Larson Davis 831C-FFT, Справочное руководство

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SoundAdvisor Model 831C Understanding Calibration Values 48
Module 5 Calibrating Your SoundAdvisor 831C
T
his module covers acoustic calibration of your SoundAdvisor 831C. This is the most
commonly used calibration method, and the one required by most national and
international standards prior to making a measurement.
In acoustic calibration, a sound level calibrator provides an acoustic signal of a known
amplitude and frequency to the microphone. From the voltage level measured by the
meter, the you can determine the sensitivity of the microphone.
In this technique, we assume that the calibrator is functioning correctly and that we’re
using the most appropriate calibrator for the instrument and intended use. Any variation
from the expected level results in improper calibration and incorrect sensitivity values.
In this module:
5.1 Understanding Calibration Values ...................................................................................... 48
5.1.1 Determining Microphone Sensitivity
5.1.2 Determining Noise Floor, Overload, and Under Range Levels
5.1.3 Understanding Calibration Stability
5.2 Choosing a Calibrator .......................................................................................................... 50
5.3 Reviewing the Calibration Settings ..................................................................................... 50
5.4 Calibrating Your SoundAdvisor 831C .................................................................................. 53
5.4.1 Calibrating While Using Meter Security (Lock Mode)
5.4.2 Performing an E.A. Check
5.1 Understanding Calibration Values
This section reviews the values tied to the calibration results and helps you interpret them.
Accurate calibration values contribute to quality sound level measurements.
In this section:
• 5.1.1 Determining Microphone Sensitivity
• 5.1.2 Determining Noise Floor, Overload, and Under Range Levels
5.1.1 Determining Microphone Sensitivity
The primary role of sound level meter calibration is to establish a numerical relationship
between the sound level at the diaphragm of the microphone and the voltage measured
by the meter so that the sound pressure level can be read directly from the display of the
meter in dB. The result of a calibration is the determination of the sensitivity of the meter,
including microphone and preamplifier, typically in dB re 1V/Pa or mV/Pa.
5.1.2 Determining Noise Floor, Overload, and Under Range Levels
A secondary role of calibration is to determine the sound level which would overload the
instrument (Input Overload level) and the minimum sound level (Under Range level) that
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