A COMPARISON OF SOURCE TYPES AND THEIR IMPACTS ON ACOUSTICAL METRICS By KEELY SIEBEIN A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN ARCHITECTURAL STUDIES UNIVERSITY OF FLORIDA 2012 1 © 2012 Keely Siebein 2 To my parents 3 ACKNOWLEDGMENTS I would like to thank my mother, father, sisters, brothers, nephews and the rest of my family for all your love and support throughout my life. I would like to thank Professors Gold and Siebein for your continuous support, guidance and encouragement throughout the process of my thesis. I’d also like to thank my fellow acoustics students, Sang Bong, and Sang Bum, Cory, Adam B, Adam G., Jose, Jorge and Jenn and any others who helped me with the data collection and reviewing of the material and for keeping me on track with the process. I’d also like to thank Dave for your continuous support throughout this entire process, for believing in me and doing all that you could to help me throughout the course of my studies. I’d also like to thank my wonderful friends, for believing in me and encouraging me throughout my studies. Thanks to my Dad, for being my father, professor, boss, but most importantly, my mentor. It’s an honor to have studied with you and learned from you in this capacity and I will treasure these years and the time I spent learning under your guidance forever. Thank you all for everything. 4 TABLE OF CONTENTS page ACKNOWLEDGMENTS .................................................................................................. 4 LIST OF TABLES ............................................................................................................ 7 LIST OF FIGURES .......................................................................................................... 8 ABSTRACT ................................................................................................................... 15 CHAPTER 1 INTRODUCTION .................................................................................................... 17 2 LITERATURE REVIEW .......................................................................................... 19 Architectural Acoustics............................................................................................ 19 Fine Structure of Reverberation .............................................................................. 22 Impulse Response .................................................................................................. 24 Overview .......................................................................................................... 24 Comparison of the Early and Late Portions of the Impulse Response. ............ 26 Acoustical Criteria ................................................................................................... 29 Reverberation ................................................................................................... 29 Early Decay Time ............................................................................................. 30 Clarity/Intelligibility ............................................................................................ 30 Diffuse Sound Field .......................................................................................... 32 Soundscape Theory ................................................................................................ 33 Worship Space Acoustics ....................................................................................... 36 Performance Space Acoustics ................................................................................ 37 Balloon Pop Study .................................................................................................. 38 Omnidirectional Speaker Study .............................................................................. 38 Directivity of Sources .............................................................................................. 39 Reverberation Time: Traditional Equations and Acoustical Standards ................... 41 Traditional Equations ........................................................................................ 41 Acoustical Standards ........................................................................................ 43 ISO 3382 .................................................................................................... 43 ASTM E 2235 ............................................................................................. 44 Just Noticeable Differences in Acoustical Metrics ................................................... 45 Reverberation Time .......................................................................................... 45 Early Decay Time ............................................................................................. 46 Clarity (C80)....................................................................................................... 47 3 ACOUSTIC SOURCE COMPARISON STUDIES ................................................... 49 General Information ................................................................................................ 49 Floor Plan ............................................................................................................... 49 5 Reverberation ......................................................................................................... 49 Materials ................................................................................................................. 50 Pilot Study ............................................................................................................... 50 Method ............................................................................................................. 51 Electronic Signal Results .................................................................................. 51 Natural Acoustic Signals................................................................................... 54 Anechoic voice and music as measurement sources ................................ 55 Live music as a measurement source ........................................................ 55 Balloon pop as a measurement source ...................................................... 56 Results ............................................................................................................. 56 Pilot Study Conclusions .................................................................................... 58 Source Signal Comparison ..................................................................................... 59 Method ............................................................................................................. 59 Study 1: Omnidirectional, Directional and Calculated Comparisons ................. 60 Electronic signals ....................................................................................... 61 Reverberation time ..................................................................................... 61 Clarity (C80) ................................................................................................ 65 Study 2: Anechoic Music and Speech and Balloon Pop Stimuli Comparison ... 68 RT Comparison ................................................................................................ 76 RT – EDT Comparison ..................................................................................... 78 Natural acoustic sources ............................................................................ 78 Scientifically calibrated sources ................................................................. 88 Reverberation Time Comparison Results ......................................................... 89 Early Decay Time Comparison Results ............................................................ 96 C80 Comparison Results ................................................................................. 102 Just Noticeable Differences ............................................................................ 106 Reverberation time just noticeable differences ........................................ 107 Early decay time just noticeable differences ............................................ 109 Clarity (C80) just noticeable differences .................................................... 112 Discussion ...................................................................................................... 115 Conclusions .................................................................................................... 116 Future Studies ................................................................................................ 129 APPENDIX A IMPULSE RESPONSE PRINTOUTS FOR WIN MLS SOURCES ........................ 130 B OMNIDIRECTIONAL AND DIRECTIONAL LOUDSPEAKER COMPARISON ...... 140 LIST OF REFERENCES ............................................................................................. 146 BIOGRAPHICAL SKETCH .......................................................................................... 149 6 LIST OF TABLES Table page 3-1 Just noticeable difference in reverberation time ranges grouped by method .... 107 3-2 Just noticeable difference in reverberation time ranges grouped by receiver position ............................................................................................................. 109 3-3 Just noticeable difference ranges for early decay time grouped