Care and Handling of Measurement Microphones

Measurement microphones are precision instruments designed to measure sound pressure in air. Precision condenser microphones consist of a thin metal membrane in close proximity to a solid metal plate. This forms a variable capacitor that converts the motion of the diaphragm to voltage. When the microphone is exposed to a change in pressure, the resulting motion of the diaphragm causes a change in the capacitance of the microphone. The diaphragm displacement is directly proportional to the exposed sound pressure. Precision condenser microphones are the best designs for accurate acoustic testing. They are very stable over time and temperature or humidity fluctuations. The cartridges are standardized to fit onto a wide range of preamplifiers and handheld calibrators. They are the most widely used microphone type for precision sound level meters.

The diaphragm built into a microphone is extremely thin and delicate (approximately 1/8 the thickness of a standard sheet of household aluminum foil), but the device can have a long useful life with proper handling. With years of experience manufacturing and calibrating microphones, The Modal Shop and PCB have found the following handling tips useful for keeping microphones in good working order for many years

• The grid cap of a microphone should only be removed when absolutely necessary (for example, when inserting a nose cone, for electrostatic actuator calibration, or when using with certain couplers)
• Never touch the microphone diaphragm
• If precautionary measures are taken to keep the microphone clean, any minor dry dust on the diaphragm should not affect performance. If a microphone needs to be cleaned, the best option is to return it to the manufacturer for service. A light air blow bulb blown across (not directly at) the grid cap is the only type of “cleaning” that should be attempted by the end user. Never use compressed air on a microphone, and never blow air directly into the top of the grid cap.
• When attaching a microphone to a preamplifier, simply hand-tighten the microphone, taking care not to overtighten. Always assemble the microphone and preamplifier while seated at a table.
• Handle the microphone with care at all times. Microphones are susceptible to shock. Dropping a microphone may cause a shift in performance.
• The rubber caps supplied keep dirt or contamination out of the preamplifier connector. It is not intended to be used with the microphone. If this cap is for some reason placed over the microphone grid cap, a vacuum can be created upon removal, stretching the diaphragm and causing a change in sensitivity.
• Be sure to store and use the microphone at temperatures within its specified operating range. When using microphones in extreme or outdoor conditions, use appropriate protection (for example, windscreens and desiccants) to reduce the effects of wind, rain, and condensation.
• Store a microphone either attached to a preamplifier or in its original case

The following video from PCB Piezotronics demonstrates these tips