My Saris sounds likes rocks in a garbage disposal until I hit around 340 watts. Then it stops vibrating and is reasonably quiet. Too bad i do all my intervals around 300.

I never thought of using spray foam. Where would you spray it?

Have you tried riding in the small ring?

That vibration at a specific RPM is what's called Natural Frequency. Everything has a specific natural frequency. When something is exposed to its natural frequency, it will go apeshit. The resistance that your unit provides is dependent on the rpm that you are feeding it. So, even if you ride at a faster rpm on your crank at a lower gearing (to achieve the same wattage), it does not matter to the unit. The rpm the trainer unit sees is still the same, to produce the same resistance. You need to change the mass of the flywheel (i'm not familiar with your trainer model), or change whatever that's providing the resistance (electromagnetic, fluid, etc..)
Best advice i would give is to contact the manufacturer. Make a video of the unit in action when it goes apeshit, and send to their customer service.

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Paul..

If this were the case it seems like it would be a serious design flaw to have the first mode of the system such that it is hit with the rpm required for a standard wattage output. No one would buy a kickr. I read the issue as getting worse with higher rpm, not on or off. My vote is for something internal is loose that shouldn't be or a defective unit.

Valid point.
I too would assume that the manufacturer would have run a battery of tests at all levels before mass production.

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Paul..

I reread the post and it does seem to change somewhat with rpm, so not just a linear increase in noise vs frequency like I first assumed. How likely would some internal tolerance/tightness issue be throwing the as designed resonances out of wack? I'm not a ME so I'll stop talking here :x

Thanks for the replies. To clarify the volume of sound definitely gets worse with RPM but is there essentially from the beginning. As ntc and Paul predicted it's not directly linear but definitely also not on/off as if it hit a resonance frequency. It's basically worse the faster you go but also somewhat sporadic.

Regarding contacting customer support- I'm generally loath to contact the manufacturer over these types of issues. Unless I can identify a specific issue it's going to be a waste of time; ST is usually a better root cause endeavor than anyone's customer support (Tacx as an example offered exactly zero help when their Vortex full on bricked on me). If I can't fix it I'll contact them eventually. Was hoping folks had had similar issues and I was overlooking something easy. Seems that's not the case.

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Of course it hurts. The trick is not minding it hurts.

If its relatively new, contact the store that you purchased it from. If the sound is there from the start, it's definitely not a natural frequency thing. Something is loose. Contact Cstomer Support, ask for an email where you can send them a video of the unit in action. Make a video. Send them the video. If the manufacturer truly wants to make a product, they would take this opportunity to see how one of their products failed and use it as a learning experience.

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Paul..