Why does the speed of sound in water increase with pressure?

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I’ve heard some explanations before which just sound intuitively wrong – mostly that “higher pressure = higher density = particles closer together = easier propagation of pressure wave”. I don’t like this firstly because water is only negligibly compressible and also because a higher density would surely lead to a lower speed of sound ceteris paribus?
Happy that speed of sound is a function of bulk modulus but can’t wrap my head around why the bulk modulus would be different at different pressures. Thanks for any help!

In: Physics

4 Answers

Anonymous 0 Comments

The Chin-Millero equation (according to my internet search) predicts that
Going from 10m depth to 5000m depth at 40C
Increases speed of sound from 1570 to 1640 m/s for 4.4% increase.
(Also, salinity and temperature are much bigger factors.)

So I think your logic is sound that water density does not change much. However, that pressure change is a staggering 508x increase. (50 MPa)

4.4% doesn’t seem so big in comparison.
Huge condition change made a small noticeable difference.

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