# Sound radiation from a pulsating sphere

1. May 11, 2012

### mk55

1. The problem statement, all variables and given/known data

Consider a pulsating sphere of radius 0.15m pulsating at a frequency of 2000Hz and surface velocity v$_{}0$=0.07m/s. What is the distance r, where the measured acoustic pressure is 5x10$^{}-2$.
speed of sound c=343m/s
mass density of air ρ$_{}0$=1.25kg/m3

2. Relevant equations
i know im supposed to use these equations:
φ=(A/r)e^(ikr-iωt)
p'=-ρ$_{}0$(dφ/dt)
v=dφ/dr
v=v$_{}0$e^(-iωt)

3. The attempt at a solution
I have differantiated the velocity potential function (φ) and substituted in the formula for p'. i also substituted the value of p' which is 5x10^-2 but after that im stuck because im not sure how to work out t.

Any help would be appreciated
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution