Traditional And Angle-dependent Characterization Of Penn State’s Panel Transmission Loss Suite

Open Access
Author:
Bauch, Paul Francis
Graduate Program:
Acoustics
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
June 14, 2013
Committee Members:
  • Stephen A Hambric, Thesis Advisor
  • Andrew Barnard, Thesis Advisor
Keywords:
  • Transmission Loss
  • Structural Acoustics
  • Room Acoustics
  • Acoustics
  • Anechoic
  • Reverberant
  • Beamforming
Abstract:
The Center for Acoustics and Vibration at Penn State has a Panel Transmission Loss Suite consisting of a reverberation chamber coupled to an anechoic room. This facility has multiple applications in sound attenuation metrics and sound radiation analysis. The facility was characterized to determine the performance and limitations of the space. The reverberation chamber was previously characterized according to ASTM C423-02a, with a cutoff frequency at 630 Hz and reverberation times from 3 to 7 seconds. The anechoic room has been characterized according to ISO 3745 (2003) over the frequency range of 160 Hz to 10 kHz. The room behaves hemi-anechoically over this frequency range and meets the allowable deviation from the inverse square law for hemi-anechoic environments. Flanking transmissions have been measured according to ASTM E2249 and E90, limiting transmission loss measurements to 40 dB at the 400 Hz one-third-octave band increasing to 55 dB at the 10 kHz band. The diffusivity of the incident sound field at the transmission aperture, or “niche”, has been investigated using beamforming and spatial correlation techniques. Transmission loss measurements suggest near-normal-incidence plane waves at frequencies below 1 kHz transitioning to more random of ‘field’ incidence at frequencies above 1 kHz. Potential diffusivity metrics at the “niche” are discussed based on these measurements. The Spatial Correlation Assurance Function (SCAF) is introduced to quantify incident field diffusivity in transmission loss facilities. Deviations in the sound pressure level at the transmission aperture from the averaged sound pressure level in the source room may be used to correct the non-diffuse field bias in lower frequency bands.