. Echoes of bats and men . Fig. 6. A graph of the sound pressure in a very short word without any echo is shown in A, and the same word with echoes is shown in B. Note the similarity of the early waves in A and B, and a difference as the echo returns before the original word has ended. good fraction of a second after the end of the sound that came directly from a speaker's mouth. Such photographs also show clearly the greater magnitude of the echoes that follow the same word spoken indoors rather than out. An example of this comparison is seen in Fig. 6, but 61

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Keywords: ., bookcentury1900, bookcollectionbiodivers, booksubjectorientation