The banner above is an advertisment - if it asks you to download software, please ignore.
Site News - 7/1: Members: Log In to See Fewer Ads! | 5/28: SAAB Evolutions/TSN T-Shirts $14
[General | Members | C900 | 9000 | NG900 & OG93 | 93 | 95 | NG95 | 99 | Sonett | Vintage Models | Clubs | Other Cars | FAQs | Gifts | Member Photo Galleries | Member Directory | Classifieds | Manuals | *Buddy Registry | *Mileage Registry | Polls | What's New | Raffle | Photo of the Month | Sponsors]

Performance Bulletin Board
[Subscribe to Daily Digest]
(Search Author's Posts: e.g. Keyword:username)*Members Only

[Main Performance Bulletin Board | BBFAQ | Prev by Date | Next by Date | Post Followup ] Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos
some friends and I conjectured once that
Like This Post: - Subscribe to Daily Digest for this Bulletin Board
Posted by nt moore (more from nt moore) on Thu, 3 Jul 2003 09:19:40 Share Post by Email
In Reply to: What exactly is a glass pack and what will it do..., Chad, Thu, 3 Jul 2003 06:53:15
Alert me when someone posts in this thread:
Members do not see ads below this line. - Help Keep This Site Online - Signup

some firends and I made a few conjectures once about a glass-pack muffler. We assume that it is basically a pair of concentric cylinders with fiberglass packed between inner and outer shells. We also assumed that the inner shell is perforated.

If this is the correct setup (think of a coffee can as outer shell, campbells soup can as inner shell, steel wool stuffed between two cans, and the campbells soup can looking like it has been hit with buckshot a couple of times), then the following analysis applies.

Soundwaves propagate from the exhaust manifold in pulses. These pulses (or oscillations in air density) are traveling waves, and there are many different wavelengths present (think of a fourier series). When a high pressure node occurs in a solid pipe its propagation continues unobstructed. When the same node (reigon of high pressure exhaust gas) occurs near a hole in the soup can, the pressure excites the insulation (heats it up, moves it around) and that sound wave loses energy.

The net effect is that any sound wave with wavelength shorter than the length of the glass pack reigon will be filtered out. This is similar to a band-pass filter in electronics. Two generalizations can be drawn:
(1) as the muffler is lengthened the emitted sound becomes lower in average pitch.
(2) dampening (filtering out) of higher pitch frequencies increases as the sound absorbancy of the packing matieral increases in quality.

NT

posted by 128.101.25...
Posts in this Thread:
Alert me when someone posts in this thread:
Members do not see ads below this line. - Help Keep This Site Online - Signup
Post a Followup

No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.

Name: Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos
E-Mail: (Optional)
Re-Enter E-Mail: (Confidential & Secure - Not revealed to other users!)
Note: Please check your spam folder for BB responses.

Subject:

Posting rules are simple - No for sale/wanted ads may be posted here - use the site classifieds.
You may not cross-post your message to multiple BBs.
Not permitted: political/religious topics and being disrespectful (personal attacks, insults, etc...).
 Site Members do not see any red text, inline ad links, bottom of page anchor ads, box ads, or anti-spam check.

Message: (please no for sale/wanted classifieds - post those in the Saabnet.com Classifieds)
Links are now automatically made active, no need for any special code (or use the Option Link field below) - don't put links in () or end with a '.'
To add inline images to your post, use [img]http://www.domain.com/img.jpg[endimg] (or use the Optional Image Link field below).

Links are now automatically made active, no need for any special code (or use the Option Link field below) - don't put links in () or end with a '.'
To add inline images to your post above, use [img]http://www.domain.com/img.jpg[endimg] (or use the Optional Image Link field below).
Optional Link: (e.g. http://www.saabnet.com/)
Link Title: (Optional)
Optional Photo/Image Link: (e.g. http://www.saabnet.com/img.jpg)
Photo/Image to Upload: (Please be patient while file uploads)



StateOfNine.com
SaabClub.com
Jak Stoll Performance
M Car Covers
Ad Available

The content on this site may not be republished without permission. Copyright © 1988-2024 - The Saab Network - saabnet.com.
For usage guidelines, see the Mission & Privacy Notice.
[Contact | Site Map | Saabnet.com on Facebook | Saabnet.com on Twitter | Shop Amazon via TSN | Site Donations]

Random Saabnet.com Member Gallery Photos (Click Image)
This is a moderated bulletin board - Posting is a privilege, not a right. Unsolicited commercial postings are not allowed (no spam). Please, no For Sale or Wanted postings, SERIOUSLY. Classifieds are to be listed in The Saab Network Classifieds pages. This is a problem solving forum for over 250,000 Saab owners, so expect to see problems discussed here even though our cars are generally very reliable. This is not an anything goes type of forum. Saabnet.com has been a moderated forum since 1988. For usage guidelines, see the Saabnet.com Mission and Purpose Page. Please remember that you are not anonymous. Site Contact | Site Donations | Other Sites by SP - Poverty2Prosperity.org | Run Club Menlo Park | ScreenBot


Site Members do not see red text instructions, bottom of the page anchor ads, or box ads.
Click here to see all the Site Membership Benefits!