Holly Smith, a 2008 summa cum laude graduate of UCA, recently was awarded a NASA Workforce Development Fellowship valued at $6,500 through the Arkansas Space Grant Consortium for her project entitled, “Noise and Vibration Reduction in Ventilation Systems.” Her work was conducted at the Johnson Space Center in Houston, Tex. during ten weeks this summer.
Smith plans to begin work toward her Doctorate in Acoustics at Pennsylvania State University. While at UCA, she investigated the acoustic properties of a low pitch sound source with Dr. William V. Slaton. The pitch of the sound produced is dependent on the shape of the acoustic resonator; in this case a large volume connected to a short open tube. Sound is produced via thermal interactions between the air and a porous ceramic substrate located in the tube that supports a temperature difference. At sufficiently large temperature differences, the system will spontaneously produce loud sound with no moving parts! The phenomenon that generates sound using heat in this manner is known as thermoacoustics. Previous work in thermoacoustics has focused on resonators that were straight pipes, similar to organ pipes or flutes, which support a different array of resonance frequencies from that in Smith’s work.This type of resonator is also used in acoustic noise control in ventilation systems. The insertion of a porous substrate acts to increase the damping of certain frequencies. The ventilation system aboard the International Space Station is a crucial life-support system that provides the crew with circulated, filtered air; however, this system often contains fans that generate unwanted noise and vibrations. The amount of noise generated by these fans must be brought down to an acceptable level so the astronauts can live and work comfortably.
The Acoustics Office at the Johnson Space Center evaluates space hardware for compliance with acoustic noise limits. Smith worked with director Chris Allen, as well as the other scientists and staff to identify noisy equipment and design acoustic mufflers to minimize the noise.
