  We report the measurement of the current noise of a tunnel junction driven
out-of-equilibrium by a temperature and/or voltage difference, i.e. the charge
noise of heat and/or electrical current. This is achieved by a careful control
of electron temperature below 1 K at the nanoscale, and a sensitive measurement
of noise with wide bandwidth, from 0.1 to 1 GHz. An excellent agreement between
experiment and theory with no fitting parameter is obtained. In particular, we
find that the current noise of the junction of resistance R when one electrode
is at temperature T and the other one at zero temperature is given by S = 2 ln2
kB T /R.
