Test Code vs. In-situ Sound Pressure Levels for Computers

This paper describes how computer system noise values are specified in emission sound power levels or emission sound pressure levels or both. The test code standards, such as ANSI S12.10 and ISO 7779 specify how the emission noise levels are measured and at what product operating conditions. The emission sound power level is the primary parameter that can be measured in either semi-anechoic or reverberate test rooms. It is an intrinsic attribute that is property of the product construction and operation. It is independent of the environment that it is placed in and how it is measured. Most product acoustic requirements, such as Blue Angel, are based on the declared values of the emission sound power level. The emission sound pressure level is the secondary parameter measured in semi-anechoic test rooms at the specific locations as defined in the standards. It is a rather unique specification, and its value not only depends on the product acoustic characteristics, but also impacted by the test room and measurement setup. The test room specified by the test code standards is a free field over an infinite reflecting plane, commonly referred as a semi-anechoic test room. In this environment, the floor reflects most the acoustic energy while the walls and ceiling absorb most of the acoustic energy. The requirements of the test room construction and qualification are described in ISO 3740 series. This paper presents data and compares the emission and the emission sound level under several conditions. The paper reconfirms the disclosure of the emission sound power level as the primary specification. It proposes an alternative way to better represent the end-user noise exposure through the emission sound pressure level rather than the test-code emission sound pressure level.


  • English

Media Info

  • Media Type: CD-ROM
  • Features: Figures; References; Tables;
  • Pagination: pp 994-1001
  • Monograph Title: Noise-Con 04. The 2004 National Conference on Noise Control Engineering

Subject/Index Terms

Filing Info

  • Accession Number: 01054383
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Jul 26 2007 3:10PM