Power and Energy of an Audio file
In principal, you get $\text{Ws}=\text{J}$ for energy and $\text{W}$ for power, but as you are calculating these measures from a wav-file, you do not get any unit. What you get is just a ratio to the maximum possible value of a wav-file. A square wave with amplitude one has a level (power) of $0\text{ dBFs}$, which means dB Fullscale. Your signal has roughly $-75\text{ dBFs}$, so that would be a valid result. If you want to get a result in actual physical units, you will need to know several things:


the sensitivity of the sensor (e.g. a microphone), that was used for audio recording. This is usually given in $\text{dBV/Pa}$
the calibration of the A/D converter used, usually given in form of the overload point in $\text{dBV}$, meaning that a sine wave with this level just drives the ADC to fullscale ($0\text{ dBFs}$), any increasing of the voltage leading to clipping.


With this information, you could calculate back the real power the actual sound event had at the point of the microphone.