Compressor housing add-on

The housing (40) has a central opening (42) for guiding gaseous medium flowing against channel of a compressor of an exhaust-gas turbo charger, and an annular hollow cavity (43) surrounding the opening. An external supply pipe supplies gaseous medium into the hollow cavity, and a discharge pipe discharges the medium from the hollow cavity. The discharge pipe is axially aligned and arranged on the auxiliary housing side fastened to a muffler. A disk-shaped cover plate (45) is arranged in the hollow cavity between the supply pipe and the discharge pipe. An independent claim is also included for a muffler connected to a compressor housing of an exhaust-gas turbocharger.