Getting to Grips with Aircraft Noise

10 - MEASURING NOISE
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10. MEASURING NOISE
This section quickly describes the basics of noise measurement.
10.1. INTRODUCTION
The equipment needed to quantify noise levels is basically composed of :
• A microphone for the signal measurement
• A recorder
• A spectrum analyzer for frequency distribution determination.
Though the dB(A) is directly measurable, other quantities (such as the EPNdB) have to
be calculated. This is one of the tasks achieved by the analyzer.
10.2. MICROPHONES
The mikes typically used for the estimation of aeroplanes noise emissions are pressure
and capacitor microphones.
Indeed the physical quantity that can be directly accessed is the air pressure (as a
function of the time) through the capacity variation of a condenser.
For aircraft acoustics, the mikes will be mounted “grazing” (see picture). This
configuration allows to keep an quasi-constant incidence of the acoustic wave on the
mike during the event duration, which is a pre-requisite to determine the corresponding
EPNL (for instance during certification tests).
0°
Grazing incidence (90°)
Mike
Flight Operations Support & Line Assistance
Getting to grips with aircraft noise