This thesis studies the parameters that affect the sound level of signalhorns in a passenger car. The project is performed on the behalf of VolvoCars Group. Physical testing was done on Volvo S90 with and withoutmodifications. During the project, the influence of installation, frequencysignature of horns and system parameters on sound pressure wereinvestigated. Acoustic measurements were performed in semi anechoicchamber and open site using the setup specified by ECE R28 document.