Black Raviolis

Buckwheat Pillow: (http://www.target.com/Sobakawa-Buckwheat-Pillow-Off-White-20x15/dp/B000FJQCP8) They are great for sleeping, and I've used them for decades. Never thought of them for audio isolation. HMMM!

I replaced the foam in the headrest of my audio room chair with buckwheat hulls. Quite comfy. I don't think ravioli would be as nice. Haven't tried though...

Adampeter,
It's unfortunate that so many responders above are unfamiliar this product, yet willing contributors...

http://www.innerearmag.com/reviews/accessories/18-1_black_ravioli.html

I use them to great effect:
1) sandwiched between the chassis of my amplifier (solid state) and BDR cones
2) wedged between speaker terminals

The net effect is in noise reduction. More of the finer musical details become exposed.

I have no experience with the effects on tube based equipment.

I've used the buckwheat pillow; noisy when you move your head.
Buckwheat noodles on the other hand can be quite tasty!

Buckwheat pillows are used for a threefold purpose.

Sleeping.

Audio isolation.

Breakfast meal.

Beat that you Black Ravioli suckers.