Steel Guitar, Pedal Steel Guitar purchasing guide, listen for extraneous noise from the pick-ups. That will bring out hum, buzz, and 'microphonics' if the instrument is prone to unwanted noise. Sometimes, feedback is a desirable sound for rock and heavy metal.
Microphonic noise is never welcome.
The hollow ringing and amplified undercarriage noises caused by microphonic pickups is annoying. Insufficient isolation, as well as improper construction, of the pickups are some of the main causes of these phenomena.