Difference potential based active noise shielding in three dimensional settings

Active noise shielding based on the Difference Potential Method has been developed and validated in previous publications. The key ability of the method, to provide global noise cancellation while automatically preserving wanted sound in multi-connected domains, has been demonstrated clearly in 1D experiments. In this paper, the tests are extended to 3D. The shielded domain is a 1mx1mx1m box with 1-3 sides open. Up to 4 control sources were used on each of the open sides to shield the domain from external noise. Noise attenuation of around 10dB was achieved up to about 350 Hz. The attenuation is lower than the >20dB attenuation achieved in previous 1D experiments. A reason for this is the sensitivity of the cancellation to the positioning of sensors and controls and the physical size of the control sources. Furthermore, up till now the method relies on separate measurements of the total sound field without the control sources. In realistic applications where noise and wanted sound are non-stationary, the total sound field has to be measured in real time with the control sources operating. In such cases a new mathematical formulation is needed, and this paper will discuss how such a solution can be achieved.