I meant to answer this yesterday, but work got in the way. I am very new, but have a RS&Boom myself, so hope I can help a little.
As I said, I am a relative novice at this, but there are a few good threads on Shake placement here, and on the old Google Groups Raspberry Shake group site. I read a lot of them when I got my shake this past Christmas. I encourage you to do the same. There are lots of ideas.
If you don’t choose to build a seismic vault in the ground, I think having the shake on a concrete floor which is at ground level is the best option overall. Placing the shake on a carpet, even with a metal plate or concrete paver under it, will still transmit unneeded vibration to the unit because you cannot place enough weight atop the shake to cancel out the effect of the fibers underneath, which will shift over time, and provide only a semi-solid surface. That doesn’t mean it will not work. Detections are very possible in that state, but the strength of the quakes will have to be higher.
I started off in my basement, on the concrete slab, next to a structural I-beam, since that was the recommendation. While this was an OK location, it turned out not to be best, because that location was too near the furnace/AC with it’s fans, water pipes, a sump pump, and the water heater. All sources of intermittent noise, and just devastating for the Boom, which was mostly deafened. In addition, the movement of the family on the two floors above was transmitted through the structure into the I-beam and other parts of the house, meaning the device had too many periods of high velocity (noise). I spent a lot of time playing with positioning and sound damping at that location, but decided eventually there was just too much ambient noise.
So, I moved my S&B to my garage floor. Again, this is a concrete slab directly atop the ground. I wasn’t sure this was going to help, because the garage adjoins the kitchen, which is always the most trafficked area of any home, but it turns out to be an excellent location for me. Overall, there is little traffic above this location because that part of house is empty most of the time (it’s a bedroom), and we do not park our cars in the garage most of the time. So, except for the occasional grocery run and moving the garbage cans for pickup, this area remains relatively quiet. I immediately saw a huge decrease in average noise level, dropping from an average resting velocity rate of 4uM/s to .4UMs, and even lower during quiet periods. I don’t know what this translates to in signal capture, but I suspect it made my lowest possible quake capture drop from the 6.0 range to the 5.0 range, over the same distance, which, given the magnitude scale, is a pretty impressive increase. This doesn’t mean I can pick up every quake at the lowest range, but I don’t think it would have been possible to capture any sub-6.0 quakes prior to the move.
Once I felt satisfied that I had a good location, I’ve looked at other things to improve my sensitivity. For what they are worth, I’ll throw them out, but will likely hear from others who do not think they are worth the effort, so your results may vary. I started with the base assumption that a quiet location was great, and a vault would be better, but am not ready in the winter to dig a hole. So, what could I do to improve my signal to noise ratio - the value of signal I am receiving above whatever ambient noise level I have in my system?
First point, there is a level below which you cannot go with the R-Shakes. There is a certain amount of digital noise that is an artifact of the system beyond which you will not be able to gain any value, but it’s generally much lower than a hobbyist can achieve. With that understood, my thoughts were that these are very very sensitive devices. If I can receive the micro-micro-micro changes in the ground from a quake on the other side of the world, then they are likely susceptible to even tiny vibrations in the local environment. With that in mind, I set out looking at sources of noise that might affect the RS&B in its environment in my garage. Since I have a background in Radio Frequency work, some of this came to me naturally, because many of the same principles apply. First, I wanted to make sure that the shake itself was well-mated to the concrete it was on, so I did minor things like making sure the cement surface was spotless, so sweeping and a good wipe was the first order of the day. I made sure that where the legs (properly leveled) were placed, they were on solid cement, and not in a pit or divot. A magnifying glass helped here.
Second, I purchased one of these https://www.amazon.com/gp/product/B002UL9ZEO/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 and placed it atop the shake, to dampen any vibration the enclosure might pick up and transmit to the Geophone. I saw replicable positive effect from this.
I also looked for things that might pick up sympathetic vibrations in the environment, and did whatever I could to reduce those. This was minor housekeeping, like tightly dressing the cables connected to the shake, so none of them were coiled in the air and wiggling from other vibrations. I used gaffer’s tape to make sure they were all tight to the floor and at the same time not pulling the shake in one direction or the other.
Finally, I have a metal enclosure atop my shake to prevent Radio interference (I am a Ham Radio operator) so I also weighted that enclosure with a 2nd weight, and sealed it’s edges so it doesn’t have a point of vibration at any side.
Did all this help? Yes, I can report that it did. I have reasonably decent noise levels now, much better on average than initially, and I routinely pick up quakes in the 5.7 and above range from across the world, and local quakes out to about a 1K miles at much lower strengths. My boom is also useful now, since it’s in a better environment, and I frequently pick up passing Helicopters, planes, large vehicles, and the occasional explosion from the military base about 35 miles from here (Quantico). I’m pretty happy.
I hope this helps give you some ideas, and feel free to ask any other questions you might have, with the understanding I am still new to this game.
Edit: I may have underestimated my Shake, because today I copied the 5.5 in Indonesia at 10,000 miles.