DIAGNOSIS
This is not normal operation. The most likely cause is RF interference from a nearby Wi-Fi router or other electronic device disrupting the 5.8GHz wireless signal to the rear speakers.
FIX
1. Power cycle the entire system: unplug the soundbar, subwoofer, and rear speakers from power for 2 minutes.
2. Relocate your Wi-Fi router. Maintain a minimum 3-foot (1-meter) separation between the router and the soundbar or subwoofer.
3. Re-pair the wireless speakers. Press and hold the ID SET button on the back of the subwoofer for 5 seconds.
IF THAT DIDN'T WORK
Check for a defective power supply. Try plugging the rear speaker power adapters into a different, isolated power outlet or surge protector. A shared circuit with other electronics can introduce noise.
HEADS UP
The hiss is not related to volume level. If the noise persists after all steps, contact Samsung support. A consistent hiss across all inputs indicates a potential hardware fault in the transmitter or a speaker.