"My heart maketh a noise in me: I cannot hold my peace, because thou hast heard, O my soul, the sound of the trumpet, the alarm of war."—Jer. iv.
726. Why does the tread of soldiers, when marching in long ranks, appear to be irregular?
Because the sounds proceeding from different distances, reach our ears in varying periods of time.
727. What are the numbers of vibrations in a second that produce the various musical sounds?
C or Do, 480 vibrations in a second; B or Si, 450 vibrations; A or La, 400 vibrations; G or Sol, 360 vibrations; F or Fa, 320 vibrations; E or Mi, 300 vibrations; D or Re, 270 vibrations; C or Do, 240 vibrations. It is thus seen that the more rapid the vibrations, the higher the note, and vice versa.
728. Why does the length of a wire or string determine the sound that it produces?
Because the shorter the string the more rapid are its vibrations when struck.
729. Why does the tension of a wire or string affect its vibrations?
Because when the string or wire is tight, a touch communicates vibrations to all its particles; but when it is loose the vibrations are imperfectly communicated.