GRAS releases a microphone with measurement capabilities at extremely low acoustic frequencies for performing aerospace noise tests.
Following collaboration with aerospace industry partners, including the Japanese Space Exploration Agency or JAXA, GRAS Sound & Vibration has developed the 47AC Microphone Set which sets a new benchmark for infrasound measurements.
Increased awareness about infrasound and the discomfort that noise and low frequencies can generate has resulted in new measurement challenges from the aerospace industry for accurate and reliable monitoring of environmental noise. The main requirement is to measure at extremely low frequencies.
As pioneers in infrasound measurements, GRAS has been working with a number of industry partners to develop its new 47AC Microphone Set.
The GRAS 47AC 1/2” Infrasound Microphone Set is a CCP (Constant Current Power) free-field instrument, designed specifically for the demands of infrasound testing, allowing the measurement of frequencies as low as 0.09Hz. The 47AC is the only infrasound microphone on the market with this capability.
Helping JAXA – The Japanese Space Exploration Agency
Prior to the launch of the 47AC, GRAS has worked extensively with JAXA to develop testing equipment that enables realistic measurements of sonic booms generated by sonic aeroplanes.
As low flying sonic aeroplanes over land becoming increasingly viable, reducing the impact of the sonic boom generated by supersonic aircraft is vital.
Central to this is the accurate measurement of the effects of the sonic boom. Flight testing is extremely costly and to capture sonic boom pressure time histories in detail, infrasound test equipment has to be accurate, flexible and reliable – every time.
GRAS is now offering the 47AC 1/2” CCP Infrasound Microphone Set as a standard product amongst its extensive portfolio. This is directly as a result of working with JAXA to find a customised product for the ‘Drop test for Simplified Evaluation of Non-symmetrically Distributed Sonic Boom’ (D-SEND) project.
According to GRAS Director and Owner Per Rasmussen, the partnership with JAXA has resulted in a thorough knowledge about the measurement challenges within infrasound. “Building upon these experiences we have now developed a standard product with the unique feature to measure at extremely low frequencies – as low as 0.09Hz.”
The 47AC can be used for infrasound monitoring applications within different industries including measurement of wind turbine noise and university research.
The 47AC is the only infrasound microphone with a CCP and the set is assembled and calibrated as a complete unit. It offers a frequency range from 0.09Hz to 20kHz, dynamic range from 20dB(A) to 148dB and sensitivity 8Mv/Pa.