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Sound power of apparatus under test is automatically measured under computer control by means of a rotating boom carrying a number of microphones supplying sound data to a digital analyzer.
English (United States)
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Automatic Sound Power Measurement
Sound power of apparatus under test is automatically measured under
computer control by means of a rotating boom carrying a number of microphones
supplying sound data to a digital analyzer.
The apparatus shown in the figure consists of a Bruel and Kjaer
3923 Rotating Microphone boom 1 carrying five microphones 2. An
adapter box 3a is connected to receive the acoustic data from the
five microphones and transmits it through boom 1. Adapter box 3
receives data from boom 1 and transmits it over individual coaxial
cables 4 to a Bruel and Kjaer 2811 Multiplexer 5. The multiplexer 5
is connected to a Bruel and Kjaer 2131 Digital Analyzer 6 and to an
IBM 5110 Computing System 7 over an interface bus 8. A signal lead
9 interconnects the analyzer 6 and multiplexer 5 and a signal lead 10
interconnects the boom 1 and multiplexer 5 via a boom control box 11.
Output data may be displayed on the screen 12 of the analyzer 6 or
may be printed by a printer 13 connected to the computing system 7.
The article 14 under test is positioned in a hemi-anechoic room
directly below the center of rotation of the boom.
In operation, a signal from the computing system 7 over bus 8 generates a
signal via multiplexer 5 to trigger a timer in control box 11 which switches on the
boom rotation motors for several seconds. Once the boom is moving, an internal
synchronizing switch controls rotation of the boom for one revolution. The boom
rotation time is adjusted to...