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Sound and Vibration Instrument Hire and Calibration

Bruel & Kjaer 4231 Sound Calibrator - Class 1

B&K 4231 Sound Level calibrator
B&K 4231 : Sound Level Calibrator - class 1 £ 3 a day *

For calibration of sound level meters and other sound measurement equipment

Conforms to IEC 942 Class 1 and BS 7189 Class 1
Robust pocket-size design with highly stable level and frequency
Calibration accuracy ±0.2 dB
94 dB or 114 dB SPL for calibration in noisy environments
Extremely small influence of static pressure
Sound pressure independent of microphone equivalent volume

The Sound Level Meter 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 Bruel & Kjaer 1" and 1/2" microphones and, with adaptors, it can be used for 1/4" microphones as well.

The calibration frequency is 1000 Hz (the reference frequency for the standardized 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 μPa is equal to 1 Pa or 1N/m2. The +20 dB level step gives 114 dB SPL which is convenient for calibration in noisy environments.

The design of the 4231 is based on a feed-back arrangement to ensure a highly stable sound pressure level and ease of use. The feed-back loop uses a condenser microphone, which is specially developed for this purpose. This microphone is optimised to have extremely high stability and independence of variations in static pressure and temperature around the 1 kHz calibration frequency. The result of this is a user-friendly calibrator where exact fitting of the microphone is non critical and the effects of changes in temperature and static pressure are negligible.

The calibrator gives a continuous sound pressure level when fitted on a microphone and activated. The sensitivity of the sound measuring equipment can then be adjusted until it indicates the correct sound pressure level. The calibrator is automatically switched off when removed from the microphone.

Includes a leather protecting case, which does not need to be removed to use the calibrator.

Manufacturer's Specifications.

See other Sound Level Calibrators, available for hire.

* Our standard hire charges are based on a 4-day minimum period, details other options.

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