Noise measurements in wind tunnel tests are difficult due to the excessive levels of noise created by the wind tunnel flow. At low speeds specialized open jet anechoic wind tunnels are used to minimize the tunnel noise. While this is the preferred solution it is not always possible to set up a special test just for acoustics and measurements must be conducted in standard wind tunnels simultaneously with other data collection. When this is necessary we use specialized signal and array processing techniques to reject the tunnel induced noise and retain only the acoustic signature created by the test model.

A generic model of the weapons bay of a transonic fighter aircraft is tested in a transonic wind tunnel (CHANNEL 5). A 6 element array of microphones mounted in the tunnel sidewall measures the radiated noise.

Full spectrum

After rejecting
tunnel noise