The exposure to noise from more than one source is no rarity nowadays. In most cases the assessment of immission load is performed for each traffic carrier individually and superposition of different sound levels is not treated in any special way when mitigation measures are realized. Thus, health-impairing situations are not properly resolved or even remain undetected. In order to establish a comprehensive approach for the joint evaluation of road, railway, aircraft and shipping noise immission, we look at different test cases, which serve as exemplary scenarios for critical noise situations. By comparing different calculation and assessment methods (e.g. energetic sum, spectral analysis, weighted noise index, VDI 3722-2 ...) we want to give first answers to the questions: How to calculate the overall sound level when several noise sources are present? How to consider the diverse physiological and psychological effects of noise on people? What are possible unambiguous indicators for triggering acoustically effective mitigation measures?