Self-Noise Characteristics of Nose-Cone Protected 1/2"-Microphones.

Kurzfassung

In order to avoid flow-induced tonal-noise as typically generated at standard B&K nose-cones, NLR developed a new type of nose-cone with different cone-shape and grid cover. Self-noise measurements were conducted in the DLR aeroacoustic behaviour of this design and to comparethe results against those from standard B&K nose-cones. NLR nose-cone self-noise characteristics turn out to be extremely sensitive towards off-axis inflow conditions, i.e. for attitude angles in excess of about 2 deg. Below this 2 deg attitude angle no tones are observed, while at higher microphone axis attitude both tones and excessive broadband noise levels occur.