StVO § 1 Abs. 2:
"(...) (2) Every road user shall behave in such a way that no one else is harmed, endangered or more than is unavoidably, hindered or harassed by the circumstances."
StVO § 23 para. 1:
"(...) (1) The driver is responsible for ensuring that his vision and hearing are not affected by the occupancy, animals, cargo, equipment or condition of the vehicle. (...)"
Zu Fahrfehlern durch Ablenkung
Very loud music disturbs the concentration and thus the attentive, anticipatory driving. It distracts and can lead to driving errors.