Page:Elementary Text-book of Physics (Anthony, 1897).djvu/178

 CHAPTER II.

SOUNDS AND MUSIC.

COMPARISON OF SOUNDS.

137. Musical Tones and Noises.—The distinction between the impressions produced by musical tones and by noises is familiar to all. Physically, a musical tone is a sound the vibrations of which are regular and periodic. A noise is a sound the vibrations of which are very irregular. It may result from a confusion of musical tones, and is not always devoid of musical value. The sound produced by a block of wood dropped on the floor would not be called a musical tone, but if blocks of wood of proper shape and size be dropped upon the floor in succession, they will give the tones of the musical scale.

Musical tones may differ from one another in pitch, depending upon the frequency of the vibrations; in loudness, depending upon the amplitude of vibration; and in quality, depending upon the manner in which the vibration is executed. In regard to pitch, tones are distinguished as high or low, acute or grave. In regard to loudness, they are distinguished as loud or soft. The quality of musical tones enables us to distinguish the tones of different instruments even when sounding the same notes.

138. Methods of Determining the Number of Vibrations of a Musical Tone.—That the pitch of a tone depends upon the frequency of vibrations may be simply shown by holding the corner of