PorNoise pollution has been given more attention due to its negative impacts on human health and disease.The portable low-frequency
noise reduction device we developed in this research can provide an effective way for solving low-frequency noise pollution problem
in the small space. This work describes the design principle and the prototype structures for two versions of V1.5 and V2.0 and
builds the noise test systems for small spaces, respectively. These devices, installed on the outer surface of the small spaces, can
automatically identify the noise spectrum and implement noise reduction by means of the active noise control (ANC) technology.
The testing results indicate that the noise can be reduced 12 dB in the range of 250 Hz∼400 Hz for the small closed space while, for
the small open space, the best effect of 5.88 dB occurs in the optimal frequency of 450 Hz. These effects will be weakened with the
increasing distance away from the source and show the obvious axisymmetric distribution in the inverted cone space.table Low-Frequency Noise Reduction Device for
Both Small Open and Closed Spaces