Rattle near Gilze-Rijen en Hulten

Commissioned by the Dutch ministry of defense, NLR and TNO have conducted research into the role of overflying helicopter sounds. When a Chinook helicopter flies over, people may be exposed to a certain noise level that could cause annoyance. In addition, secondary sound (“rattle”) may occur indoors as a result of the dwelling being excited by low-frequency sound (<100 Hz), which can cause objects to vibrate.

The ministry of defense has compiled an inventory of the dwellings around the airbase where rattle may occur as a result of helicopters flying over. Based on research, 275 dwellings were selected. These are dwellings where the noise from air traffic exceeds the threshold used by the Ministry of Defense.

Of these 275 dwellings, 15 dwellings were investigated and processed in more detail as pilot dwellings in a preliminary phase. In this preliminary phase, Witteveen+Bos (W+B) determined the required measures to reduce the rattle noise in collaboration with Level Acoustics & Vibration. This resulted in 15 packages of measures tailored to the specific pilot dwellings and a general assessment framework that can be applied to determine the measures for the remaining 260 dwellings.

Measurements were carried out both before and after execution of the measures to assess the rattle noise occurring in the dwellings and measure the low-frequency sound insulation. During the measurements, the sound source – a truck containing 6 subwoofers (see photo above) – was positioned approximately at a distance of 10 meters from the façade of the dwellings to be exposed to low-frequency sound. The area around the dwellings was closed off to prevent people without hearing protection from getting too close. The measurement results determined to what extent these measures improve low-frequency sound insulation and reduce the occurrence of rattle noise.

Watch a fragment of the measurements here:

https://www.bndestem.nl/video/productie/eerste-tests-tegen-rattle-noise-in-hulten-en-gilze-2003688