8-14 Sensitivity Tab Model 831 Manual
FIGURE 8-12 Sensitivity Tab
Noise Floor
The noise floor is calculated as the energy sum of the
microphone self noise, preamplifier self noise and
instrument self noise.
The appropriate noise floor, as well as the nominal
sensitivity, is computed automatically in the Model 831 with
the following preamplifiers and their commonly paired
microphones:
• PRM 831
• PRM2103
• 426A12
• ICP with ADP074
When a calibration has been performed using any of the
preamplifiers listed above, that calibration information is
saved for that preamplifier. If the preamplifier is switched
from one of these types to another, then the calibration
information already saved for that new preamplifier type is
recalled. As long as the same microphone is being used with
that preamplifier, the calibration should be correct.
Direct Data Input
Self-noise values can also be entered manually when using
preamplifiers and/or microphones not included in the Model
831 data base.
Overload Level
The overload level is the highest peak level which can be
measured without overloading the input of the Model 831.
Under Range Level
The Under Range Level is the higher of the following:
(1) Noise Floor plus 9.14 dB (under range shown when self
noise contributes
0.5 dB to the readings).
(2) Actual point where the log-linearity exceeds maximum
permitted value
Except for very low noise level microphones, the under
range level is usually determined by (1).
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