The audio quality is excellent, thanks to VTech's use of DECT 6.0, so you shouldn't hear any interference, static, or echoing when you listen in on your baby. Since the monitor uses a special frequency to relay the signal from the monitor in your baby's room to the parental unit, everything is encrypted and secure. No one but you will hear your baby.
The battery life even when it was "working" is terrible. The screen would glitch out all the time. Now, 10 months in, the last 2 months the power port is broken as a million other reviews have stated. We tried to work around it and have to get the cord "just right" and pulled at an angle, and put something heavy on the cord in order to get it to charge. Now that hardly works. Also, when the blue light is on that it's "charging," half the time it's not even charging any longer, and holds zero charge. I've had the monitor die on me multiple times in the middle of the night recently as it continues to deteriorate. I've been sleeping terrible (my kid is not a good sleeper, still has acid reflux) waking in a panic to look at monitor only to find yes, it is indeed dead.
Wireless encryption: This ensures that no one else can tap into your monitor’s “feed” and see what’s going on in your house. WiFi-enabled monitors are great for portability and range, but may be more susceptible to hacking. If you go this route, be sure to secure your home wireless network and keep the monitor’s firmware updated. Otherwise look for digital monitors with a 2.4 GHz FHSS wireless transmission.