My refrigerator makes some short anomalies in electric network in my apartment whenever it starts/stops its compressor. I'm not sure if it's a brief frequency change or voltage drop. I can notice this by hearing loud bang in my guitar amp (when it's turned on). Also I can hear it in my headphones when they're connected to my PC - both desktop and laptop when it's plugged in.
How can I protect my equipment from that? I have tried line-interactive UPS with AVR (APC BX950U-GR), but situation stayed the same. I cannot afford an online UPS.
What kind of equipment can solve my problem? If that's an AVR, what specification it should have?