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CHAPTER III. |
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ON RESONANCE.
37. When a sounding body causes another body to emit sound, we have an instance of a very remarkable phenomenon called resonance. The German term for it, ' co-vibration' (Mitschwingung), possesses the merit of at once indicating its essential meaning, namely the setting up of vibrations in an instrument, not by a blow or other immediate action upon it, but indirectly as the result of the vibrations of another instrument. In order to produce the effect, we have only to press down very gently one of the keys of a pianoforte, so as to raise the damper without making any sound, and then sing the corresponding note loudly into the instrument. When the voice ceases, the instrument will continue to sustain the note, which will then gradually fade away. If the key is allowed to rise again before the sound is extinct, it will abruptly cease. A similar experiment may be tried, as follows, on any pianoforte which allows the wires to be uncovered. Each note is, as is well known, |
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