Real time reduction of HVAC noise using a FPGA

An important application of Active Noise Control (ANC) is to reduce noise produced by machinery in modern living places. We present an ANC system that is designed to cancel narrowband noise generated from the compressor of an HVAC (Heating, Ventilation, and Air-Conditioning) system in real time. To achieve cost effectiveness of the system, we propose a single-channel Feedback ANC implementation, which uses only a single speaker and a single microphone. The ANC algorithm is implemented on a NI 7833R Reconfigurable I/O (RIO) FPGA board. A leakage factor is required to ensure stability of the system because of the inherent quantization error in fixed-point implementation of ANC algorithms. To alleviate the effect of quantization error, the fixed-point length is increased from 24 bits to 32 bits, to improve the performance. By correctly choosing the leakage factor, the Leaky Feedback ANC implementation allows for stable reduction of the HVAC compressor noise ranging from 4.59 to 10.73 decibels (dB).