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What makes two sounds similar?

  1. Feb 12, 2012 #1
    what makes two sounds similar???

    i have been wondering this for a long time...

    for example:
    if we say the word "hello" with a loud pitch scientifically speaking higher amplitude
    if we say the word "hello" with a low amplitude
    if we say "hello" really fast
    if we say "hello" very slow
    if we say "hello" normally

    the question:
    what make all the above sounds similar?? as in if we graph the above sounds what would remain constant in all the graph??

    thank you
  2. jcsd
  3. Feb 12, 2012 #2
    Re: what makes two sounds similar???

    Wikipedia has this to say:


    But the thing that REALLY makes them similar is that all sound is a longitudinal wave....
    the above referenced articles discusses this....Light, in contrast, is transverse.
  4. Feb 12, 2012 #3


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    hello anj16! :smile:
    the shape

    it'll always be the same, except it may be higher or lower on the page, or stretched or squeezed horizontally and/or vertically :wink:
  5. Feb 12, 2012 #4


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    Re: what makes two sounds similar???

    anj16, Welcome to Physics Forums! It is important that we all use terms accepted by science to describe experiments. Otherwise, folks will be confused as to our meaning and miss the point. For example, the term "amplitude" is quite different from the term "pitch".
    As for your question in the OP, there are similiarities in those examples you gave. They are described by "acoustic signature". Just Google that and see the Wikipedia page plus references. In classifying and identifying particular ships and submarines and also in identifying specific species of birds and frogs we use an "acoustic fingerprint". Google that, too.
  6. Feb 12, 2012 #5


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    Re: what makes two sounds similar???

    pitch (frequency)
    amplitude (loudness)
    tone/envelope (shape)
    harmonics (multiple sounds)

    For all your sounds, the first two can vary, but it is the third - the tone - that makes them all sound similar.

    Alternately, you could keep the pitch and amplitude the same and change the tone, to get sounds that are very different.

    Say the word 'woah' very slow, 'w' then 'o' then 'ah'. The major difference between the three is the tone of the sound.

    Tone is the shape of each individual peak/valley. There are sine waves, sawtooth, square waves etc. The wider the shape (within the cycle), the more round the tone (like 'o'). The thinner the shape, the thinner the sound (like 'w').

    See here. There's a little audio clip on the right.

    There are other factors, such as harmonics, that play into the 'sound' of sound.
  7. Feb 13, 2012 #6


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    Re: what makes two sounds similar???

    If you wonder what makes them all be understood the same way - that is, why we hear "hello" each time, and not some other random word - check Liberman-Mattingly motor theory of speech perception (and related theories).
  8. Feb 13, 2012 #7
    Re: what makes two sounds similar???

    Thank you all for helping me out

    just to clarify DaveC426913 would i be consistent with your explanation if i say that the number of peak and valleys remain constant making the sounds sound similar???
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