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Quality of sound

  1. Dec 5, 2006 #1
    what does the soundwaves of a poor quality sound look like??
    and richer quality?
     
  2. jcsd
  3. Dec 5, 2006 #2
    "Higher" quality sound has (in general) more harmonics than poorer sounding sound. For instance, an orchestra can produce a richer sound than an electric guitar even though they may be just as loud. There are a lot of details like how the harmonics work together, etc, but in general that is the difference.

    So if you take a FFT of the orchestra, you will see a lot of small spikes at a large number of frequencies in addition to the larger spikes while the guitar would have a much simplier spectrum.
     
    Last edited: Dec 5, 2006
  4. Dec 5, 2006 #3
    so in terms of how the soundwaves look like,
    higher quality soundwaves have rippled sort of lines with a lot of frequencies and poor quality soundwaves have smooth lines of waves with less frequencies?
     
  5. Dec 5, 2006 #4

    sas3

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    Well, if you have clipping (sounds very bad) it just looks like the peeks are cut off.
     
    Last edited: Dec 5, 2006
  6. Dec 5, 2006 #5
    I'm not quite sure about what you mean by "the peeks are cut off". :confused:
     
  7. Dec 5, 2006 #6

    sas3

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    Here are some pictures to help explain it.
    [​IMG]

    [​IMG]
     
  8. Dec 6, 2006 #7

    turbo

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    If you run a sinusoidal signal through a solid-state amplifier (look at sa3's graphs) the amplifier will produce it very accurately until you try to increase the volume past the capacity of the amplifier. At that point (and thereafter) the amp will "clip". It will not be able to reproduce the entire waveform, so the peaks (the most positive and negative excursions) will have flat spots (clipping) with very sharp transitions (the squared-off corners) that sound very harsh. Tube-driven amplifiers do not clip as sharply, and have a more complex waveform when they do clip, so they are more pleasant to listen to when overdriven. When you listen to Angus Young (AC/DC), Eric Clapton, Stevie Ray Vaughan, or almost any other top guitarist, you are listening to them performing on tube amps - the complexity of the tone is essential to their distinctive sounds. There are a few top guitarists who use solid-state amplifiers, like BB King, but they are in a very distinct minority.
     
  9. Dec 6, 2006 #8
    If you are talking about digital sound then, as well as the clipping effects, the quality depends on the compression level and format used. In general as the quality gets lower then artefacts will begin to become more prominent in the waveforms which can often be heard as clicks, pops or chirps of all sorts given sufficiently bad quality, the exact type of artefact will depend on the compression method employed.

    If there is no compression and it is just plain wave data then the quality loss will come from clipping as above, but also from the discrete representation used for the waves, in theory at low enough bit rates you could end up with a nasty irregular jaggy triangle wave from a perfect sine wave.

    Another source of poor quality is noise from the recording. A hissing noise usually looks like lots of tiny and rapid changes in the waveforms. Its quite difficult to seperate noise from the details of a high quality recording sometimes, although in general most noise is so far up the frequency spectrum that you can get more than acceptable results by cutting off frequencies above some cut off point... i.e. a low-pass filter
     
    Last edited: Dec 6, 2006
  10. Dec 6, 2006 #9

    sas3

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