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THE SCIENCE AND APPLICATIONS OF ACOUSTICS - H. H. Arnold ...

THE SCIENCE AND APPLICATIONS OF ACOUSTICS - H. H. Arnold ...

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294 12. Walls, Enclosures, and BarriersFigure 12.9. An alternative to the setup of Figure 12.8, which provides for automaticevaluation of transmission loss. The sound source can consist of a pink noise generator,filters, power amplifier, and speaker. The analyzer, which can generate random noise, canautomatically position a microphone boom for spatial and temporal averaging.provisions for automatic remote control of the microphone boom for spatial andtemporal averaging. Such an analyzer can measure in one-third octave bands thefollowing parameters: source chamber level, receiving chamber background SPL,receiving chamber SPL, and receiving chamber reverberation time.12.9 FlankingFlanking occurs when noise from a sound source is transmitted through pathsother than direct transmission through a wall between the source chamber and thereceiver on the opposite side of the wall. Among the causes of flanking are acousticalleaks through cracks around doors, windows and electrical outlets, passageof the sound through suspended ceilings with resulting reflection into adjacentrooms, HVAC (heating/ventilation/air-conditioning) ducts, floor and ceiling joists.The insulation effect of a partitioning wall is effectively decreased by flanking andacoustic leaks, examples of which are shown in Figure 12.10.12.10 Combined Sound Transmission CoefficientA wall may contain a number of elements such as windows, doors, openings,and cracks. The effective or combined sound transmission coefficient depends on

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