This article discusses a new project by NIST aimed at improving acoustical calibration methods using optical sensing techniques. Two main approaches are being explored: one involves using a laser Doppler vibrometer (LDV) to measure microphone volume velocity, which could simplify and improve the accuracy of secondary microphone calibrations at standard frequencies like 250 Hz and 1 kHz. This method is expected to save time and reduce costs.
The second approach uses optical measurements of refractive index changes to measure sound pressure, known as the refractive index sound standard (RISS). This method could offer a new way to trace sound pressure measurements back to a quantum standard, allowing for more accurate and versatile calibrations across a wider range of devices and frequencies. The project is still in the research and development phase, with potential long-term impacts on acoustic measurement accuracy and traceability.
Keywords: optical sensing, refractive index sound standard, laser Doppler vibrometer
