Sound calibrator
Class 1, 114 dB, 1 kHz | Type 4231 Bruel and Kjaer

Sound Calibrator Type 4231 is a handy, portable sound source for calibration of sound level meters and other sound measurement equipment. The calibrator is very robust and stable, and conforms to EN/IEC 60942 Class LS and Class 1, and ANSI S1.40-1984.
Sound Calibrator Type 4231 is a pocket-sized, battery operated sound source for quick and direct calibration of sound level meters and other sound measuring systems. It fits Brüel & Kjær 1" microphones and using the removable adaptor, 1/2" microphones. With optional adaptors, it can be used for 1/4" and 1/8" microphones as well.

The calibration frequency is 1000 Hz (the reference frequency for the standardised international weighting networks), so the same calibration value is obtained for all weighting networks (A, B, C, D and Linear). The calibration pressure of 94 ± 0.2 dB re 20 mPa is equal to 1 Pa or 1 N/m2. The + 20 dB level step gives 114 dB SPL, which is convenient for calibration in noisy environments, or for checking linearity.