# Sound wave intensity

The velocity of sound in air of density rho=1.29 kg/m^3 may be taken to be 330m/s. Show that the acoustic pressure for the painfull sound of 10 W/m^2 ~ 6.5x10^-4 of an atm. (atm~10^5 N/m^2)

What is acoustic pressure. This question is easy I am sure, but I dont really know what it is asking for. I have read and re-read the chapter on sound waves, but I dont see any term defined as acoustic pressure. I am guessing it is the "overpressure", but I dont know of a relationship between overpressure and Intensity.

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OlderDan
Homework Helper
silverdiesel said:
The velocity of sound in air of density rho=1.29 kg/m^3 may be taken to be 330m/s. Show that the acoustic pressure for the painfull sound of 10 W/m^2 ~ 6.5x10^-4 of an atm. (atm~10^5 N/m^2)

What is acoustic pressure. This question is easy I am sure, but I dont really know what it is asking for. I have read and re-read the chapter on sound waves, but I dont see any term defined as acoustic pressure. I am guessing it is the "overpressure", but I dont know of a relationship between overpressure and Intensity.
From the given information, it almost sounds like you are expected to use the speed of sound and the density of air to come up with the relationship between the reference levels of sound intensity and sound pressure. If that is the case, then it will require more than using the accepted levels. If you are allowed to use the accepted reference levels in your problem, then all you need to do is express the quantities relative to those reference levels and equate the two levels as done here

http://physics.mtsu.edu/~wmr/log_3.htm

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nrqed
Homework Helper
Gold Member
silverdiesel said:
The velocity of sound in air of density rho=1.29 kg/m^3 may be taken to be 330m/s. Show that the acoustic pressure for the painfull sound of 10 W/m^2 ~ 6.5x10^-4 of an atm. (atm~10^5 N/m^2)

What is acoustic pressure. This question is easy I am sure, but I dont really know what it is asking for. I have read and re-read the chapter on sound waves, but I dont see any term defined as acoustic pressure. I am guessing it is the "overpressure", but I dont know of a relationship between overpressure and Intensity.
Have you seen this formula:
$$I = { (\Delta P)_{max}^2 \over 2 \rho v}$$ ??

Patrick

No, what is that formula?