The art of sound pictures (1930)

236 THE ART OF SOUND PICTURES gradually being eliminated by perfection of the electrical apparatus and the technique of recording sound. In the first few sound pictures, very little difference could be detected between the voices of the men and those of the women. The principle of resonance, which plays a great part in all music, speaking, and theatrical acoustics, is simply this. If you have a column of air contained in a wooden box, such as the box of a violin, for example, you have what is called a resonator. The shape and quantity of the air column will cause it to vibrate sympathetically with certain musical tones. These S5mipathetic vibrations of the air column have the effect, in turn, of increasing the tones with which they vibrate. There is a laboratory instrument of this sort which can be set so that the air column within it corresponds precisely to a given note. By placing this resonator to the ear, one can pick a single note out of a complex orchestra number, so that the single note is all one hears. In the same way, sound recording apparatus tends to be selective. It tends to pick out certain notes and certain octaves of tone and to favor them in the sound records, as against other tones and other octaves. Thus, a woman’s voice in the early sound pictures was recorded either as a squeak, or as a deep voice, similar to that of a man. The principle of resonance was responsible. The sound recording and transmitting apparatus tended to select certain tones to the exclusion of others. This difficulty, also, has now been corrected to a great extent, and improvements are going forward rapidly in all the sound laboratories of the big producing companies. The refinements of electrical apparatus whereby these