hum from nearby high-tension wires?

If you can do it, I'd suggest moving. If the overhead power line are affecting your system, imagine what they're doing to your body.

All of the information your body passes, is passed electrically. Strong electrical signals interfere with the transmission of information.

Dr R. C. Brockhaus

Hey, nothing like scaring the guy. Verdict is indeed still out on EM/RF impact on human health. As far as your hi-fi, that is a problem. You can try sheets of ERS cloth and move them around to see if there is a particularly sensitive piece of equipment. could also try humbuster. I assume you have checked to see if it is coming in through your CATV.

These aren't the monster tower kind of transmission lines for long distances, they are local distribution type within city limits that have lower emissions. The only devices affected are sensitive ones like phone preamps and pickups (and, I suppose possibly our nervous systems, although I wonder how EM radiation of this sort could have signifcant coupling with our electrochemical wetware, I seem to remember that our nerves conduct in a different way ("sodium pump"?) than metal wires).

Anyway, thanks for advice, I'll try the radio and fluorescent tube tests. My grandson would be thrilled if we could get the full lightsabre sound and audio effects.

While it is true that the studies are mixed there are studies showing that exposure to electromagnetic fields have adverse effect on cells at the chromosomal level as well as the immune system. There may also be a relationship to certain cancers and neurological diseases.

Another possibility is the university complex itself is the source. There are probably large motors for air condioning and elevators, some of which may be variable frequency drive, that puts noise in the power grid. Another possibility is that the university has a cogeneration plant - generating electricity to the site and selling some power back to the utility. This backfeed will also put noise in the line. In short, that facility may be the culprit and not the substation. Your only solution may be a shielded isolation transformer for the whole house (way too expensive) or for the audio circuits. The xfmr should be grounded at its location.

Also, power quality is an issue that your utility has to address. Whether it's voltage variations (sags and dips) or noise, they are required to have a means of hearing your complaints and to make a good faith attempt to correct these issues. Let them know - maybe they think everyone is happy as they send out their bills.

As a side note, a friend has an office directly across the street from a utility small-scale generating plant. There is no problem with AM or TV reception. The only noticable effect is when you drive only past the front gate and the AM in the car briefly hums out.