Bruel and Kjaer 4220 Overview

Pistonphone 124dB (±0.2dB), 20µPA Sound Level at 250Hz. Calibration Accuarcy ±0.15dB.

Designed for accurate everyday calibration of sound level meters using .5 in. and 1 inch microphones. Pocket sized sound source designed for for accurate, everyday field calibration of sound level meters using .5 in. and 1 inch microphones.

• Sound pressure level 124dB
• Calibration accuracy ± 0.2dB
• Frequency 250Hz ± 1%
• Distortion < 3% at 250 Hz
• Power Source: Internal. 9 Volt battery

The 4220 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 sound pressure level produced by the 4220 is 124 dB . 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 123.6 dB and 123,8 dB respectively. No correction is required when calibrating pressure response microphones.

Adapters are available so that the B & K 1/4" and 1/8" microphones can be calibrated using the 4220. For 1/4" microphones, the adaptor DB 0310 is required. For 1/8" microphones both adaptors DB 0310 and DB 0352 are required. In each case the extra adaptors fit inside the 1/2" microphone adaptor supplied (DB 0311).

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