I appreciate you confirming that information. The $99.99 Video Doorbell is our Classic model which does not feature HD, but instead a 720 resolution. To resolve this audio concern, I recommend performing a reset. Please hold down the orange setup button for 20 seconds. Keep in mind this reset will restore factory settings and will require a new setup to reconnect.
In addition to the reset, try disconnecting the hardwired connection temporarily to see if audio improves without it.