In the diploma thesis I describe the loudspeaker cone as a dumped forced oscilator and present an experiment in which the natural frequency of the loudspeaker system is measured. I show, that the resonant frequency changes if loudspeaker operates in helium atmosphere or vacuum, because of the air or helium load mass. I measure and estimate the mass of the load air and helium. The cone is also represented as a piston, which causes a pressure difference. I attach loudspeaker to a panel and show that this way the loudspeaker efficiency improves.