As part of its growth strategy, GRAS Sound & Vibration UK Ltd (www.gras.co.uk) – leading specialist in high performance measurement microphones and related acoustic equipment – is increasing focus on noise testing within the aerospace and defence industries. Reduction of noise emissions is critical, with manufacturers demanding increasingly sophisticated measurement instruments to ensure the continued development of quieter aircraft.
All applications bring their own challenges but aerospace testing can be one of the harshest, pushing microphones to their limits. Measurements often need to be conducted in high speed, turbulent air-flows, where it is vital that the microphone itself does not affect the results, and where the testing equipment has to be durable under extreme conditions. Often there is only one opportunity to record data so validation is vital.
GRAS UK has become an integral supplier to the aerospace and defence industries, dedicated to finding new ways of testing. From standard microphones, customised flyover arrays or microphones for extreme sounds pressures, the company’s solutions help manufacturers develop the technically advanced aircraft of the future.
The company’s high precision measurement surface microphones were originally designed for in-situ boundary layer testing where non-invasive mounting is a must. The height has remained at 2.5mm and the microphone is surrounded by a fairing to reduce self-generated turbulence. They have integrated preamplifier with plug & play functionality, and wide linear frequency and wide dynamic ranges.
GRAS UK’s flush-mount sensors combine the high precision and reliability of measurement microphones with the need for very low installation height to fit the sensors into very confined spaces and narrow structures, for example, in acoustic antennas and beams.
With an installation height of less than 10mm and thin coax wiring, the flush mount series can be integrated into literally any design without sacrificing aero-dynamic properties. They have integrated preamplifier with plug and measure functionality, wide linear frequency range and wide dynamic range.
With noise development having a considerable effect on an aircraft’s comfort and economy, GRAS UK’s simple, robust and reliable flush-mount turbulence screen microphone kit has been specially developed for accurate testing in solid walled wind tunnels in the near and far field, at low and high wind speeds.
GRAS UK’s turbulence screen is the latest innovation for aeroacoustic testing. By attenuating the hydrodynamic component of turbulence up to as much as 25 dB, the acoustic signals of interest can now be identified and diagnosed with a much more reliable resolution.
The turbulence screen integrates flush and recessed mounting techniques with a special wire mesh into one single unit and allows for adaptation of several mounting options. Key features and benefits include very high induced flow noise reduction, extremely low acoustic attenuation, low installation height, front or rear mounting options and flush-mount and standard microphone accommodation.
The kit comprises a state-of-the-art 47BX / ¼” flush mount microphone set which combines high precision and reliable noise measurement with the need for fitting sensors into very confined spaces and narrow structures. With an installation height of less than 10mm, thin coax wiring and front venting, this flush-mount microphone can be integrated into literally any design and application.
A complete all-in-one solution, the flush-mount turbulence screen kit also includes mounting flanges and a USB stick with calibration data, angle and wind speed dependency data and CAD drawings of mountable parts. It features a standard CCP connection so will be compatible with existing equipment.
In addition, the kit offers a turbulence frequency range between 500Hz – 10KhZ; acoustic attenuation less than 3db; acoustic frequency range between 100Hz – 70kHz; dynamic range between 44dBA – 166dB; approach ±60Degrees and front venting.
GRAS performs stringent testing on its measurement microphones to ensure high reliability. Using a series of highly accelerated life tests (HALT), the company ensures that its microphones live up to the high quality and precision required by aerospace and defence. GRAS HALT tests actively accelerate the lifetime of a microphone by stimulating the handling and operation in real-life situations, to ensure consistently optimal measurements.