Has anyone here installed or built your own Helmholtz resonators or 1/4 wave resonators? I've read about it on other forums as an effective method of cutting drone at a specific frequency. I love the sound of my Borla Stingers, the drone is just pretty bad on the highway.

Searched here and couldn't find any mention of them. I mean I know it has to work, it just a matter of getting the proper length/volume.

For those unfamiliar with the subject:
http://www.performancetrucks.net/for...-drone-489463/

 

it's a bit dry since it's more or less a textbook, but Acoustics by Leo Beranek goes into the theory and design of resonators. They're actually pretty simple with some basic math needed to design an appropriate one.

 

Thank you for that. I have been able to find some useful information via the all-powerful Google.

As a side note, and article I stumbled across may provide an explanation to others as to why traditional inline resonators may not provide the desired reduction in drone they wish for:

"In a Helmholtz resonator design a cavity is attached to the exhaust pipe. At a specific frequency the cavity will resonate and the waves in the exhaust pipe are reflected back towards the source. However there are also pass band frequencies where the resonator has no effect and so resonator muffler design is targeted to specific frequencies where the majority of the attenuation is required. In some designs, the muffler has several resonators of different sizes to target a range of frequencies.
Expansion chamber mufflers reflect waves by introducing a sudden change in cross sectional area in the pipe. They do not have the high attenuation of the Hemholtz resonator, but have a broadband frequency characteristic, with pass bands when half the acoustic wavelength equals the cavity length. Their performance also deteriorates at higher frequencies when the cross axis dimension of the muffler is 82% of the acoustic wavelength (Davis, Stokes, Moore and Stevens [5]). Some expansion chamber muffler systems are also packed with sound absorbing material which helps to improve the high frequency attenuation. "

http://www.paraglidingteam.nl/PPGTec...1155795969.pdf