Sarah - we have an angel care monitor too and it buzzez when I have it out in the garage with the computer and mobile phone close by. It's not so bad inside. Gabby has music or a fan going in her room all the time when she is sleeping so I am used to some kind of noise coming out of it. I don't use it at night either because I can hear her with both doors closed n e way.
So... in other words... I am absolutely no help to you!! LOL