Development of Instrumentation for the Measurement of the Performance of Acoustic Absorbers

Maria A.  Kuczmarski; James Christopher  Johnston; Garth  Olszko

doi:10.4236/oja.2015.54014

James Christopher Johnston¹, Maria A. Kuczmarski¹, Garth Olszko²

Abstract: In both fixed and rotary wing aircraft, the move toward lighter structures has resulted in an increase in structural vibration and interior noise. Porous materials have been proposed as acoustic absorbers to reduce this noise. This paper discusses the development of equipment at the NASA Glenn Research Center for characterizing the acoustic performance of porous materials: a flow resistance apparatus to measure the pressure drop across a specimen of porous material, and a standing wave tube that uses a pair of stationary microphones to measure the normal incidence acoustic impedance of a porous material specimen. Specific attention is paid to making this equipment as flexible as possible in terms of specimen sizes need for testing to accommodate the small or irregular sizes often produced during the development phase of a new material. In addition, due to the unknown performance of newly developed material, safety features are included on the flow resistance apparatus to contain test specimens that shed particles or catastrophically fail during testing. Results of measurements on aircraft fiberglass are presented to verify the correct performance of the equipment.

Keywords: Acoustic Impedance, Acoustic Measurement, Acoustic Attenuation

Cite this paper: Johnston, J. , Kuczmarski, M. and Olszko, G. (2015) Development of Instrumentation for the Measurement of the Performance of Acoustic Absorbers. Open Journal of Acoustics, 5, 172-192. doi: 10.4236/oja.2015.54014.

References

[1] Sampath, A. and Balachandran, B. (1997) Studies on Performance Functions for Interior Noise Control. Smart Materials and Structures, 6, 315-332.
http://dx.doi.org/10.1088/0964-1726/6/3/009

[2] Smith, S.W. (1997) The Scientist and Engineer’s Guide to Digital Signal Processing. California Technical Publishing, San Diego.

[3] Strobel, J., Wigley, E. and Evans, N. (2009) BUZZ-Acoustical Engineering Methodologies to Measure Student Engagement. Research in Engineering Education Symposium, Palm Cove, 1-6.

[4] (2003) ASTM Standard C522-03: Standard Test Method for Airflow Resistance of Acoustical Materials.

[5] Lanoye, R., Bree, H.-E.D., Lauriks, W. and Vermeir, G. (2004) A Practical Device to Determine the Reflection Coefficient of Acoustic Materials in-Situ Based on a Microflown and Microphone Method. International Conference on Noise and Vibration Engineering, Leuven, 11.

[6] (2004) ASTM Standard C384-04 (Reapproved 2011): Standard Test Method for Impedance and Absorption of Acoustical Materials by Impedance Tube Method.

[7] (2012) ASTM Standard E1050-12: Standard Test Method for Impedance and Absorption of Acoustical Materials Using a Tube, Two Microphones, and a Digital Frequency Analysis System.

[8] (2001) BS EN ISO 10534-2: Acoustics—Determination of Sound Absorption Coefficient and Impedance in Impedance Tubes —Part 2: Transfer-Function Method.

[9] Brigham, E.O. (1974) The Fast Fourier Transform. Prentice-Hall, Englewood Cliffs.

[10] Jones, M.G. and Stiede, P.E. (1997) Comparison of Methods for Determining Specific Acoustic Impedance. Journal of the Acoustical Society of America, 101, 2694-2704.
http://dx.doi.org/10.1121/1.418558

[11] Song, B.H. and Bolton, J.S. (2000) A Transfer-Matrix Approach for Estimating the Characteristic Impedance and Wave Numbers of Limp and Rigid Porous Materials. Journal of the Acoustical Society of America, 107, 1131-1152.
http://dx.doi.org/10.1121/1.428404

[12] National Instruments LabVIEW: Austin, TX.