In article 1070919774.530038@smirk, says...
Echo cancelling does nothing to reduce time-of-flight issues.
A half-second delay is still a half-second delay.

A half second is a half second, but canceling the echo does help
intelligibility by removing some noise from the signal. Time-of-flight
isn't the only issue.


Adding reverb is contraindicated for telephone communications,
as it tends to reduce intelligibility. Check out speakerphones
for examples thereof.

Excessive reverb is a bad thing. Done correctly, reverb adds a sense of
presence without interfering with intelligibility.


Signal processing techniques are not useful for fixing problems
due to speed of light causing delays.

True, but these tools are useful for lots of other real-world problems.
--
Kevin Willoughby lid

Imagine that, a FROG ON-OFF switch, hardly the work
for test pilots. -- Mike Collins