PREFACE 



The reproduction of sound is so commonplace to-day that it is taken 

 for granted by the layman. Nevertheless, the developments during the 

 past two decades in the arts of communications and sound reproduction 

 have been remarkable. In the early stages of the present epoch of progress 

 the advances were made by pure scientists. As in the metamorphosis of 

 any art, the burden has been gradually shifted to the applied scientist and 

 engineer. These changes have led to a demand for expositions upon the 

 fundamental principles of the new applied science of acoustics from the 

 standpoint of the engineer. Accordingly, this book has been written with 

 the idea of presenting the elements and principles of acoustics to the 

 engineer. 



This text is the subject matter of thirty lectures prepared for presenta- 

 tion at Columbia University. It is an exposition of the fundamental prin- 

 ciples used in modern acoustics and a description of the existing acoustical 

 instruments. Particular efforts have been directed towards the develop- 

 ment of analogies between electrical, mechanical and acoustical systems, 

 because engineers have found that the reduction of a vibrating system to 

 the equivalent electrical circuit is a valuable aid in the analysis of vibrating 

 systems. These methods will become increasingly important as the front 

 of engineering acoustics is broadened. As an aid to the establishment of 

 these analogies an attempt has been made to depict a complete theme in 

 each illustration. 



The book includes the current acoustic practices in radio, phonograph, 

 sound motion pictures, public address, sound re -enforcing and sound mea- 

 surements. Practically all modern transducers such as microphones, loud 

 speakers, headphones and phonograph pickups are treated from the me- 

 chanical or the acoustical impedance viewpoint. 



A knowledge of acoustics principles is not required for an understanding 

 of the subject matter. The text may be read and understood by anyone 

 familiar with the principles of elementary physics and simple electric cir- 

 cuit theory. 



The author wishes to express his gratitude to his wife, Lorene E. Olson, 

 for assistance in the compilation, preparation and correction of the manu- 

 script. 



