A proper training program should be fun for both of you, even (especially?) if extended efforts are needed and results are slow to come.
Surge strips are necessary to protect against high-voltage spikes that might damage something, but can't do much of anything about poor line power quality within the normal tolerances of the service. The power supply in the computer has to live with variations in line voltage that are much wider than most people realize - that the "power guys" consider "normal" - whle still providing stable power to the innards of the computer. A surge suppressor only functions when the voltage goes to "more than normal," and does nothing about variations within the accepted ranges, whether they're variations in voltage at line frequency or rf "signals" imposed on the line.
Speaker noises are unlikely to come from power line deviations of the kind affected by surge suppression, and are much more likely to be related to something going on within the signal level systems within the computer. Some interference can be picked up on power lines, and passed into the computer, but the surge suppressors can't do much of anything about them. Common sources often cited are cell phones, garage door openers, and the neighbors' Wi-Fi. A few instances of interference from weather radar on passing airplanes are reported; but the charges against all of these are somewhat "suspect" when examined closely.
When we first hooked up our new DSL, we had a few days of seemingly random "burps" on the first machine connected that AT&T told Lin were a 'phone line problem that they were "working on" - and they went away a couple of days later. "Advertising" (not quite what I could call "instructions") had mentioned that we should leave the computers on constantly for ('phone) "line quality adjustments" during the first 10 days, and apparently some tweaking was needed. It could be, perhaps, expected that a significant change in a neighbor's service might require "re-tweaks"(?).
Household applicances can cause "audio" noises, especially if they're on the same circuit as the computers. The noise you hear usually is from the "transient" when a switch or relay flips, and not from the voltage sag/recovery produced by running of the appliance.
The speakers quite probably use a separate "power supply" (a wall-wart) plugged into the surge strip. Most of these supply rectified dc voltage, and a deterioration of the "wart" or of the wire to the speakers - or of the connecting wiring between speakers - or an insecure connector plug/socket - could produce erratic noise.
Some ancient solid-state audio circuits, when "turned 'way down," could produce a noise called "popcorn noise" and/or "motorboating" but it's been decades since I've heard (or seen) mention of either term, since the kinds of transistors that produced it simply aren't used in "modern" circuitry (except in diesel-electric locomotives, where "small noises" aren't too much noticed).