Does the volume of music affect the concentration for people?

Normally, Yes.

Can you explain why it affects the concentraion for people?

Loud music is distracting and it hurts the ears.

The type of music makes a difference too. That's why "elevator music" is used as telephone waiting music while a caller is on hold, music faintly heard in stores, etc. a bland easy-listening music ("white noise") that covers the silence but doesn't intrude on conversation and shoppers' thoughts.