Towards aeroacoustic measurements under hyperbaric condition

Abstract

Full scale experimental aeroacoustic measurements are often impractical due to the prohibitively high costs associated with full scale models and large facilities capable of far-field acoustic measurements. Although small scale models can provide useful acoustic data, this scaling is limited by the inability to achieve full scale equivalent aerodynamic conditions at smaller scale. However, aerodynamic similarity can theoretically be achieved using much smaller models under hyperbaric conditions. While promising, microphones and anechoic materials used in acoustic experimentation are not explicitly designed for use in such conditions, and so their behavior must be verified. To characterize the response of condenser microphones at elevated pressures, a pistonphone style calibrator was developed to operate over a range of pressures. Likewise, for the anechoic materials, an impedance tube was developed to evaluate their performance at elevated pressures. The performance of these systems under atmospheric pressure and hyperbaric conditions is discussed, along with details of the experimental method, and observed microphone response, and acoustic insulation performance at high pressure.