provides a neutral description
of some acoustic event. Generally, noise is defined as
unwanted sound. It can also be defined as sound that causes
adverse effects on people such as hearing loss or annoyance.
It can also be defined as the sound made by other people. In
every case, noise involves the judgment of someone and
puts noise in the realm of psychology not physics.
Rules :
1. Use word sound to describe measurements to remove the
emotional overtones associated with the word noise . Some
sound metrics use noise in their name and it is proper to use
the name as it is.