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Special Microphones for Sound Intensity Measurements

Special pairs of microphones are produced for use in sound intensity probes. These microphones are similar in most respects to other measurement microphones — except that these matched pairs are selected to have similar open-circuit sensitivity, frequency- and phase-response characteristics. Since measuring intensity is essentially measuring the instantaneous difference in the sound pressure at two close points in space, it is essential to minimize any differences the microphones might introduce.

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  1. Microphone pairs for sound intensity — matching specifications
  2. Vent sensitivity of special microphones
  3. Other special microphones

Brüel & Kjær matched pairs are easily identified by the small 'screw studs' on their diaphragm protection grid. These are used to secure the microphone spacer which is part of the sound intensity probe assembly. The two microphones in the matched pair are additionally labeled Part 1 and Part 2 respectively. The two parts are uniquely matched and should always be kept together.

There are both 1/2" and 1/4" matched microphones. 1/2" matched pairs are the most popular choice for general sound intensity measurements. 1/4" matched pairs are selected for high-frequency sound intensity measurements and use in side-by-side probe assemblies. The side-by-side arrangement enables the microphones to be used much nearer to a source than the more common and more acoustically ideal face-to-face probe assembly.

Microphone pairs for sound intensity

Microphone pairs for sound intensity — matching specifications

Amplitude-response difference, normalized at 250 Hz

Phase-response difference (or 'phase matching')

Vent sensitivity of special microphones

Brüel & Kjær phase correctors

Other special microphones