Thanks a lot Mbrit.
That PDF was really awesome. It explained very clearly how to decide various parameters.
But still, it is not clear that whether we have to go for higher TI or lower TI. Since TI increases with smaller attenuation of sound and effective muffler is which has higher attenuation. this clears that we should go for smaller TI, and in the literature in PDF it is mentioned, many times, to go with higher TI.
what do you say in this case?
Do you have any idea, generally, in what range of frequency, sound is produced in the cars we fabricate.