Prediction of noise from mechanical ventilation systems in dwellings: case studies

Noise caused by mechanical ventilation systems in dwellings remains a common problem in practice. To help designers and installers, a simplified acoustic calculation tool has been developed which can be used without detailed acoustic knowledge. The tool is based on the prediction models in EN 12354-5 and VDI 2081 and takes into account the airborne duct sound. The model has been validated by multiple case studies in dwellings. For each case study, the noise levels and airflow rates of the mechanical ventilation system have been measured in each room. Generally, the global A-weighted noise level is predicted with an accuracy of ± 3 dB, on the condition that the airborne duct sound is dominant and sufficiently accurate acoustical input data are available for key components like fans, silencers and air openings. However, some measurement results cannot be predicted by the simplified calculation framework, e.g. when turbulence in two closely placed fittings leads to additional flow noise. The uncertainty also increases when the fan sound is dominated by tonal components.