skin effect: A current-carrying conductor not only builds up a magnetic field around it, but also inside the conductor itself. With an alternating current (like the music signal), its direction is constantly changing – and with it the magnetic field in and around the conductor.
As a result, a reverse voltage is induced in the conductor, which corresponds to the original one Signal opposes and weakens it. This effect occurs in the middle of the line and is frequency-dependent, ie the thickness of the "well-conducting conductor skin" decreases and the "poorly conducting conductor middle" increases with increasing frequency. This "pushing away" of the current to the edge of the conductor, which becomes stronger with increasing frequency, is called the skin effect.