Pressure calibration of ws3 microphones

Applications of sound measurements at frequencies above the audible frequency range, such as studies of involuntary exposure ultrasound, measurement of exposure to ultrasound in industrial spaces, failure detection in aeronautic structures, and the investigation of the perception mechanisms of ultrasound may require that the sensitivity of the microphone is known at frequencies up to 100 kHz. In any of these applications, it is critical to establish a well defined traceability chain to SI units to support any measurement result. Measurements at these high frequencies are carried out using measurement microphones of small size, known as quarter-inch or working standard microphones type 3. While nowadays practically other measurement microphones such as oneinch and half-inch (working standards type 1 and 2, WS1 and WS2 respectively) can be calibrated using pressure or quasi-pressure field methods which are based on the assumption of a uniform sound pressure acting only on the membrane of the microphone. These methods include, pressure reciprocity, comparison, and the measurement of the frequency response using an electrostatic actuator. For WS3 microphones fully traceable pressure calibrations are only available up to 20 kHz30 kHz. No other method than actuator is applied at higher frequencies. In this project, attempts for calibrating WS3 microphones at frequencies up to 100 kHz have been carried out using pressure reciprocity. Results are compared to electrostatic actuator.