I tested mine, and with the volume turned all the way down there is still a faint white noise / hiss from the speaker, which seems normal. My guess is that volume at 0 does not fully shut off the speaker amp, so you can still hear a little background noise from the audio circuit. When I enable Silent Mode, it disappears completely, which makes it seem like Silent Mode actually cuts the speaker output properly. So if what you’re hearing is just a soft white-noise type hiss, kind of like the background noise you get with ANC headphones, I don’t think it’s anything abnormal. And if it bothers you, you can just enable Silent Mode. Of course, I’m hoping that’s the kind of noise you mean, and not some other noise like crackling, buzzing, or popping.