# About acoustics physics -- The Wave Equation and diminishing sound intensity

Hello everyone! :-)

$$\frac{\partial^2\psi}{\partial t^2}=c^2 \nabla^2 \psi$$

which describes practically about pressure and propagation speed into space and time. I know also this equation describes practically also the decrement of sound intensity in time from a source to a destination...if we would talk about particle pressure it's decrement of pressure in space by inverse square-law.
So knowing, for spherical waves , the sound intensity in a certain point of time is:

$$I = \frac{W}{4\pi r^2}$$

and supposing to have a sound diffusor with max power output of 150W and knowing human ear voice range audibility is about 40dB-60dB and supposing I want to have I = 50dB at the time entering in my ear so how I can calculate which power output I have to set the sound diffusor to obtain that intensity I I said before?

Could you help me with this little example so I can understand and study all steps to obtain all values in all situations?

Cheers,
Nunzio Luigi

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