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Altazaar OP t1_iyrqsu7 wrote

I'm asking this because I'm trying to find out what the speed of sound depends on.

I've figured out this far that it depends on the rigidity ("young's modulus") of the medium and the density.

However, now I just read that it also depends on the temperature, as vibrating molecules will have more energy to transfer onto each other.. this I do not understand.

So in case it does change.. is it because as you heat the metal it will also expand, causing the density to decrease, which should lead to a higher sound propagation?

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cuicocha t1_iz6xv41 wrote

Just a warning that the answer for "temperature effect on sound speed" will be totally different for air vs solids.

In air, sound speed depends strictly on temperature. This is because the bulk modulus of air is proportional to the pressure, so the sound speed is proportional to sqrt(pressure/density). By the ideal gas law, that means that sound speed is proportional to sqrt(temperature).

In solids, the effects of temperature on density and elastic moduli are not so simple as in gases. Also, in solids, there are both compressional and shear waves, vs just compressional waves in liquids/gases. Unfortunately, it's sometimes not clear from scientific writing on elastic waves in solids whether they're talking about compressional or shear waves (or both). In most cases I know of, higher temperature means lower elastic wave speeds because the effect on elastic modulus is stronger, especially for shear waves.

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