Study of a New Highly Absorptive Acoustic Element

The highly absorptive acoustic element studied in this paper is constituted by two mating plates provided with slots and a number of micro-channels engraved on the contact surface. This fibre-less element has been first presented in a previous work, with the name of micro-grooved element (MGE), as a potential substitute of the well-known micro-perforated element (MPE) (Auriemma et al. in SAE Int J Mater Manuf 6(3), 2013). Compared to MPE, it offered advantages in terms of cost-effectiveness of the production process, but similar acoustic behaviour. In this paper, MGEs with improved design are presented. The new geometry of the outer layers results in inner micro-channels with smaller overall dimensions, while still keeping adequate porosity. As a result, the acoustic behaviour is enhanced and the sound absorption of traditional MPEs is finally overcome. The transfer impedances of several MGE and MPE samples are measured, modelled and compared. The impedance end corrections are extrapolated with a completely experimental procedure and the behaviour in nonlinear regime is studied and described by means of a semi-empirical formulation.

[1]  D Maa,et al.  THEORY AND DESIGN OF MICROPERFORATED PANEL SOUND-ABSORBING CONSTRUCTIONS , 1975 .

[2]  U. Ingard.  On the Theory and Design of Acoustic Resonators , 1953 .

[3]  Li Cheng,et al.  Absorption of oblique incidence sound by a finite micro-perforated panel absorber. , 2013, The Journal of the Acoustical Society of America.

[4]  Walter Eversman,et al.  High Amplitude Acoustic Transmission Through Duct Terminations: Theory , 1983 .

[6]  Allan D. Pierce,et al.  Acoustics , 1989 .

[7]  Sabry Allam.  Numerical Assessment and Shape Optimization of Dissipative Muffler and Its Effect on I.C. Engine Acoustic Performance , 2014 .

[8]  A. Hirschberg,et al.  Non-linear acoustic transfer impedance of micro-perforated plates with circular orifices , 2016 .

[9]  Pedro Cobo,et al.  Microperforated insertion units: An alternative strategy to design microperforated panels , 2006 .

[10]  Masayuki Morimoto,et al.  MULTIPLE-LEAF SOUND ABSORBERS WITH MICROPERFORATED PANELS: AN OVERVIEW , 2010 .

[11]  Mats Åbom,et al.  The influence of edge geometry on end-correction coefficients in micro perforated plates. , 2015, The Journal of the Acoustical Society of America.

[12]  A. Pierce,et al.  Acoustics: An Introduction to Its Physical Principles and Applications. 1989 Edition , 1990 .

[13]  J. Allard.  Propagation of Sound in Porous Media: Modelling Sound Absorbing Materials , 1994 .

[14]  Mats Åbom,et al.  A New Type of Muffler Based on Microperforated Tubes , 2011 .

[15]  D. A. Blaser,et al.  Transfer function method of measuring in-duct acoustic properties. I - Theory. II - Experiment , 1980 .

[16]  Martin Eerme,et al.  DESIGN OF CAR FRONTAL PROTECTION SYSTEM USING NEURAL NETWORK AND GENETIC ALGORITHM , 2012 .

[17]  David W. Herrin,et al.  Enhancing micro-perforated panel attenuation by partitioning the adjoining cavity , 2010 .

[18]  Zheng Zhao,et al.  Investigation on micro-perforated panel absorber with ultra-micro perforations , 2013 .