Larson Davis 824 User Manual

9-4 824 Reference Manual 9/29/09
Entering the Noise Floor Values
When measuring low levels of sound, substantial errors can
occur when the sound level to be measured is near that of the
noise floor of the measuring instrument. An accurate
measurement is obtained when the measured sound level is
at least 10 dB above the noise floor. When this condition is
not fulfilled, we say the instrument is in an Under Range
condition. which we indicate on the display. The noise due
to the front end electronics and the microphone preamplifier
are known, but the thermal noise of the microphone must be
entered by the user based on specifications provided by the
manufacturer. The A-weighted noise floor values for Larson
Davis microphones are presented in the following table.
The procedure for entering the noise floor value for the
microphone to be used is described in the section ”TTools
Key” on page 3-18, subsection ”Calibration” on page 3-22
under the heading Noise Floor.
Microphone Model Number 2520 2530 2540 377B41 2559 377A
60
2570 2575
Nominal Thermal Noise, dB(A) 30 31 20 15 18 15 10 10

Larson Davis 824 Specifications

General

Brand	Larson Davis
Model	824
Category	Measuring Instruments
Language	English