Robin,
If sound and heat are the same phenomenon, then why is the speed
with which heat is conducted through a solid so much lower than
the speed with which sound is propagated?
Why would you assume that it is lower? It isn't always.
And why would you assume that they are the same? Both are lesser
included subsets of "kinetic" wave-forms in matter (phonons), but
are different in the details - while they can appear similar in
those spectrums where there is overlap.
Given that some materials are "sound-proof" but still transfer the
kinetic component of heat - the opposite [for speed of transfer]
is true for them.
"Heat" is normally much higher frequency than sound and applies to
both phonon and photon radiation, yet cannot always be heard
(unless there is a harmonic below about 18 kHz) - but that does
not mean it is always propagated "slower." Sound cannot always be
heard but the frequencies of even ultrasound are much longer than
"heat". ERGO it is "different" in propagation speed, but not
always "slower" due to the fact that heat is broad spectrum, has
BOTH kinetic and photonic waves, while sound is narrower spectrum,
lower frequency, non-photonic, and often much more intense at any
given frequency - and consequently the transfer-medium is more
likely to resonate in bulk at that lower frequency, so the
apparent speed seems higher - since the wavelength is much longer.
Jones
