My initial thoughts were to move this to the Mobile audio forum. But I think it's kind of interesting and you've probably got a better shot at a response here. Maybe after the ball gets rolling I'll move it. :T
OT: Automotive exhaust acoustics? Anyone?
Thought I might check to see if anyone here is either up to speed on this or can recommend a forum?
basically I am working on tuning out resonant frequencies in an exhaust system. Trying to learn the typical techniques in mufflers and what is might help me. I am familiar with some baffle designs as well as branch resonators that are designed reflect opposite phase waves at the exhaust stream.
I removed a rotted muffler on our Infiniti FX45 and straight piped from the resonator muffler and it is a touch loud along with some anyone resonances between 100-135hz. I am trying to learn if straight through baffle setups can kill these low frequencies or if reflective chambers are the right way? So many idiots online and I know things get technical quick in room tuning for HT. Seems a great excuse to learn something today...
basically I am working on tuning out resonant frequencies in an exhaust system. Trying to learn the typical techniques in mufflers and what is might help me. I am familiar with some baffle designs as well as branch resonators that are designed reflect opposite phase waves at the exhaust stream.
I removed a rotted muffler on our Infiniti FX45 and straight piped from the resonator muffler and it is a touch loud along with some anyone resonances between 100-135hz. I am trying to learn if straight through baffle setups can kill these low frequencies or if reflective chambers are the right way? So many idiots online and I know things get technical quick in room tuning for HT. Seems a great excuse to learn something today...
1 - 14 of 14 Posts
I'm not familiar with exhaust systems but i was curious if it is the noise entering the interior you are trying to stop? If so it would be extream but you could sound deaden the interior of the car with a Dynamat type material but that is costly and timely, in the long run you would probly be better off just putting back on an OEM exhaust. I'll talk to one of my buddies that knows alot about everything tomorrow and see what he thinks.:TThought I might check to see if anyone here is either up to speed on this or can recommend a forum?
basically I am working on tuning out resonant frequencies in an exhaust system. Trying to learn the typical techniques in mufflers and what is might help me. I am familiar with some baffle designs as well as branch resonators that are designed reflect opposite phase waves at the exhaust stream.
I removed a rotted muffler on our Infiniti FX45 and straight piped from the resonator muffler and it is a touch loud along with some anyone resonances between 100-135hz. I am trying to learn if straight through baffle setups can kill these low frequencies or if reflective chambers are the right way? So many idiots online and I know things get technical quick in room tuning for HT. Seems a great excuse to learn something today...
While my theories on this are to far from proven to give any advise I could back up. What I will say is that Flowmaster has done some great research on back pressure and sonic movement interacting. I don't think they offer detail in the order you would like to read but if you are willing to go with a "it just works" approach then, me personally I would look no further.
Actually the stock car, because it is an Infiniti, has damping materials on most of the metal panels. They are damping systems that act to increase the mass and lower the resonant frequency outside the operating range of the car. As I understand it, the exhaust hits a note of high enough amplitude to excite the body panels and such and you end up with a pretty lively interior.
I was reading something this evening that indicated straight through muffler designs do very little for low/long frequency waves. I can only assume you need to be at least 1/4 of the wave length to do it that way so maybe a 3ft long muffler....
I know these issues are VERY apparent in HT. Reflections from walls causing huge holes in audio response, etc. I guess possibly the resonance in a car cabin would be compared to standing in the corner while hitting a low note with the sub.
I was reading something this evening that indicated straight through muffler designs do very little for low/long frequency waves. I can only assume you need to be at least 1/4 of the wave length to do it that way so maybe a 3ft long muffler....
I know these issues are VERY apparent in HT. Reflections from walls causing huge holes in audio response, etc. I guess possibly the resonance in a car cabin would be compared to standing in the corner while hitting a low note with the sub.
basically the car comes out with a cat on each bank (2), then merges to 1, goes through a resonator muffler, then into a silencer muffler at the very back of the car and comes out of that with 2 pipes to the tips. I deleted the last muffler and ran a single pipe from the resonator, to a Y, then out to each tip. Piping is 4ft to each tip from the resonator.What mufflers did you use to replace the rotten ones? Just to make sure I understand correctly.... Did you bypass the stock resonators with straight pipes?
Back when i was shopping for exaust for my Silverado i was looking at Corsa exaust, from what i remember they had 3 different offerings of exhaust depending how you wanted your vehicle to sound more or less they had small medium and large which means that they had a nice simple quiet one or a loud rumbling one or the middle which had both options that when you take off from a stop or punch the gas it got loud then when you settled back down to cruising speed it just held a nice modest tone. As far as the science behind it goes is beyond me though.:dontknow:
G
You would probably have good luck with putting a muffler back in. Magnaflow mufflers work good for the money. Just avoid glass pack ones. Magnaflow, Borla, and probably others I'm not thinking about sound better on imports. Flowmaster and ones like it pretty much are made for push rod V8s.basically the car comes out with a cat on each bank (2), then merges to 1, goes through a resonator muffler, then into a silencer muffler at the very back of the car and comes out of that with 2 pipes to the tips. I deleted the last muffler and ran a single pipe from the resonator, to a Y, then out to each tip. Piping is 4ft to each tip from the resonator.
Absorptive Mufflers have poor performance at low frequencies. For absorbing that low freq you need as long straight through muffler that you can fit there. Same thing here that with air duckt muflers, longer are better for low freqs.it is a touch loud along with some anyone resonances between 100-135hz. I am trying to learn if straight through baffle setups can kill these low frequencies or if reflective chambers are the right way?
Lot of info here.
http://en.wikibooks.org/wiki/Engineering_Acoustics/Filter_Design_and_Implementation#Band-Stop_Filter
Ok I think the ball's been rolling on this one so I'm going to move it to Mobile Audio. :T
If you are trying to kill only a certain Hz, you can try to weld on a weight to the pipe. This is done often at the factory to help calm certain frequency's that annoy customers. The size and placement will depend on where you get the most excitement. You need a reed tach or something close to figure it out.
I have seen weights and the theory seems sounds but I am still skeptical that you can really only a small amount of weight to kill nasty notes of high amplitude. It really seems like the pipes that were added might be causing this. If I plug one of them, it totally shuts up. Almost seems like they are interacting with each other. Most like the tuned length of that pipe which is about 4ft which might be the half wave of my nasty frequencies. Dunno
Automotive exhaust acoustics involves the study of sound produced by vehicle exhaust systems. Factors like muffler design, pipe diameter, and resonators affect the sound characteristics. Various techniques such as tuning, sound-absorbing materials, and chambered mufflers are employed to control and enhance the exhaust sound for desired aesthetics and performance.
1 - 14 of 14 Posts
Home Theater Forum and Systems
A forum community dedicated to home theater owners and enthusiasts. Come join the discussion about home audio/video, home theaters, troubleshooting, projects, DIY’s, product reviews and more!
Full Forum Listing
Top Contributors this Month
View All
RobKnapp
12 Replies
briannarichardson2
5 Replies
Da Wiz
4 Replies
Recommended Communities
