  We use a combination of analytical theory, numerical simulation, and data
analysis to study the propagation of acoustic waves along coronal loops. We
show that the intensity perturbation of a wave depends on a number of factors,
including dissipation of the wave energy, pressure and temperature gradients in
the loop atmosphere, work action between the wave and a flow, and the
sensitivity properties of the observing instrument. In particular, the scale
length of the intensity perturbation varies directly with the dissipation scale
length (i.e., damping length) and the scale lengths of pressure, temperature,
and velocity. We simulate wave propagation in three different equilibrium loop
models and find that dissipation and pressure and temperature stratification
are the most important effects in the low corona where the waves are most
easily detected. Velocity effects are small, and cross-sectional area
variations play no direct role for lines-of-sight that are normal to the loop
axis. The intensity perturbation scale lengths in our simulations agree very
well with the scale lengths we measure in a sample of loops observed by TRACE.
The median observed value is 4.35x10^9 cm. In some cases the intensity
perturbation increases with height, which is likely an indication of a
temperature inversion in the loop (i.e., temperature that decreases with
height). Our most important conclusion is that thermal conduction, the primary
damping mechanism, is accurately described by classical transport theory. There
is no need to invoke anomalous processes to explain the observations.
