  We present a calculation of noise in the tunneling current through junctions
between two two-dimensional electron gases (2DEG) in inequivalent Laughlin
fractional quantum Hall (FQH) states, as a function of voltage and temperature.
We discuss the interpretation of measurements of suppressed shot noise levels
of tunneling currents through a quantum point contact (QPC) in terms of
tunneling of fractionally charged states. We show that although this
interpretation is always possible, for junctions between different FQH states
the fractionally charged states involved in the tunneling process are not the
Laughlin quasiparticles of the isolated FQH states that make up the junction,
and should be regarded instead as solitons of the coupled system. The charge of
the soliton is, in units of the electron charge, the harmonic average of the
filling fractions of the individual Laughlin states, which also coincides with
the saturation value of the differential conductance of the QPC. For the
especially interesting case of a QPC between states at filling fractions
$\nu=1$ and $\nu={{1/3}}$, we calculate the noise in the tunneling current
exactly for all voltages and temperatures and investigate the crossovers. These
results can be tested by noise experiments on $(1,{{1/3}})$ QPCs. We present a
generalization of these results for QPC's of arbitrary Laughlin fractions in
their weak and strong coupling regimes. We also introduce generalized Wilson
ratios for the noise in the shot and thermal limits. These ratios are universal
scaling functions of $V/T$ that can be measured experimentally in a general QPC
geometry.
