Development of a Practical Two-Microphone Impedance Tube Method for Sound Transmission Loss Measurement of Sound Isolation Materials

  • Ro, Sing-Nam (Department of Mechanical Engineering, Seoul National University of Technology) ;
  • Hwang, Yoon (Department of Mechanical Engineering, Seoul National University of Technology) ;
  • Lee, Dong-Hoon (Department of Mechanical Engineering, Seoul National University of Technology)
  • Published : 2003.09.01

Abstract

This study developed a practical two-microphone impedance tube method to measure the sound transmission loss of sound isolation materials without the use of an expensive reverberation room or an acoustic intensity probe. In order to evaluate the validation and applicability of the two-microphone impedance tube method, sound transmission losses for several sound isolation materials with different surface density and bending stiffness were measured, and the measured values were compared with the results from the reverberation room method and the theory. From the experimental results, it was found that the accuracy of sound transmission loss obtained by the impedance tube method depends upon the diameter size of the impedance tube (i.e., tested sample size). For sound isolation materials having relatively large bending stiffness such as acryl, wood, and aluminum plates, it was found that the impedance tube method proposed by this study was not valid to measure the sound transmission loss. On the other hand, for sound isolation materials having relatively small bending stiffness such as rubber, polyvinyl, and asphalt sheets, the comparisons of transmission loss between the results from the impedance tube method and the theory showed a good agreement within the range of the frequencies satisfying the normal incidence mass law. Therefore, the two-microphone impedance tube method proposed by this study can be an effective measurement method to evaluate the sound transmission loss for soft sound isolation sheets having relatively small bending stiffness.

Keywords

References

  1. Lee, D. H., Lee, T. K., Cheong, S. K., Lee, H. W., Kang, M. and Kim, Y. B., 2000, Development of sound isolation sheets with compound materials, Autumn Conference Proceedings of the Korean Society for Noiseand Vibration Engineering, Chonan Korea, pp. 415-420
  2. ASTM E90-90, 1990, Standard test method for laboratory measurement of airborne sound transmission loss of building partitions, ASTM, Philadelphia, PA 19103
  3. Crocker, M. J., Raju, P. K. and Forssen, B., 1981, Measurement of transmission loss of panels by the direct determination of transmitted acoustic intensity, Noise Control Engineering Journal, Vol. 17 (1), pp. 6-11
  4. Wang, Y. S. and Crocker, M. J., 1982, Direct measurement of transmission loss of aircraft structures using the acoustic intensity approach, Noise control Engineering Journal, Vol. 19 (3), pp. 80-85
  5. Bolton, J. S., Yun, R. J., Pope, J. and Apfel, D.,1997, Development of a new sound transmission test for automotive sealant materials, SAE transactions, Jr. Pass. Cars., Vol. 106, pp. 2651-2658
  6. Lee, D. H., Kim, D. W. and Seto, K., 2001, A study on measurement of sound transmission loss for sound isolation sheets by two-microphone impedance tube method, Proceedings of the 8th International Congress on Sound and Vibration, 2-6 July, Hong Kong, China, pp. 2423-2430
  7. Lee, D. H., Yong, H. T. and Lee, S., 2002, Sound transmission loss measurement for sound isolation sheets by two-microphone impedance tube method, Korean Journal of Air-Conditioning and Refrigeration Engineering, Vol. 14, No. 1, pp. 63-72
  8. Lee, D. H., Kang, Moon and Seto, K., 2000, A study of validity on the sound transmission loss measurement of sound isolation sheets using two-microphone, Autumn Conference Proceedings of the Korean Society of Automotive Engineering, Vol. 1, pp. 518-523
  9. Lee, S. Y., Kim, J. S. and Kang, Y. J., 1999, Parameter estimation and transmission loss prediction of multi-layered sound absorbing systems by using transfer matrix method, Proceedings of the Korean Society for Noise and Vibration Engineering, pp. 698-702
  10. Seybert, A. F. and Ross, D. F., 1977, Experimental determination of acoustic properties using a two-microphone random excitation technique, J. Acoust. Soc. Am., Vol.61 (5), pp. 1362-1370
  11. Seybert, A. F., 1988, Two-sensor methods for the measurement of sound intensity and acoustic properties in ducts, J. Acoust. Soc.Am., Vol. 83 (6), pp. 2233-2239.
  12. Chung, J. Y. and Blaser, D. A., 1980, Transfer function method of measuring in-duct acoustic properties-I. Theory and II. Experiment, J. Acoust. Soc. Am., Vol. 68 (3), pp. 907-921
  13. Jones, R. E., 1979, Intercomparisons of laboratory determinations of airborne sound transmission Loss, J. Acoust. Soc. Am., Vol. 66 (1), pp.148-164
  14. Harris, C. M., 1996, Shock and Vibration Handbook (4th edition), Chap. 7, McGraw-Hill Book Company