Considering the green transformation, more and more attention must be paid to reducing noise pollution, which is one of the most important environmental problems today. Internal combustion engine (ICE) powered hand tools and small appliances, such as leaf blowers, brush cutters, chainsaws, and lawn mowers, are examples of the most undesirable sources of noise in today’s human environment. This paper discusses the acoustic properties of a novel and compact silencer for a small twostroke ICE and proposes a novel concept with corresponding acoustic properties. The proposed solution has been measured on a test bench, and its properties, including transmission loss (TL) and reflection and absorption properties, have been experimentally determined. Using 3D printing technology and technological advantages, an innovative silencer with up to two microperforated (MP) panels, integrated into the expansion chamber of the original silencer, has been applied for rapid prototyping. As a result, noise reduction has been increased by at least 20 dB in the frequency range 800–4000 Hz.
1. Kabral, R., Rämmal, H. and Lavrentjev, J. Acoustic studies of micro-perforates for small engine silencers. SAE Tech. Pap. 2012-32-0107, 2012.
https://doi.org/10.4271/2012-32-0107
2. Kabral, R., Rämmal, H., Lavrentjev, J. and Auriemma, F. Acoustic studies on small engine silencer elements. SAE Tech. Pap. 2011-32-0514, 2011.
https://doi.org/10.4271/2011-32-0514
3. Rämmal, H., Åbom, M., Tiikoja, H. and Bodén, H. Experimental facility for the complete determination of sound transmission in turbochargers. SAE Tech. Pap. 2010-01-1424, 2010.
https://doi.org/10.4271/2010-01-1424
4. Maa, D.-Y. Theory and design of microperforated panel sound-absorbing constructions. Sci. Sin., 1975, 18(1), 55–71.
5. Maa, D.-Y. Microperforated-panel wideband absorbers. Noise Control Eng. J., 1987, 29(3), 77–84.
https://doi.org/10.3397/1.2827694
6. Maa, D.-Y. Potential of microperforated panel absorber. J. Acoust. Soc. Am., 1998, 104(5), 2861–2866.
https://doi.org/10.1121/1.423870
7. Auriemma, F., Rämmal, H. and Lavrentjev, J. Micro-grooved elements – a novel solution for noise control. SAE Int. J. Mater. Manuf., 2013, 6(3), 599–610.
https://doi.org/10.4271/2013-01-1941
8. Villau, M., Rämmal, H. and Lavrentjev, J. Acoustic study of multi-layered microperforated elements for fibreless noise control applications. IOP Conf. Ser.: Mater. Sci. Eng., 2021, 1140, 012015.
https://doi.org/10.1088/1757-899X/1140/1/012015
9. Villau, M., Rämmal, H. and Lavrentjev, J. Concept study of sustainable noise control solution for HVAC systems based on microperforated elements. Proc. Estonian Acad. Sci., 2021, 70(4), 461−469.
https://doi.org/10.3176/proc.2021.4.13
10. Rämmal, H. and Lavrentjev, J. Endurance of micro-perforated elements in unmanned ground vehicle’s small diesel engine silencer application. SAE Tech. Pap. 2019-32-9533, 2020.
https://doi.org/10.4271/2019-32-0533
11. Rämmal, H. and Lavrentjev, J. Reliability study of micro-perforated elements in small engine silencer application. SAE Tech. Pap. 2017-32-0075, 2017.
https://doi.org/10.4271/2017-32-0075
12. Sontech. https://www.sontech.se/product-page/acustimet (accessed 2022-10-25).
13. ISO 10534-2:1998. Acoustics – Determination of sound absorption coefficient and impedance in impedance ducts – Part 2: Transfer-function method.
14. Lavrentjev, J. and Rämmal, H. Experimental study of noise barrier boards with increased acoustic performance by utilizing Helmholtz resonator effects. Mater. Today, 2020, 28(4), 2566–2571.
https://doi.org/10.1016/j.matpr.2020.05.402
15. Lavrentjev, J. and Rämmal, H. On experimental techniques to determine acoustic performance of small exhaust silencers. SAE Tech. Pap. 2009-32-0015, 2009.
16. Lavrentjev, J. and Rämmal, H. Design and performance of acoustic metamaterial structure for inlet duct noise attenuation. SAE Tech. Pap. 2017-32-0066, 2017.
https://doi.org/10.4271/2017-32-0066
17. Åbom, M. Measurement of the scattering-matrix of acoustical two-ports. Mech. Syst. Signal Process., 1991 5(2), 89–104.
https://doi.org/10.1016/0888-3270(91)90017-Y
