If salinity increases, what happens to the speed of sound in water?

If salinity increases, what happens to the speed of sound in water?

• A. Decreases
• B. Increases
• C. Remains the same
• D. Depends on depth

Answer: (B)

Increasing salinity makes seawater stiffer to compression, which raises the bulk modulus more than it raises density. Since sound speed in a liquid is tied to how easily it compresses (c^2 ≈ bulk modulus divided by density), a higher bulk modulus leads to a faster propagating pressure wave. So, at a given temperature and pressure, more dissolved salt speeds up the sound. Temperature and depth also affect speed, but the direct effect of increasing salinity is to raise the sound speed.

Increasing salinity makes seawater stiffer to compression, which raises the bulk modulus more than it raises density. Since sound speed in a liquid is tied to how easily it compresses (c^2 ≈ bulk modulus divided by density), a higher bulk modulus leads to a faster propagating pressure wave. So, at a given temperature and pressure, more dissolved salt speeds up the sound. Temperature and depth also affect speed, but the direct effect of increasing salinity is to raise the sound speed.