The strain-energy release rate is determined for an edge crack in a uniformly stressed bar o f circular cross-section. Values o f the strain-energy release rate, obtained using a finite-element representation o f the bar and by measuring the compliance of the bar experimentally, are shown to be in close agreement. For crack depths of less than one-half diameter. the strain-energy release rates are found to be lower than existing results on rectangular bars having the same relative crack length. / Crack P A a =t t i t t 7

A study was conducted to investigate the relationship between preferences in automobile exhaust noise and the demographic factors of a listening jury. Noise samples of four different vehicles were recorded at idle as well as at 3000 RPM, and 1/3 octave sound spectra were acquired simultaneously. The recordings were presented to the jury using headphones and a preference survey was administered. Zwicker loudness was computed for all samples. Demographic factors such as gender, age, current and future vehicle ownership, were correlated to listening preferences, and unforeseen results were found, especially in regards to sport utility vehicles (SUV).

The replacement of a Sitka spruce grand concert harp soundboard with a carbon fiber-reinforced plastic soundboard could provide improved durability and long-term stability. Experimental vibratory studies on concert harps with wooden soundboards are reviewed. A computational finite-element model is used to identify critical material properties by matching its predictions to the experimental data. With the material properties identified in the finite-element model, the lay-up of the composite soundboard is created using matching criteria based on research of wood replacements for violin top plates. The composite lay-up is then incorporated into the finite-element model, verifying that the dynamic response closely approximates that of the wooden soundboard. The identification technique and composite replacement design process may be applicable to other musical instruments, as well as other nonmusical, wooden plate structures.

The Audio Arts and Acoustics department at Columbia College in Chicago acquired a new building in 2003. The facility, a former bank, contained an old steel and concrete vault that was converted to a reverberation chamber. The acoustic properties of the space, including reverberation time, modal density, and early reflection maps were analyzed and compared to a computer model. Reflectograms were predicted at various locations and compared to test data acquired with Time Delay Spectrometry (TDS). Polar Energy Time (PET) techniques were also used to identify the location of a single 4×4 sample of foam absorber and the results of the test were compared to the predicted value from the computer model. The results of the tests show that, under its current configuration, the room is usable as a reverberation chamber down to 300 Hz, and that the computer model was able to accurately predict the results from the PET methodology.

Nine small volume classrooms in schools located in the Chicago suburbs were tested to quantify speech intelligibility at various seat locations. Several popular intelligibility metrics were investigated, including Speech Transmission Index (STI), %Alcons, Signal to Noise Ratios (SNR), and 80 ms Useful/Detrimental Ratios (U80). Incorrect STI values were experienced in high noise environments, while the U80s and the SNRs were found to be the most accurate methodologies. Test results are evaluated against the guidelines of ANSI S12.60-2002, and match the data from previous research.