B Ultrasonic wave and regular sound wave

[Hesh123]

Does the speed of ultrasonic waves differ from the normal sound wave speed?
my teacher said that for normal sound wave speed v= √(γP/ρ)and for ultrasonic sound speed v= √(P/ρ) is he wrong?

 

[Baluncore]

Welcome to PF.

In air, water, or in solids?
All low-amplitude sound waves propagate at the same speed, independent of frequency.

In a gas, the speed of sound is dependent on temperature. Large amplitude sound waves, where the pressure wave can change the instantaneous air temperature, can be distorted, or become shock waves.

 

[tech99]

I think gamma here is the ratio of the adiabatic to isothermal values for specific heat capacity. I will try to find out if there is a change as the frequency increases.

 

[nasu]

is he wrong?

Yes, unless some context is missing. Ultrasound is just a name related to human hearing specifics. The formula without gamma was proposed by Newton and was latter corrected by Laplace by adding the gamma factor. The compression of air in a sound wave is better described as adiabatic rather than isothermal (as Newton assumed). The formula assumes an ideal gas, of course. In real gases there is a weak dependence of temperature and even weaker dependence on frequency.

 

[tech99]

Does the speed of ultrasonic waves differ from the normal sound wave speed?
my teacher said that for normal sound wave speed v= √(γP/ρ)and for ultrasonic sound speed v= √(P/ρ) is he wrong?

You can see from the reply by nasu #4 that your first formula applies at all frequencies.