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como e que e possivel o timbre depender da forma das vibrações (How is it that it is possible for the pitch to depend on the shape of the vibration / wave?)
- JOANA FREITAS (age 13)
colegio rainha santa isabel, coimbra
The pitch depends on how often a particle vibrates when a wave passes
through, otherwise known as the frequency of the wave. How often does
the pressure vary from high to low and back again? The higher the
frequency (more vibrations), then the higher the pitch will be; the
lower the frequency (less vibrations), the lower the pitch will be.
Since frequency is the reciprocal of the period, the higher the
frequency the more peaks and valleys within a given amount of time.
Because sound waves in air travel atabout the same speed regardless of
their frequency, high frequency also means more peaks and valleys in a
a spatial picture of the sound wave. In other words, the wavelength of
the high-frequency waves is shorter tha of low-frequency waves. Sorry,
I don't know how to insert an image, but there is a great website where
you can see the different shapes of the waves in high and low pitches
(frequencies) at: http://www.glenbrook.k12.il.us/gbssci/phys/Class/sound/u11l2a.html
(republished on 07/29/06)
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