A study on the acoustic performance of array silencer combined with active noise control

Array silencers are widely used in large airflow aerodynamic noise control due to their high flow-through ratio, low airflow resistance, and low regeneration noise. However, the acoustic performance of an array silencer in low frequencies is inadequate. To enhance the low-frequency transmission loss ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>T</mml:mi> <mml:mi>L</mml:mi> </mml:mrow> </mml:math> ), this study combined array silencers with Active Noise Control (ANC) and the acoustic performance of active array silencers was investigated through simulations and experiments, which clarified the enhancement effect of ANC on the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>T</mml:mi> <mml:mi>L</mml:mi> </mml:mrow> </mml:math> of array silencers with different structural parameters (cross-sectional side length ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>a</mml:mi> </mml:mrow> </mml:math> ) of anechoic columns, aspect ratio of anechoic column amount ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>A</mml:mi> <mml:mi>R</mml:mi> </mml:mrow> </mml:math> ), flow-through ratio ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>r</mml:mi> </mml:mrow> </mml:math> )). Results showed that when <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>r</mml:mi> </mml:mrow> </mml:math> =0.56, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>a</mml:mi> </mml:mrow> </mml:math> =150 mm, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>A</mml:mi> <mml:mi>R</mml:mi> </mml:mrow> </mml:math> =1:4 and ANC was on, the increment of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>T</mml:mi> <mml:mi>L</mml:mi> </mml:mrow> </mml:math> was less than or equal to 0 dB at each 1/1 octave band with a center frequency greater than 1000 Hz. When there was no airflow, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>T</mml:mi> <mml:mi>L</mml:mi> </mml:mrow> </mml:math> increased by 200.0%, 148.4%, 55.4%, and 23.1%, respectively at each 1/1 octave band with a center frequency of 63 Hz-500 Hz. When airflow was present in the same direction as sound propagation, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>T</mml:mi> <mml:mi>L</mml:mi> </mml:mrow> </mml:math> increased by 14.3%, 88.3%, 25.3%, and 5.4%, respectively. When airflow was present in the direction opposite to sound propagation, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi>T</mml:mi> <mml:mi>L</mml:mi> </mml:mrow> </mml:math> increased by 18.2%, 37.5%, 5.6%, and -15.2%, respectively. The active array silencer can be widely applied in situations with large airflow and high requirements for low-frequency noise reduction performance.