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We have the equation:

[itex]c= \sqrt{\frac{B}{\rho}}[/itex]

Clearly since hot water is less dense, the velocity of sound is greater in hot water. But salt water is denser than fresh water, so shouldn't sound travel slower in salt water?

I have repeated the experiment over and over, but the result is the same.

The only explanation I can think of is that compared to fresh water, sea water has a greater percentage of increase in bulk modulus than in density increase. That's why sound travels faster in salt (25°C) water than hot fresh water (40-50°C). Is that right?

But isn't bulk modulus really a measure of compressibility? But salt water is harder to compress than fresh water so it has a greater B...

I appreciate it if anyone could help me understand this in a more mathematical way.