The Acoustic Response of Measurement Microphones under Hyperbaric Conditions

Reducing noise is crucial for rotorcraft and wind turbines. Collecting accurate acoustic measurements requires large-scale field studies, but conducting field experiments can be difficult due to space constraints and high costs. Testing small-scale models in a pressurized environment can resolve this challenge because the conditions are dynamically similar to the full-scale. However, measuring acoustic emissions in a compressed air environment introduces new challenges, including determining any changes in microphone performance as the background static pressure increases. This study explores the sensitivity of a condenser microphone to changes in pressure. Experiments are underway to calibrate a microphone using a custom-designed single-piston pistonphone and a pressure vessel. This work enables compressed air wind tunnels or other compressed air facilities to incorporate acoustic measurements into their model testing.