I don't believe the roof is any part of the issue. This sounds like a
simple case of inability of the computer speaker system reject nearby RF
signals. The roof may possibly be a contributor to generating harmonics
due to poor bonding of each element but you are not describing anything
that sounds like harmonic generation.

The issue, in my opinion, is the speakers, speaker amplifiers and/or
sound board in the computer cannot reject the presence of nearby RF
signals..

In the USA the Ham is not legally responsible for the deficiencies in
the computer equipment! He has demonstrated that his station does NOT
interfere with his computer. So, the problem has to be in the offending
computer!

The owner of the computer has the responsibility of adding the necessary
suppression devices to eliminate the RFI. This is generally a series
of snap on toroids on the various wires in the computer system. Very
severe RFI cases may require input from the manufacturer to solve the
problem.

The Ham should not become involved with any add-ons, clamp on ferrites,
or modifications to the offending computer because of legal liability
issues.

Diplomacy and Tact are the key issues for the Ham.

Deacon Dave, W1MCE



Jim Leder wrote:
[SNIP]

but the question is: Could the tin roof be a
contributor to his problem? Would a good ground of the tin roof help?

Thanks...