1/2" prepolarized condenser pressure microphone
50 mV/Pa | EM40AD Meggitt Sensing Systems - Measurement Group

The Endevco microphone model EM40AD is a ½-inch precision condenser microphone for general purpose acoustic measurements, e.g. in couplers, boundaries and in enclosures; it can also be used as a random-incidence microphone. It is a prepolarized pressure microphone with a large dynamic range and a wide frequency response.

As a pressure microphone, the model EM40AD measures the sound pressure at the location of its diaphragm. It has a flat pressure-frequency response over its entire working frequency range (see Fig.1).

In an open sound field, a pressure microphone will also include the disturbing effects of its presence in the sound field. These are minimal at low frequencies (large wavelengths compared with microphone size).

At higher frequencies the effects of reflections and diffractions must be accounted for. Generally, they lead to an increase in the measured sound pressure and corrections have to be made. Fig.2 shows what these corrections are in a free field for various angles of incidence.

Endevco Isotron® preamplifiers are also available for use with the model EM40AD, these are:
½-inch preamplifier model EM26CA
¼-inch preamplifier model EM26CB with adaptor