Nice sensation in my back, occurs from brain activity.

Hi, whenever I hear a soothing voice, after about 5 seconds of hearing it, the upper area of my back tingles nicely, it's a good sensation nothing bad about it, it doesn't make me twitch of shiver.

It also happens when it seems like someone is concentrating on something, in particular showing me a magic trick for example, whether they are concentrating or not.

I'm 14 years old, almost 15, I don't have any physical major physical issues, just the occasional sore neck or back from sitting at the computer, and tiny hunch as well.

Can someone please shed some light on what this is, what it is called, how & why it happens, and other information would be great.

ThankyouP.S: I'm not sure if this is in the right place, I couldn't decide whether to put this in bone and muscle issues or here, but I thought this probably had something more to do with nerves than anything else.