Hi, everyone! It is my first question on this forum.
I live in China. There is a karting track where I go very often for fun. They have both 4 stroke and 2 stroke rental karts, a private karting club, and a private motorcycle club.
The track was built in a suburb of the city and there is a residential area and a college nearby. April, May, and June are the best months for the track and there are a lot of practicing and racing during this time period. Unfortunately, there are also an increase of complaints over the noise emission during the same time period.
An effective solution must be found to reduce the noise emission, or the track has to be closed. I believe the 4 stroke karts do not impose any serious noise emission problem. The noise that residents and students complain about comes primarily from the 2 stroke karts and motorcycles (which seem to be louder than Rotax Max or IAME X30).
Is there any effective approach to reduce the noise emission by 2 stroke karts and motorcycles? How many decibels does it reduce? How much power loss is introduced by the approach?
So far I have just found exhaust pipe mufflers/silencers. How effective are those silencers?
At least for motorcycles, silencers can be very effective! Many tracks here in the United States have imposed decibel restrictions on all vehicles permitted to the track. Many of the newer silencers are efficient too, not robbing too much power from the machines. To me it seems like a no-brainer: quiet racing is better than no racing. People may complain that they have to make an extra purchase if they don’t already have a quiet enough exhaust, but again it’s better than no racing
The 2 stroke karts on this track are primarily Rotax125 Max, IAME X30, and Raket 120 Racing. What specific models of silencer do you recommend for the above engines? I know very little about motorcycles. Still any specific recommendations for motorcycles?
Here’s an example of an additional silencer used with OK karts:
Also, important to note that while the DB levels of your two stroke karts might be higher than the four strokes… Lower frequencies travel further. Something to consider depending on nature of the noise that the neighbors are complaining about.
I’d love to know what good options for trackside remediation are our there
Except that dB output is a function of amplitude (ie. Volume), not Hz. Thus, a 250-4 will be louder than a 125-2. The “2 strokes are louder than 4 strokes” argument is pure myth. Top fuel drag engines red line @ ~10K RPM, but are deafening, unlike a 15K kart motor.
Yeah, the 2-stroke noise issue is probably a consequence of the availability bias somewhat. We don’t really have a scene of race derived 4-strokes so they don’t get attention in terms of noise levels.
We also need to consider the human factor. Just because 4-strokes travel further, is the sound they produce more or less likely to generate complaints. So it is complex. Anecdotally from the MX scene I don’t think the move towards 4-strokes has had a big impact. Some say it made it worse. Hard to know.
There are a multitude of factors beyond the number of strokes, that’s for sure.
One of the most popular noise-reducing trees, the Leyland Cypress will become a tight, dense barrier for view, absorbs sound or wind reduction when planted as a hedge. A very fast growing tree, the Leyland Cypress grows 2 to 3 feet annually, reaching 40 to 60 feet at full maturity when planted in full sun. It’s bright emerald green foliage remains striking year-round and is soft to the touch. It grows very densely, maintaining its slender, conical shape naturally. A belt of trees is the best sound reduction with cypress trees.
