Noise reduction efficiency of Helmholtz resonator in simulated channel of HVAC system

 The purpose of this article was investigating the efficiency of designing resonator in decreasing low noises. 

 The designed Helmholtz resonator was installed in a channel analogous to ventilation channel. The resonator was produced signals at very low frequencies (125-500 Hz) and sound pressure levels 60-90 dB and transmitted through a channel by means of a speaker. Afterwards, the variation of sound pressure level was monitored and then intra-channel signals processing and preparing of sound Algorithm in channel was done by MATLAB software. 

 The highest decrease of sound pressure level at 125 Hz frequency among of Helmholtz resonators was observed at chamber diameter of 63 mm and resonator's 1 cm-caliber. Sound pressure level reductions of 0-10 dB were achieved in an experimental duct system using a Helmholtz resonator. 

 This research showed that the designed Helmholtz resonators at a certain frequency of low-frequency sound demonstrated the soundest decrease. The increase in the Helmholtz resonators' chamber volume and their neck's pass area are negatively associated with the rate of sound resonance. As a result, of determining the effective frequency range of the Helmholtz resonator, the designed resonator could be applied as an effective and efficient instrument of removing or decreasing noise.