• Question: Do sound waves travel forever?

    Asked by smithmoorebell to Ben, Clare, Ezzy, Mario, Sam on 12 Mar 2012.
    • Photo: Mario Campanelli

      Mario Campanelli answered on 12 Mar 2012:

      well, there is friction in air, and it reduces the amplitude until they fade completely. Not to talk about the fact that sound waves emitted by a point source have an intensity decreasing like the square of the distance (like gravity, or electrostatics)

    • Photo: Ben Smart

      Ben Smart answered on 12 Mar 2012:

      Sound waves are just vibrations. As sound waves travel further and further they get quieter and quieter (the vibrations get smaller). Eventually the sound waves will be so quiet that you wouldn’t even call them sound waves (the vibrations would be so small you wouldn’t be able to tell them apart from atoms vibrating due to heat energy). So the energy from sound waves will carry on moving about, but as for a sound you could hear, no that wouldn’t travel forever.

    • Photo: Elizabeth Pearson

      Elizabeth Pearson answered on 12 Mar 2012:

      As a wave goes out it spreads out and gets weaker for a given point on the wave (the total energy of the wave stays the same, but the front is bigger). Eventually it gets so weak you can’t detect it anymore so eventually it will dissipate away.

      There’s also the issue that once you get to space there’s nothing to carry the sound any more. So it can get there, and then it goes no further.

    • Photo: Clare Burrage

      Clare Burrage answered on 18 Mar 2012:

      If there is no friction then they could travel forever. Unfortunately sound waves can only travel through substances like the air and water which do have friction, so in reality no sound wave travels forever.

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