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Endevco® model EM40AQ ½” prepolarized random-incidence microphone

Endevco® model EM40AQ ½” prepolarized random-incidence microphone
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Endevco® model EM40AQ ½” prepolarized random-incidence microphone - 1

The Endevco microphone model EM40AQ is a ½-inch precision condenser microphone for general purpose acoustic measurements, e.g. in diffuse fields and inside vehicles. It is a prepolarized, random-incidence microphone with a large dynamic range and a wide frequency response. As a random-incidence microphone, the model EM40AQ measures the sound pressure which existed before it was placed in a diffuse sound field. It will, however, also include the disturbing effects of its presence in a 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 and, based on these, random incidence. The random-incidence correction curve in Fig.2 is defined as described in ANSI standard S1.10. Fig.1 shows a frequency response typical of a model EM40AQ when placed in a diffuse sound field. Endevco Isotron® preamplifiers are also available for use with the model EM40AQ, these are: • ½-inch preamplifier model EM26CA • ¼-inch preamplifier model EM26CB with adaptor All Endevco microphones comply with the specifications of IEC 1094: Measurement Microphones, Part 4: Specifications for working standard microphones. Non-corrosive, stainless materials are used in manufacturing these microphones to enable them to withstand rough handling and corrosive environments. All Endevco microphones are guaranteed for 5 years and are individually checked and calibrated before leaving the factory. An individual calibration chart is supplied with each microphone. Applications • Precision acoustic measurements • Diffuse-field measurements • Inside-vehicle measurements • Use with Endevco Isotron® preamplifiers • Repairable Endevco® model EM40AQ ½” Prepolarized random-incidence microphone Description cmyk

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Endevco® model EM40AQ ½” prepolarized random-incidence microphone - 2

Endevco® model EM40AQ ½” Prepolarized random-incidence microphone Specifications Frequency response: 3.15 Hz–12.5 kHz: ± 2.0 dB 12.5 Hz–8 kHz: ± 1.0 dB Resonant frequency: 90 ° phase shift: 14 kHz Nominal sensitivity: at 250 Hz: 50 mV/Pa Polarization voltage: 0 V Dynamic range: Upper limit (3% distortion): 148 dB re. 20 ìPa Microphone thermal noise: 16 dB re. 20 ìPa Capacitance: Polarized: 13.3 pF Effective front volume: Nominal at 250 Hz: 50 mm3 Temperature range: –40°C to +120°C (-40°F to 248°F) Temperature coefficient (250 Hz): –10°C to +50°C: –0.01 dB / °C Static-pressure coefficient:...

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