TYPE 4178

• Broadband matching of phase responses
• Phase calibrated in 1/3-octave frequency bands from 100 Hz – 20 kHz

Type 4939 microphones are specially designed for high-level and high-frequency measurements. By using stainless steel diaphragm and protection grid, the microphone is optimized to withstand rough environments and is capable of working at high temperatures – up to 150°C (302°F). The microphones are mainly used in Sound Intensity Probes for sound power and intensity measurements, and can also be used for particle velocity measurements.

Type 4178 is supplied with 6 mm and 12 mm spacers, along with calibration charts giving the individually measured free-field frequency response for each microphone and a Phase Response Comparison Calibration (100 Hz – 20 kHz).

Phase calibration of 1/4-inch microphone pair Type 4178 is done at Brüel & Kjær by subjecting the two microphones to the same sound signal in a pressure coupler. This individual phase calibration can be used to derive the Pressure-Residual Intensity Index for the microphone pair.

Sound intensity measurement systems containing a sound intensity probe set can be conveniently calibrated using
Sound Intensity Calibrator Type 3541-A. This permits simultaneous sensitivity adjustment of both channels of the processor (in pressure, particle velocity, or intensity modes) and allows determination of the 20 Hz – 5 kHz Pressure-Residual Intensity Index of the probe and processor combinations.