Social skills training is a type of psychotherapy that works to help people improve their social skills so they can become socially competent. SST is predominantly a behavioural therapy but cognitive therapy can also be used in some situations to maximise the success of SST.
Often a faulty toilet ballcock (fill valve) will cause resonance sounds like these. At least it's easy to check -- here's how to tell if this is the cause. Close the supply valves to all the toilets. If the noise disappears, open them one-by-one till the noise starts again. Replace the ballcock in that toilet.
SOLAR ENERGY SYSTEMS may include pumps that produce noise in the building - see Pump Noises above. Plumbing vent piping-caused plumbing system noises and odors - At PLUMBING DRAIN VENTS we explain the basics of proper plumbing vent piping and how errors cause trap siphonage, odors, and noises.