Primarily, Acoustic performance of muffler are evaluated by
insertion loss (IL) and backpressure/restriction. Where Insertion
loss is mainly depends upon proper selection of muffler volume,
which is proportional to Engine Swept volume, along with internal
design configuration, which drives the acoustic principle. Same
time, meeting the vehicle level pass by noise (PBN) value as per
regulatory norms and system level backpressure as per engine
specification sheet are the key evaluating criteria of any good
exhaust system. Here, a new Reactive/Reflective type muffler of
tiny size have designed for heavy commercial vehicle application,
which is unique in shape and innovative to meet desire performance.
In this design, mainly sudden expansion, sudden contraction, flow
through perforation and bell-mouth flow phenomenon are used. The
performance of this tiny muffler are optimized using multilevel
design of experiments (DoE) by the measurement of pass by noise
(PBN) and near exhaust noise (NEN) level and Backpressure of
exhaust system along with predictive design calculation. The
primary objective of this research is to investigate the effect of
four design factors namely perforation percentage, perforation hole
diameter, baffle thickness and baffle position on both acoustic
performance and backpressure. The other objective is to do the
comparative assessment between tiny size reactive muffler and
existing 3-chamber hybrid or combination type muffler in holistic
approach on typical heavy commercial truck. This comprehensive
study reveals the importance of perforation baffle feature
(preformation percentage, Perforation-hole diameter, baffle
thickness) and baffler positioning in two chamber muffler to
tradeoff between Noise (PBN & NEN) and Backpressure. Even
though, the new muffler is meeting the regulatory norms but
acoustic performance is marginally inferior to available hybrid
type muffler. The predictive insertion loss value found matching
with 98% accuracy. Further, the new muffler found very much cost
effective, lighter weight and ease package-able/manufacture-able
than existing one. Keywords: Tiny muffler, Backpressure, Pass by
Noise, Near Exhaust Noise