measurement microphone / prepolarized / condenser / 1/4"
Bruel and Kjaer
The 4939 is a ¼-inch free-field microphone (4 Hz to 100 kHz, 200V polarization) which is a top of the line product designed by Bruel and Kjaer. It features a sensitivity of 4 mV/Pa and a frequency of 4 100,000 Hz. It's dynamic range is 28 164 dB, but it features a temperature of 40 to 150°C(40 to 302°F) along with a polarization of 200 V External.
It is mostly used for high level measurements and frequency measurements as well as model work. It is composed of stainless steel diaphragm and protection grid. It is designed to withstand harsh environments.