If you
go near to a harp or a piano, and sing any particular note very
loudly, you will hear this note sounding in the instrument,
because you will set just that particular string quivering, which
gives the note you sang. The air-waves set going by your voice
touch that string, because it can quiver in time with them, while
none of the other strings can do so. Now, just in the same way
the tiny instrument of three thousand strings in your ear, which
is called Corti's organ, vibrates to the air-waves, one thread to
one set of waves, and another to another, and according to the
fibre that quivers, will be the sound you hear. Here then at
last, we see how nature speaks to us. All the movements going on
outside, however violent and varied they may be, cannot of
themselves make sound. But here, in the little space behind the
drum of our ear, the air-waves are sorted and sent on to our
brain, where they speak to us as sound.
Week 18
But why then do we not hear all sounds as music? Why are some
mere noise, and others clear musical notes? This depends
entirely upon whether the sound-waves come quickly and regularly,
or by an irregular succession of shocks.
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