Page 22 - Winter 2009

Fig. 13. Inside the completed chamber.
free field for frequencies ≥80 Hz at a distance of 2 m, which met the chamber’s design specification. The free-field traverse data for 100 Hz and 80 Hz are shown in Fig. 12. The chamber’s free
field also accommodates a 3.6 by 3.35 by 3.0 m (L x W x H) par- allelepiped for ISO 3744:1994 (Determination of sound power levels of noise sources using sound pressure—Engineer-ing method in an essentially free field over a reflecting plane) noise testing. The completed chamber is shown in Fig. 13.
Conclusion
Several challenges arose during the design and construc- tion of this project. The low-noise requirements, chamber flexibility, and free-field performance each provided a unique set of challenges. The chamber has been in operation since January 2008 and has tested a wide range of specimens. It has proved to be successful at meeting each of its design goals and has proven useful in the development of new sources for hemi-anechoic chamber qualification and free-field per- formance research. Due to the upfront planning and engi- neering, the chamber will continue to be a useful tool well into the future regardless of infrastructure growth and expansion in the area.AT
Douglas F. Winker is the principal acoustic engineer for ETS-Lindgren. He oversees the design of all of ETS-Lindgren’s acoustic chambers, acoustics projects, and research and development. Doug received a Ph.D. in Acoustics from the Department of Electrical and Computer Engineering at The University of Texas at Austin, and holds a patent for a sound source used in anechoic chamber qualification. He is a member of the Acoustical Society of America, the Audio Engineering Society, the Institute of Noise Control Engineering, the Institute of Electrical and Electronics Engineers, and the Phi Kappa Phi honor society.
Low-Noise Hemi-Anechoic Chamber 21