As I walked into a convenience store I heard this noise go off. I noticed every time someone walked in or out the same noise would sound. I was very intrigued by this; I had never seen anything like it before. It made me think I needed one for my house for when my two year old tried to escape. I really looked into it when I got home and they had all kinds of door chime to choose from. Looks like I have some decisions to make.