Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: Acoustics The transmission and reflection of sound waves has now been reduced to a matter of exact scientific knowledge, and we are able accurately to solve the problem of acoustics as governed by known conditions. In other words, we now know under just what circumstances a sound wave may be projected a maximum distance; under what conditions it will be muffled, deadened or destroyed, and this knowledge enables us to secure good acoustic properties in the erection of a theatre. A sound wave starts at the origin of the sound and expands in all directions until either lost by constantly diminished power, or reflected, as a ray of light would be, into other directions until diminished to inaudibility. Thus, the sound originated on the stage strikes the ceiling, walls and boundaries of the space within the auditorium, and is reflected from these surfaces to the ears of the audience. A certain portion of the expanding sound wave reaches the ear directly, without reflection. It is essential that the direct wave, or spoken word transmitted as sound, reach the ear at the same time as the reflected wave or word. If it does not do this, then the sound or word is broken into twoor more bits, each reaching the ear an infinitesimal fraction of time apart, with the result that the word is confused, difficult to understand or to hear clearly. The ear is not sensitive enough to catch the distinct separation of these waves, except in case of a pronounced echo, but does appreciate that the sound has become muffled, indistinct and hard to "understand." To make this still more clear, let us assume that a pistol is fired on the stage. The sharp report radiates from its source in every direction; that going backward is reflected out front by the back wall or the scenery; some goes up (if there...