SURFACE IMPEDANCE CONTROL FOR SOUND ABSORPTION: DIRECT AND HYBRID PASSIVE/ACTIVE STRATEGIES

1997 ◽  
Vol 203 (2) ◽  
pp. 219-236 ◽  
Author(s):  
M. Furstoss ◽  
D. Thenail ◽  
M.A. Galland
Keyword(s):  
Surface Impedance ◽  
Sound Absorption ◽  
Impedance Control

scholarly journals Study on the sound absorption behavior of multi-component polyester nonwovens: experimental and numerical methods

2018 ◽  
Vol 89 (16) ◽  
pp. 3342-3361 ◽  
Author(s):  
Tao Yang ◽  
Ferina Saati ◽  
Kirill V Horoshenkov ◽  
Xiaoman Xiong ◽  
Kai Yang ◽  
...  
Keyword(s):  
Numerical Methods ◽  
Absorption Coefficient ◽  
Empirical Model ◽  
Surface Impedance ◽  
Sound Absorption ◽  
Low Frequency ◽  
Accurate Method ◽  
Small Error ◽  
Sound Absorption Coefficient ◽  
Acoustical Properties

This study presents an investigation of the acoustical properties of multi-component polyester nonwovens with experimental and numerical methods. Fifteen types of nonwoven samples made with staple, hollow and bi-component polyester fibers were chosen to carry out this study. The AFD300 AcoustiFlow device was employed to measure airflow resistivity. Several models were grouped in theoretical and empirical model categories and used to predict the airflow resistivity. A simple empirical model based on fiber diameter and fabric bulk density was obtained through the power-fitting method. The difference between measured and predicted airflow resistivity was analyzed. The surface impedance and sound absorption coefficient were determined by using a 45 mm Materiacustica impedance tube. Some widely used impedance models were used to predict the acoustical properties. A comparison between measured and predicted values was carried out to determine the most accurate model for multi-component polyester nonwovens. The results show that one of the Tarnow model provides the closest prediction to the measured value, with an error of 12%. The proposed power-fitted empirical model exhibits a very small error of 6.8%. It is shown that the Delany–Bazley and Miki models can accurately predict surface impedance of multi-component polyester nonwovens, but the Komatsu model is less accurate, especially at the low-frequency range. The results indicate that the Miki model is the most accurate method to predict the sound absorption coefficient, with a mean error of 8.39%.

Sensor—actuator tile for underwater surface impedance control studies

1997 ◽  
Vol 102 (3) ◽  
pp. 1573-1581 ◽  
Author(s):  
Robert D. Corsaro ◽  
Brian Houston ◽  
Joseph A. Bucaro
Keyword(s):  
Surface Impedance ◽  
Impedance Control ◽  
Sensor Actuator

scholarly journals Error Sensing Strategy for Active Control of Low-Frequency Sound Absorption of Micro-Perforated Panel Absorber by Using a Point Force Controlled Thin Plate

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Xiyue Ma ◽  
Kean Chen ◽  
Lei Wang ◽  
Yang Liu
Keyword(s):  
Absorption Coefficient ◽  
Active Control ◽  
Surface Impedance ◽  
Sound Absorption ◽  
Low Frequency ◽  
Point Force ◽  
Sound Absorption Coefficient ◽  
Error Signal ◽  
Frequency Sound ◽  
Highly Correlated

This paper presents an analytical investigation on constructing an error sensing strategy of a new type of active MPPA. The proposed active MPPA is composed of MPP, air cavity, and point force-controlled backing panel, which can actively improve the low-frequency sound absorption of the MPPA. Constructing an appropriate error sensing strategy for obtaining an error signal that is highly correlated with the sound absorption coefficient of the active MPPA is a key problem encountered in practical implementation. The theoretical model of the active MPPA is firstly established using the modal analysis approach. Then, the active control performance and surface impedance characteristics in the controlled condition are analyzed in detail. Finally, the error sensing strategy of the active MPPA is constructed by measuring the surface average impedance ratio with an acoustic vector sensor (AVS). Simulation results show that, due to the antisymmetric property of the vibration of the backing panel on the resonant frequency, the surface impedance of the active MPPA after control also has symmetry or antisymmetry properties. Hence, the surface average impedance ratio of the active MPPA can be measured by using the limited number of acoustic vector sensors (sensing pressure and particle velocity). This variable is also highly correlated with the sound absorption coefficient of the active MPPA and thus can be used to construct the cost function (error signal). The active control result obtained by the proposed error sensing strategy is in good agreement with the theoretically optimal result, which validates the feasibility of this approach.

PONDEROMOTIVE EFFECT OF ELECTROMAGNETIC WAVES ON THIN VIBRATORS WITH WEAKLY PERTURBED SURFACE IMPEDANCE

2020 ◽  
Vol 79 (14) ◽  
pp. 1205-1215
Author(s):  
Yu. M. Penkin ◽  
V. A. Katrich ◽  
M. V. Nesterenko ◽  
S. L. Berdnik
Keyword(s):  
Surface Impedance ◽  
Electromagnetic Waves
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