Nasir, M, Hannyka Febriano, and Balisranislam Balisranislam. 2021. “Effect of the Using of Racing Exhaust With Variation Soundproofing Material Against Exhaust Emissions and Noise on 4 Stroke Motorcycle”. MOTIVECTION : Journal of Mechanical, Electrical and Industrial Engineering 3 (3), 135-42. https://doi.org/10.46574/motivection.v3i3.95.