Netherlands Ministry of
Defence
Directorate of Projects &
Procurement
Projects Procurement Division

Date

22 January 2009

Our reference

ANNEX

Aircraft Noise Measurements
When comparing the noise impact of two different types of aircraft, it is important to measure
the noise and aircraft flight performance data with a similar accuracy and method.
This requires a comparable data set with respect to the flown profiles and corresponding
power settings, speeds, altitudes etc. Furthermore a comparable noise measurement set-up,
a comparable analysis and calculation of the noise are required. With the provided levels we
also need a description of the acoustical ground properties and information on the
meteorological conditions (wind speed, direction, temperature, humidity and atmospheric
pressure [refresh rate of 1 Hz] during the measurements (at the ground and at 300 ft altitude
at the location of the measurements) at the noise measurement site where the microphones
are placed.
The take off, landing and cruise profiles and weight for a Gripen NG with external stores (2
fuel tanks including fuel, launchers, weapon pylons, targeting pod and jammer) must be
available. This configuration must be used for the measurement of noise.
For the take-off and landing profiles the following information is required: position, altitude,
time, speed and power setting for take-off, flyover and approach.
The noise recordings are required:
o below the aircraft, measured with a microphone on a hard ground plate and a
microphone at a 4 ft pole,
o at both sides of the flight path: at distances of 125ft, 250ft, 500 ft, 1000ft, 2000ft and
4000ft from the centreline with a microphone at a 4ft pole,
o at 1000ft from the centreline at both sides with a microphone at 125 ft and 250 ft
AGL.
The noise data format is raw data (sample rate min 100kHz, 24 bits) from recordings of noise.
The aircraft performance data must have a refresh rate of 10Hz.
In the Netherlands the LAmax is being used for calculating the noise contours in the vicinity of
airbases. The LAmax is the A-weighted maximum sound level. This maximum sound level is
determined by integrating the Sound Pressure Level with a period of 1 second. In type I
sound level meters this is known as the option "slow". From the raw data the LAmax levels
will be derived by NLR. With the flight performance data/flight profiles data and the LAmax
data, NLR can calculate the noise contours.

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Netherlands Ministry of
Defence
Directorate of Projects &
Procurement
Projects Procurement Division

Date

22 January 2009

Our reference

The following procedures are an example for a data set:
1. Horizontal fly-over at 1000 ft with a constant speed of 230 knots
2. Horizontal fly-over at 1000 ft with a constant speed of 275 knots
3. Horizontal fly-over at 1000 ft with a constant speed of 330 knots
4. Horizontal fly-over at 1000 ft in full AB, with a speed of 275 knots
5. Horizontal fly-over at 1000 ft in mil power, with a speed of 275 knots
6. Horizontal fly-over at 1000 ft in 90% mil power, with a speed of 275 knots
7. Horizontal fly-over at 1000 ft in 75% mil power, with a speed of 275 knots
8. Horizontal fly-over at 1000 ft in 50% mil power, with a speed of 275 knots
9. Horizontal fly-over at 1000 ft in cruise, wheels up
10. Horizonal fly-over at 1000 ft in cruise, wheels down
11. Horizontal fly-over at 1000 ft in approach configuration
12. Simulated Take-off at 1000 ft in MIL power
13. Simulated Take-off at 1000 ft in AB.
This data set must be representative for the speed, altitude and power settings during the
take-off, landing and cruise near a military airbase.

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