Developing a standard test method for in situ measurements of the noise reduction potential of “Quiet Rack” enclosures

摘要

ASTM E596 measures sound isolating enclosures but does not take into account either thenature of the noise source nor does it allow for the extra noise of any cooling fans that maybe part of the sound isolating enclosures. ISO 7779 measures the noise emitted bycomputers themselves and is not suitable for measuring performance of computer rackenclosure.We therefore developed a test method which utilizes a specific noise source (2U SpeakerBox) which had a spectrum similar to the typical noise generated by rack-mountedcomputer equipment and is tested in a room which has typical characteristics of an office.It is further calibrated by measuring the 2U Speaker mounted on a tripod in the positionthat will be the same as that when fitted within the enclosure. The output of the 2U Speakeris further normalized to a specific level and spectrum and the correction factor is also usedon the final measurement.This gives repeatable measurement of the (A) weighted sound pressure level, articulationindex, insertion loss and the single figure NIC based on the insertion loss. All of which canbe used to judge whether or not the measured enclosure containing a typical IT load will beacceptable in an office environment.