Technical Is there any straight through muffler that is quiet ?

One variable that you haven't mentioned is where on the car the muffler are mounted. If you mount the mufflers close to the engine or under the front toe board, the air velocity is going to be very high and the car is going to be louder. If you mount the mufflers further back, under the rear seat or even behind the axle, it's going to give it a much deeper, quieter note.

I had a 57 Chevy years ago with a 283 and long tubes. I bought a set of Flowmaster 40 series because I was 16 and had no idea what I should and shouldn't buy. The dude that did the exhaust knew what I was looking for, and basically mounted the mufflers right off the collectors, will all open pipe thereafter. That car was louder than hell and crackled and popped like a set of glasspacks. Then later I changed the trans and had to move the exhaust, and the next shop bent new pipes and mounted the mufflers under the back seat... and the car was quiet like a late-model Mustang or Challenger. The only thing that changed was the placement of the muffler in the chassis. Two totally different sounds.

 

wow this has been very good reading for me! Thank you all Mark

 

I used the mid-length Smithy's with 2" pipes on my '29 roadster, cast-iron manifolds, and was very pleased with the low, mellow, quiet tones it produced. I don't much care for loud any more but I do appreciate a mellow traditional sound of dual exhausts. The mufflers were located well ahead of the rear axle with the pipes running below the axle and out the back. I used 2 1/4" chrome tips which did add to the mellowness of the tone. Exhaust is very subjective, hope this helps.

 

Feel like I should weigh in on this one! I've had my 32 vicky for close to 35 years. Not exaggerating when I tell you I've had 16 (that I can remember) sets of mufflers on it. To me, the tone of the sound is at least as important as the loudness/quietness, and it's totally subjective! Everything matters - - - size of pipe, muffler placement, exit location, and most important ENGINE, specifically cam overlap. What makes your car sound great to me makes mine sound like open exhaust or vice versa. Every one is different. Far as I know all you can do is experiment - - wish there was a formula but there isn't.

 

The way a straight through muffler quiets the exhaust sound is by having perforations in the center tube that allow higher frequencies to escape out of the exhaust stream, and then they are trapped in a glass or steel fiber mesh, so just the lower frequencies are passed on and out the end of the exhaust. As others have mentioned, a shorter muffler will attenuate less and a longer muffler will attenuate more, but at the end of the day there is not much going on to reduce exhaust note volume. But they flow very well since they are straight through with nothing in the way to hamper the flow of exhaust gases.

If you put a slight bend in the inner tube it raises the effectiveness. The muffler will still flow very well, it's still a straight thru design, but the bend in the tube causes reduces the volume more. Something like this: https://www.ebay.com/itm/Universal-...707257?hash=item4881958d79:g:hcsAAOSwAS1ddqsi

But that may be too big or "gloppy" for you. What kind of car are these for anyway?

 

You might also want to just try adding a resonator to your existing exhaust system to reduce droning.
https://www.amazon.com/Vibrant-1141.../B000E3VHWI/?tag=td-exhaust-resonators-pcr-20

 

I like driving fast. Loud is a dead giveaway for that. One of the best examples of this was a '57 Chevy pickup I built when I lived in Pasadena. It had a built 350 in it and I cobbled together the exhaust with mandrel bends and a set of Hemi mufflers from Blairs. It was whisper quiet and stealth to the nines. The only sound I want to hear is the engine moaning and the whistle of the wind. And, yes, I'm more adrenalin junky than a connoiseur of blat, rap, boom and the motorboat sound many of us endure with gritted teeth. Loud pipes are not a spectator sport. Unless you un-pipe one for a race, what you gain in personal satisfaction loses us friends who might be more forgiving as the question of allowing our sport to continue winds its way through state legislative reform. And, brothers and sisters I am one of you and have been long enough to know whereof I speak. So all the junk that can be said about my point of view I've already heard. I'm just pointing out the obvious.

 

https://www.dynomax.com/mufflers/ultra-flo-welded-mufflers

I had these on a vehicle and they were quiet until I stood on it.

 

I said 'stealth'. Some noise comes from them, yeah. They are not everyone's cup of tea. But, I used cast iron manifolds as well. I was after less hassle, from leaking gaskets and traffic safety school from the motor patrol officers. I'll be the first to admit you have to give things up to get others. I've had 235 sixes with baffle split exhaust manifolds and straight out the back exhaust; a Triumph Thunderbird Bobber with unbaffled megaphones; but, there was a price to be paid. Hot Rod Magazine at one time did a decibel test and Hemi mufflers were the winner. I was just making a choice based on that and the fact I grew up in Mississippi where bootleggers built cars that had the appearance of grocery-getters in every respect but ran like stink. The subtlety of that mind set is seductive.