xiv CONTENTS 



Chapter Page 



1 1.3 Testing of Loud Speakers 253 



A. Response Frequency Characteristic 254 



1. Response 254 



2. Apparatus for Measuring tlie Sound Pressure Frequency Re- 



lationship of a Sound Source 255 



3. Calibration of the Sound Measuring Equipment 258 



4. Outdoor or Free Space Response 259 



5. Living Room Measurements 261 



6. Theatre Measurements 261 



7. Automobile Measurements 261 



B. Directional Characteristic 261 



C. Nonlinear Distortion Characteristic 262 



D. Efficiency Frequency Characteristic 265 



1. Direct Determination of Radiated Power 265 



2. Indirect Determination of Radiated Power 266 



E. Phase Distortion Characteristic 267 



F. Impedance Frequency Characteristic 268 



G. Transient Response Characteristic 268 



H. Subjective Measurements 269 



11.4 Testing of Telephone Receivers 269 



A. Subjective Measurements 269 



B. Objective Measurements 270 



11.5 Artificial Voice 271 



11.6 Measurement of Acoustic Impedence 271 



11.7 Measurement of Noise 273 



11.8 Measurement of Reverberation Time 274 



11.9 Measurement of Absorption Coefficient 275 



11.10 Measurement of Transmission Coefficient 276 



11.11 Audiometry 276 



11.12 Articulation Measurements 277 



XII. "ARCHITECTURAL ACOUSTICS AND THE COLLECTION AND DISPER- 

 SION OF SOUND 



12.1 Introduction 278 



12.2 Dispersion of Sound 279 



A. Sound Absorption and Reverberation 279 



B. Sound Motion Picture Reproducing Systems 282 



C. Sound Re-enforcing Systems 286 



D. Reverberation Time of a Theatre for the Reproduction of Sound. . 290 



E. Power Requirements for Reproducing Systems 290 



F. Noise at Different Locations 291 



G. Public Address Systems 292 



H. General Announce and Paging Systems 296 



I. Intercommunicating Systems 297 



J. Radio Receiver Operating in a Living Room 298 



