BRUEL & KJAER 4220 - Description of the Pistonphone; General Description

Description
General.
The Pistonphone Type 4220 (Fig. 2) is of cylindrical shape with small
dimensions (comparable with the dimensions of a "flash light"), and is
battery operated. It is consequently compact and portable, always ready for
use, having no mains connections, and can be utilised under the most
difficult ambient conditions. Once the microphone is fitted to the coupler the
operation consists simply of starting the pistonphone and adjusting the
sensitivity of the components in the sound measuring equipment until the
deflection
on the indicating instrument corresponds to the S.P.L. (RMS
Sound Pressure Level) produced by the pistonphone.
Fig. 2. P holograph of the Pistonphone.
Each pistonphone is individually calibrated and the exact value of calibration,
which can deviate a few tenth of dB from the nominal 124 dB, is indicated
on the calibration chart which is supplied with the instrument upon delivery.
The calibration is given at normal atmospheric pressure (760 mm Hg). The
maximum error of calibration is less than ± o.2 dB.
(66(22
Fig. 9. Assembly drawing of the Pistonphone.
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