Impact of Perforated Sheet Geometry on the Insertion Loss of Absorptive Silencers

Downloads

Authors

  • Kamil Wójciak Institute of Power Engineering - National Research Institute, Poland ORCID ID 0000-0002-3672-1788
  • Joanna Maria Kopania Institute of Power Engineering - National Research Institute, Poland ORCID ID 0000-0001-9162-6479
  • Patryk Gaj Institute of Power Engineering - National Research Institute, Poland ORCID ID 0000-0001-6436-3466

Abstract

This study evaluates the influence of perforated sheet geometry on the acoustic and aerodynamic performance of absorptive silencers. A modular silencer is developed, enabling the installation of six different perforated metal sheets with varying hole shapes (round, square, elongated), sizes (2 mm to 20 mm), and open area ratios (22 % to 45 %). Glass wool is used as the sound-absorbing filling. Insertion loss, self-noise, and pressure drop are measured in a large reverberation chamber, within the frequency range from 50 Hz to 10 000 Hz, for airflow velocities of 4 m/s, 6 m/s, and 8 m/s. The results indicate that all configurations provide comparable attenuation at low frequencies. Silencers with small round perforations (diameter 2 mm to 6 mm) ensure higher insertion loss and lower self-noise in the mid-frequency range of 1000 Hz to 5000 Hz, without any measurable increase in pressure drop compared to variants with larger or elongated holes. For frequencies above 6300 Hz, perforated sheets with larger holes perform better. Pressure loss differences between all configurations do not exceed 1 Pa at a given flow velocity. The results confirm that aperture size is the primary parameter affecting silencer acoustic effectiveness, while aperture shape and perforation ratio are secondary. These findings provide practical guidelines for optimal silencer design in ventilation systems, ensuring maximum noise reduction with minimal airflow resistance.

Keywords:

silencers, insertion loss, experimental test, aeroacoustics, ventilation

References


  1. Abramkina D. (2023), Noise from mechanical ventilation systems in residential buildings, E3S Web of Conferences, 457: 02007, https://doi.org/10.1051/e3sconf/202345702007

  2. Allam S., Lbom M. (2011), A new type of muffler based on microperforated tubes, Journal of Vibration and Acoustics, 133(3): 031005, https://doi.org/10.1115/1.4002956

  3. Asdrubali F., Pispola G. (2007), Properties of transparent sound-absorbing panels for use in noise barriers, The Journal of the Acoustical Society of America, 121(1): 214–221, https://doi.org/10.1121/1.2395916

  4. Gaj P., Kopania J., Wojciak K., Bogusławski G. (2019), Assessment of sound absorbing properties of composite made of recycling materials, Vibrations in Physical Systems, 30(1): 2019109.

  5. Harvie-Clark J., Conlan N., Wei W., Siddall M. (2019), How loud is too loud? noise from domestic mechanical ventilation systems, International Journal of Ventilation, 18(4): 303–312, https://doi.org/10.1080/14733315.2019.1615217

  6. Hoshi K. et al. (2020), Implementation experiment of a honeycomb-backed MPP sound absorber in a meeting room, Applied Acoustics, 157: 107000, https://doi.org/10.1016/j.apacoust.2019.107000

  7. International Organization for Standardization (1984), Air distribution and air diffusion – Rules to methods of measuring air flow rate in an air handling duct (ISO Standard No. 5221:1984), https://www.iso.org/standard/11223.html

  8. International Organization for Standardization (2003), Acoustics – Laboratory measurement procedures for ducted silencers and air-terminal units – Insertion loss, flow noise and total pressure loss (ISO Standard No. 7235:2003), https://www.iso.org/standard/30385.html

  9. International Organization for Standardization (2010), Acoustics – Determination of sound power levels and sound energy levels of noise sources using sound pressure – Precision methods for reverberation test rooms (ISO Standard No. 3741:2010), https://www.iso.org/standard/52053.html

  10. Kang J., Brocklesby M.W. (2005), Feasibility of applying micro-perforated absorbers in acoustic window systems, Applied Acoustics, 66(6): 669–689, https://doi.org/10.1016/j.apacoust.2004.06.011

  11. Lan L., Sun Y., Wyon D.P., Wargocki P. (2021), Pilot study of the effects of ventilation and ventilation noise on sleep quality in the young and elderly, Indoor Air, 31(6): 2226–2238, https://doi.org/10.1111/ina.12861

  12. Maa D.-Y. (1998), Potential of microperforated panel absorber, The Journal of the Acoustical Society of America, 104(5): 2861–2866, https://doi.org/10.1121/1.423870

  13. Montgomery D.C., Runger G.C. (2018), Applied Statistics and Probability for Engineers, Wiley, Hoboken.

  14. Wu M.Q. (1997), Micro-perforated panels for duct silencing, Noise Control Engineering Journal, 45(2): 69–77, https://doi.org/10.3397/1.2828428

  15. Wojciak K., Kopania J.M., Gaj P. (2025), Acoustic properties of the absorption silencers with a micro-perforated channel in the air-flow, Vibrations in Physical Systems, 36(1): 2025112, https://doi.org/10.21008/j.0860-6897.2025.1.12

  16. Yang C., Cheng L. (2016), Sound absorption of microperforated panels inside compact acoustic enclosures, Journal of Sound and Vibration, 360: 140–155, https://doi.org/10.1016/j.jsv.2015.09.024

  17. Yang C., Cheng L., Hu Z. (2015), Reducing interior noise in a cylinder using micro-perforated panels, Applied Acoustics, 95: 50–56, https://doi.org/10.1016/j.apacoust.2015.02.003

  18. Yu X., Cui F.S., Cheng L. (2016), On the acoustic analysis and optimization of ducted ventilation systems using a sub-structuring approach, The Journal of the Acoustical Society of America, 139(1): 279–289, https://doi.org/10.1121/1.4939785

  19. Zhang X., Yang C., Cheng L., Zhang P. (2020), An experimental investigation on the acoustic properties of microperforated panels in a grazing flow, Applied Acoustics, 159: 107119, https://doi.org/10.1016/j.apacoust.2019.107119