Hearing Aid Laboratory
This laboratory is the site of many clinical trial investigations. It houses a full double-walled sound suite, Frye Electronics 6500 probe microphone system, GS61 diagnostic audiometer, AudioScan Verifit probe microphone system, as well as five (wireless) networked computers for student and staff use. A NOAH software system with HiPRO interface provides for programming of many hearing aids for directional microphone, digital noise reduction, and feedback cancellation assessment. Multiple equalizers, amplifiers, etc., allow for generation of multi-speaker arrangements and noise sources for assessment of signal processing effectiveness.


Assembly and Repair Laboratory
Originally set up to be the "classroom" for 3:246 (Hearing Aid Assembly and Repair), this laboratory is currently used by the clinic staff for repairs and modifications as well. Because if its high reverberation characteristics (1.3 RT60), it has been the site of several studies.


Anechoic Chamber
Built in 1967, the Anechoic Chamber consists of two rooms, one contained within the other. A concrete room -- a 30 foot cube --was built onto the basement level of the Wendell Johnson Speech and Hearing Center during its construction. Inside this room, a steel walled booth is supported on steel beams attached to the floor by springs, which isolate the booth from structure-born vibration. There is a 4-inch air space on all sides between the steel booth and the concrete walls. The steel walls of the sound booth are filled with 4 inches of fiberglass insulation.

The inside of the Anechoic Chamber is treated with fiberglass wedges (3'10" in length). The fiberglass wedges are attached to the walls with wire screen in groups of three, in alternating horizontal and vertical patterns (there are about 230 wedges in all). Since all potentially reflecting surfaces must be treated, the actual "floor" of the Chamber is also treated with fiberglass; a walking surface -- about four and a half feet from the floor wedges -- is suspended to act as a support for moving around inside the chamber. A 3 foot wide expanded metal catwalk, stronger and more stable than the wire mesh, also extends into the Anechoic Chamber to support equipment.

The Anechoic Chamber is designed to be free from acoustic reflection: an-echoic. It acts as a free acoustic field for frequencies down to 60 Hz. This limitation is imposed by the configuration of the fiberglass wedges used as acoustic baffles. While is has an extremely low ambient noise level, it is not strictly speaking, "silent." The Anechoic Chamber primarily is designed for field measurements uncontaminated by reverberation and resultant standing waves. For this reason it has been the site of directional microphone measures, directivity index (DI) measures in two and three dimensions, and other investigations requiring minimal noise and reverberation.