- - 1/2" Prepolarized Free-Field Microphones- Class 1
- - 1/2" Prepolarized Free-Field Microphones- Class 2
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There are three types of sound field measurement microphones for use in different testing environments: free-field microphone, pressure-field microphone, and random-incidence microphone. When mak ing a measurement at frequencies below 5000Hz , the differences of the measurements using the above three types of microphones are within 0.3 dB. The measurement difference could be higher than 10 dB at the high frequencies above 16kHz. Therefore, choosing the right microphone is a must for making accurate measurements. - Random- incidence Microphone: USA standard has requests for random-incidence microphones. So to make the measurement conform to the USA ANSI standard, a random incidence microphone may be required. - Free-field Microphone: A microphone can change the sound field in which it is placed. A free-field microphone is designed to compensate for the influence of its presence in the sound field. So it can measure the sound pressure as it existed before the microphone was introduced into the sound field and can be used in such environments as outdoors, anechoic room, or reverberation room. - Pressure-field Microphone: a pressurefield microphone can measure the sound pres sure ex i s t ing on the diaphragm of the microphone. It can be used in a coupler environment such as an ear simulator or to test the sound pressure on a surface. |
MP251 and MP253 are 1/2’ ’pressure-field microphones and are designed to make the measurement in an ear simulator, a coupler or the sound pressure on a surface. MP451 is 1/4" pressure-field microphone. |
SPECIFICATIONS
| PRESSURE-FIELD MICROPHONES MP251/MP253/MP451 | |||
|---|---|---|---|
| Model | MP251 | MP253 | MP451 |
| Diameter | 1/2 inch | 1/2 inch | 1/4 inch |
| Open-Circuit Sensitivity | -40 dB±3 dB (10 mV/Pa) | -26 dB±3 dB (50 mV/Pa) | -48 ±3 dB (4 mV/Pa) |
| Capacitance (Typical) | 16 pF | 16 pF | 16 pF |
| Response | Pressure Field | Pressure Field | Pressure Field |
| Polarization Voltage | 0 V | 0 V | 0 V |
| Frequency Response | 8 Hz ~ 20 kHz | 8 Hz ~ 10 kHz | 20 Hz ~ 70 kHz |
| Dynamic Range (3% Distortion Limit) | > 146 dB | > 146 dB | > 170 dB |
| Cartridge Thermal Noise | < 20 dB (A) | MP253 | < 40 dBA |
| Pressure Equalization Vent | Rear Vented | Rear Vented | Rear Vented |
| Operating Temperature | -30°C ~ 80°C | -30°C ~ 80°C | -20°C ~ 80°C |
| Operating Humidity | 0 ~ 98% RH | 0 ~ 98% RH | 0 ~ 98% RH |
| Equivalent Air Volume | 250 mm3 at 250 Hz | 250 mm3 at 250 Hz | |
| Temperature Coefficient (-10°C ~ 50°C) | - 0.008 dB/°C | - 0.008 dB/°C | - 0.008 dB/°C |
| Humidity Coefficient | -0.006 dB/%RH | -0.006 dB/%RH | -0.006 dB/%RH |
| Pressure Coefficient (250 Hz) | -0.005 dB/kPa | -0.005 dB/kPa | -0.005 dB/kPa |
| Dimensions | Length: 13 mm IEC 61094-4 Type WS 2P |
Length: 16.7 mm IEC 61094-4 Type WS 2P |
Length: 10.5 mm IEC61094-4 WS3F |
