May 8, 2007
The National Center for Rehabilitatieve Auditory Research (NCRAR), Portland, Ore, has added the Eckel An-Eck-Oic Chamber to augment its research facilities and service the hearing health care for military veterans.
The high performance acoustic test facility was custom designed by Eckel Industries, Inc, Cambridge, Mass, to enable NCRAR to conduct a wide variety of acoustic investigations over an extremely wide range of human hearing frequencies, extending out to 20 kHz and beyond. Studies to be undertaken in the fully anechoic chamber at the NCRAR facility—a US Department of Veterans Affairs Center of Excellence—will include: hearing aid directionality and sound localization; surround-sound field research; acoustic transducer characterization and development; and characterization of loudspeaker acoustical dispersal patterns.
The chamber was engineered for outstanding, reliable acoustic performance, with special features to ensure performance that meets or exceeds acoustic standards and that acoustic integrity will be maintained over time.
The chamber has been qualified to ISO pure tone and narrow band noise standards from 150 Hz to 20 kHz and has been characterized with wide-band noise out to 100 kHz. In addition, the ambient noise levels inside the chamber have been found to be more than 5 dB lower than ISO 226:2003 Minimum Audible Field standards at all frequencies.
The NCRAR research complex is located at a subterranean elevation on the campus of the Portland VA Medical Center. The chamber was installed in a basement area that protrudes into the medical center’s garage space. Efficient and reliable isolation from outside noise, therefore, was an essential and demanding requirement. In addition, the mechanical aspect of three high pressure steam lines already running through the underground facility had to be taken into account. To ensure that these and other existing conditions would not compromise the free-fielding testing environment of the chamber, the anechoic chamber was constructed within a double-walled enclosure, with the inner room being an Eckel sound-attenuating Eckoustic Modular Panel enclosure.
The NCRAR anechoic chamber, with interior dimensions of 16 ft. x 16 ft. x 16 ft., can accommodate test equipment and the test subject. The chamber features a fiberglass wedge lining, a special cable floor, and a shielded sound double door. Custom-designed semi-acoustically transparent aluminum floor grating panels can be placed on the cable flooring if additional support for people and/or equipment is necessary. Instrumentation sleeves are incorporated into the wall and ceiling areas.
Entry into the chamber is from the adjacent 12 ft. x 24 ft. control room at floor level, which puts the bottom wedges of the chamber 7 ft. below grade. The control room is fully outfitted with stereo and 5-channel acoustic stimulus generation and analysis instrumentation, as well as stand-alone multi-channel electrical signal measurement instrumentation for both the time and the frequency domain. The chamber has two separate 24-channel high level stimulus signal amplified systems available: one, pure digital; the other, pure analog. The chamber’s interior is monitored with video cameras viewed in the control room.
Source: Eckel Industries, Inc., Acoustic Division
