The Endevco microphone model EM40AM is a ½” widefrequency, precision condenser microphone for laboratory work as well as for measurements in open acoustic fields. It is a pre-polarized free-field microphone with a large dynamic range and an extended frequency response. As a free-field microphone, the model EM40AM is for measuring the sound pressure which existed before it was placed in the sound field, and pointing towards the sound source. The disturbing effects of its presence in the sound field are minimal at low frequencies (large wavelengths compared with microphone size). At higher frequencies, the effects of reflections and diffractions generally lead to an increase in the measured sound pressure levels. Fig.2 shows what these are in a free-field for various angles of incidence. The model EM40AM compensates for this to provide a flat frequency response at an angle of 0° incidence in a freefield (see Fig.1). Endevco Isotron® preamplifiers are also available for use with the model EM40AM, these are: • ½” preamplifier model EM26CA • ¼” preamplifier model EM26CB with the included adaptor. 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 • Type 0 and 1 SPL measurements • Free-field measurements • Precision laboratory measurements • Use with Endevco Isotron® preamplifiers • Repairable Endevco® model EM40AM ½” Wide-frequency free-field microphone Description cmyk

Endevco® model EM40AM ½” Wide-frequency free-field microphone Specifications Frequency response: 3.15 Hz–31.5 kHz ± 2.0 dB 5 Hz–16 kHz ± 1.0 dB 3.15 Hz–40 kHz ± 3.0 dB Nominal sensitivity: 12.5 mV/Pa Polarization voltage: 0 V Dynamic range: Upper limit (3% distortion) 160 dB re. 20 ìPa Microphone thermal noise: 20 dBA re. 20 ìPa Capacitance: 17 pF Temperature range: –10°C to +50°C (14°F to 122°F) Temperature coefficient (250 Hz): -0.008 dB/°C Static-pressure coefficient: -0.008 dB/kPa Humidity range: 0–100% (non-condensing) Influence of humidity (250 Hz): < 0.1 dB (0–100% RH) Influence of axial...