| More barriers were used to suppress the traffic noise for their availability and construction convenience. However as one obstacle for sound diffraction, a barrier performs much less effectively to block noise with low frequency below about 500Hz. For the deficiency, a new type of barrier called active noise barrier (ANB) would be of great value, which optimally arranged a multi-channel active noise control system to create quiet zones along the barrier top.Aim at engineering application, we set up several active noise barriers in an anechoic chamber with different configurations (coping with system channels per barrier length, barrier's height and arrangement for control units), to analyze and contrast their extra insertion loss (ΔI L) with multiple-frequency components and analog feedback control circuits.In an optimal range below 1/2 wavelength, less separate distance between system channel units largerΔI L ANB would get for multiple-frequency components.Based on 1.22 meter height and 16 channels active control barriers,ΔILof ANB increased on average 0.5dB per 0.4 meter over 100~200Hz 1/3oct frequency band with the barrier height increasing.When the system channel units were arranged in two parallel lines along barrier top (abb. Two line arrangement),ΔILof ANB would be larger for 0.5-3dB over 100-160Hz 1/3oct frequency band contrasting to that of ANB with system channel units arranged in one line (abb. One line arrangement) with the same interval along the barrier. When these two arrangements were set with the same number of system channel units, system with one line arrangement had greaterΔILthan the one with two line arrangement for 1.0dB on average over 100-160Hz 1/3oct frequency band.
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