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Echoes

المؤلف:  GEORGE A. HOADLEY

المصدر:  ESSENTIALS OF PHYSICS

الجزء والصفحة:  p-201

2025-11-13

689

The repetition of a sound through reflection from any surface is called an echo. The distinctness of the echo depends upon how fully the sound is reflected, while the length of the sound that can be repeated depends upon the distance of the reflecting surface. If it takes one second to pronounce a word, and if the speaker hears the echo as soon as the word is pronounced, his distance from the reflecting surface is about 166.2 m. (one half of 332.4 m.), since in that case the sound must go from the speaker to the reflecting surface and back in one second. If a single syllable is pronounced in one fifth of a second, the surface must be at least 33.24 m. away to produce a distinct echo. There are several noted examples of echoes in the hall underneath the dome of the capitol in Washington.