B&K 4230 Sound Level Calibrator

Unit in protective leather case.

The Bruel & Kjaer 4230 Sound Level Calibrator is designed for the calibration of 1'' and 1/2'' diameter microphones. An adaptor is placed over the opening for use with 1/2'' microphones and is removed when 1'' microphones are to be calibrated. The calibrator should be stored and operated in its leather case. The sound pressure level produced by the 4230 is 94 dB re 20 µPa. However, when calibrating a microphone which is to be used for free field measurements, a small correction is necessary to compensate for the difference between free field response at 0° incidence and the pressure response. The correction is -0,4 dB for 1'' free field microphones and -0,2 dB for 1/2" free field microphones. This makes the effective calibration levels 93,6 dB and 93,8 dB respectively. No correction is required when calibrating pressure response microphones.