This is a real problem. A caller calls the S9 owner (my spouse). The S9 owner hears the caller perfectly with great Samsung quality. The caller, however, is in a noisy environment with background noise. The S9 "hears" the background noise and seems to think it is about to echo. It seems to echo suppress based on the noise coming in. The S9 attenuates the outgoing sound, apparently in both volume and frequency range, to the point where the caller can no longer hear the S9 owner. It literally sounds like the phone was put under a pillow. Muffled and Muted are both describing the effect.
BTW- The case is an Otter Box and it does not make any difference if the phone is in the case or not.
If the S9 owner turns off speaker phone mode, the sound is crystal clear. If the S9 owner turns off HD Calling, the speakerphone mode works better but still gets muffled if there is a noisy room or car on the caller's side.
Samsung (or Verizon?) needs to address the outgoing muting on the S9. My spouse says that my S7 does not muffle when I am on speakerphone and they are in a noisy area.
Come on. SOMEBODY must be working a fix for this after a year now!