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.

Anonymous 0 Comments


Anonymous 0 Comments

Speed of sound in water is faster than air due to the density of the “medium” (water vs. air). As you increase depth, pressure increases and makes it denser than water at shallower depths.

Anonymous 0 Comments

I think of it as water as ball bearings.

If a square frame is packed full of ball bearings (water) you push on the edge ball bearing and nearly immediately move the opposite edge’s (In many diections probably) ball bearings. No time is expended to move the other bearings.

Less packed, (air) you would need to traverse across empty space to move edges. That takes time to traverse that empty space.

I am explaining as only “I” imagine it. Not necessarily correct analogy. Quite possibly hyperbole!🤣🤣🤣