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New, precise and cost-optimized measuring microphone M 380 based on microelectromechanical systems (MEMS)

MEMS microphones have been widely used in the consumer sector in recent years.

The main reasons for their increasing popularity are their reliable monolithic structure, low height and high resistance to mechanical vibrations and temperatures.

Basically, they are constructed like condenser microphones, but manufactured on a printed circuit board using silicon technology, with dimensions in the millimeter range and comparatively low production costs.

An integrated circuit (ASIC / Application Specific Integrated Circuit) provides the polarization voltage for a flexibly suspended diaphragm that moves freely over a fixed backplate and the signal amplification.

This structure forms a variable capacitor with a fixed electrical charge that is applied between the membrane and the backplate.

Depending on the design, the output signal can be analog or digital (with integrated A/D converter).

Due to the fact that the digital version has no influence on the type of digitization, the analogue version is more suitable for metrology applications.

But are MEMS microphones also up to the high demands of measurement technology?

The answer to this question is the newly developed M 380 from the MTG development team.

The 1/4" M 380 electret measuring microphone has a free-field equalized frequency response of the transmission ratio and is designed in particular for acoustic measurements in the free sound field with a 0 degree angle of incidence.

The electrical connection is made via Microdot or BNC cable to measurement channels with IEPE supply. The frequency response of the measuring microphone corresponds to class 1 according to IEC 61672.

Thanks to its MEMS capsule technology, the M 380 has a very low serial tolerance of sensitivity and frequency response. It is designed for acoustic measurements where multi-channel microphone arrangements are used or where easy interchangeability of microphones is an advantage.

The miniaturized, inseparable combination of microphone capsule and preamplifier can be connected to measurement channels with IEPE supply and calibrated with standard 1/4" sound calibrators.

The M 380 opens up a wide range of customized, cost-effective applications. This ranges from the use of a number of microphones in acoustic microphone arrays for enveloping surface measurement methods, e.g. by means of sound power hemispheres/SLH on measurement objects placed under a dome or in acoustic cameras, to individual microphones for customer-specific measurement tasks.