Model CAL291

Under IEC and ANSI standards, a sound intensity measuring system consists of a two microphone sound intensity probe and a dual channel processor. The accuracy of the intensity measurement is strongly dependent upon the phase accuracy between the two measurement channels, including the microphones. Sound intensity measurement systems are classified into Class 1 or 2 based upon the pressure-residual-intensity index which is measured using a residual intensity testing device. For direct calibration or verification of the accuracy of a sound intensity measurement system, IEC 1043 and ANSI S1.9 call for the use of a sound intensity calibrator which delivers to the probe microphones the simulated intensity at a specified temperature, atmospheric pressure and nominal microphone separation.

The Larson Davis Model CAL291 Residual Intensity Calibrator satisfies the residual intensity test device specifications of both IEC 1043:1993 and ANSI S1.9-1996.

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Testing of sound intensity measurement systems

Generation of signals for verification of the  amplitude/phase accuracy of multi-channel acoustic measurement systems

Amplitude/Phase Normalization. The digital filters of the Larson Davis 3000+ analyzer provide both amplitude and phase, permitting the measurement of the complex transfer function between two measurement channels, including microphones, in 1/3 octave bands by using the CAL291 to excite both microphones with broadband noise. From this a correction function can be generated within the analyzer to correct for any amplitude and phase errors which may have existed between channels previous to the normalization procedure.

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Applies the same signal with zero phase difference to a pair of 1/2" or 1/4" microphones

Driven by external signal generators such as the following versions available with the Larson Davis Models 2800/2900 and 3200 Real-time Analyzers:

OPT 10 Noise Generator; pink or white broadband noise

OPT 11 Digital Signal Generator; Sinusoidal, pink or white broadband noise, 1/3 octave bandlimited pink pseudo random noise and white pseudo random noise

Amplifier provides signal levels to 127 dB

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Documentation

CAL291 Residual Intensity Calibrator

 

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