Browsing by Subject "Public address systems--Computer simulation"
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Item Improving speech intelligibility with a constant-beamwidth, wide-bandwidth loudspeaker array(2006) Winker, Douglas Frank; Becker, Michael F.; Hixson, Elmer L.This dissertation covers the topic of improving speech intelligibility with a constant-beamwidth, wide-bandwidth (CBWB) loudspeaker array. The concept is examined through computer simulation, array implementation, and field tests. A review of speech, speech intelligibility, and the methods used to evaluate speech intelligibility are presented. The concepts of reverberation and RT60 are presented along with a discussion of the direct-to-reverberant ratio (D/R) and how it is affected by the source’s Q. The first part of this work was conducted via computer simulations. The CATT-Acoustic software package was used to simulate the rooms used in this study and to determine the optimum beam pattern for the array. The simulations compare the performance of the array to the performance of a typical PA source and show that the array decreases the D/R and improves speech intelligibility. Array theory is presented and the concept of a CBWB array is developed. First, basic array theory is reviewed for an N-element broadside array. Next, the concept of array element superposition is discussed. The filter weighting functions for the CBWB array are developed and analyzed. Finally, the directivity function for a crossed array is examined. A thorough discussion of the array’s design is given along with justification of the design procedure. An overview of the physical construction is given and a modeled version of the array is introduced. The linear-phase, FIR digital filters are developed from theory for each band of interest and the implemented filters are compared with their theoretical counterparts. Finally, the field test results are presented and compared with the simulation. The model array was tested in the anechoic chamber to verify the design. The results are compared to the design parameters and the design is confirmed. Next, the full array was tested in two locations and compared with a typical PA source. As predicted, the array increases the speech intelligibility in the rooms and increases the D/R.