In the channel in
which discharge current flows dominate high temperature and high pressure
which contain "conductive plasma ". This condition lasts while
current flows through channel. The current is serried by forces of its
magnetic field on a small cross-section. When current flow is stopped
the pressure of plasma starts breaks free and spreads radially.
Pressure wave moves. Highest pressure is in the area close to the lightning, only few centimeters far from channel of lightning, then getting lower on some distance. Thunder, which is acoustical effect of this pressure, can be heard on some distance of thunder impact like detonation with rumble. If we are far from the impact, we hear some noise. On distance of 10 km we don't hear anything. If we are very close to lightning impact we could lose every feeling about this act. This is happens because of the high pressure which rule in this area.