Measurement microphones are accurate and reliable devices designed to be used for quantify acoustics signals. Still, even with the sturdiest build and the best handling and care, microphones do suffer from wear and tear.
It is recommended to perform regular calibrations for measurement microphones to maintain level accuracy, sensitivity and frequency response checks. If a microphone is used extensively or operated in humid and warm environments, annual calibration is recommended to ensure the microphone works its best with as little room for error as possible.
250 Hz Pistonphone
There are 2 ways of calibrating a measurement microphone, level and sound calibration. For level calibration, a pistonphone is used for as a precise sound source for the calibration. As a pistonphone relies on air pressure, the ambient pressure, humility and air in the environment has to be analysed and monitored before and during calibration. With this, pistonphone are generally only made to reproduce low frequencies typically 250 Hz.
Sound calibrators are another sound source used in calibration and they are not affected by ambient pressure and cavity volume. Sound calibrators work electronically and are considered as an electrodynamic source for calibration, usually generating a 1000 Hz tone to the microphone. Due to sound calibrators relying on an electrodynamic sound source, there is a slight increase in chances of error making them less precise than mechanical-based pistonphones.
With this, it is recommended that both types of calibration are done during microphone calibration to ensure the precision of the instrument. A level calibration that relies on a mechanical piston followed by a sound calibration that uses an electrodynamic sound source. Both calibrations have their possible margin of errors (even though negligible) which leads to a need for ambient pressure testing before level calibration and sound calibrators needing to be calibrated by the certifying bodies. Together, both types of calibration ensure microphones work properly and with precision.
TME Systems is a Measurement Microphone Calibration Centre in Singapore and South East Asia that uses both pistonphones and sound calibrators for calibration. To arrange for an appointment to calibrate your measurement microphone with us or to learn more, contact TME Systems today!