Does sound have higher frequency/wavelength in water?

[Padfoot]

(Compared to air)

I know there is an equation calculating speed of sound waves in various medium, but I was just thinking how v = f*wavelength, so since sound travels faster in water, shouldn't that mean that the frequency or wavelength of the sound in water is also higher?

Question #16 of TBR's sound section was comparing bat sonar to underwater sonar. The speed of sound underwater is 1500m/s, much higher than the 330 m/s in air, so that's why I assumed that bat sonar must have a longer wavelength or higher frequency, but it actually has a shorter wavelength.

Can someone explain why my thinking is wrong?

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[sillyjoe]

V = (Wavelength) * (Frequency)

As a wave enters a more dense medium the velocity increases while the frequency remains constant. Therefore when going from air to water (relatively more dense) the velocity increases and as a result, the wavelength increases.

Bat sonar has a velocity of 330 m/s and the speed of sound underwater is 1500 m/s. Since V = (wavelength) * (frequency) and we know the frequency must remain constant, then the wavelength will be more (bigger) in water and less in air because the velocity is higher in water than in air.

 

[Padfoot]

Thanks! but how do we know that the frequency is constant, since a bat and a submarine probably release waves of different frequency?

 

[sillyjoe]

The frequency remains constant for a given sound wave when it changes medium.