We’ve written a lot about how laboratory instruments are sensitive to vibration and noise. It should be obvious that lab tools are generally more sensitive than people. But it might not be obvious just how sensitive the different tools and processes are. This is just a quick post to put some “order-of-magnitude” numbers on these vibration sensitivities and typical levels.
In this case, we will express “floor vibration” as a velocity. This is simply an expression of how fast the floor is moving at any given vibratory frequency. We could have used displacement or acceleration, but for subtle technical reasons, velocity (in 1/3 octave bands) is usually preferred.
You can express these velocities using micro-meters per second or even decibels referenced to some standard micro-scale velocity. For this exercise, though, it makes sense to look at things in terms of micro-inches per second, which I’ll abbreviate as “uin/sec” (we often use the letter “u” to stand in for “micro”). The reason I like uin/sec for this is that the numbers are all sort of easy to remember. Obviously, you could (or maybe should) use micro-meters/sec, but just by chance, these overall categories tend to fall on the decades when expressed in uin/sec.
So, here is a rundown of the orders-of-magnitude vibration levels that you might come across in real buildings:
100,000s of uin/sec: inappropriate nearly everywhere
deeply uncomfortable to humans
potentially damaging to structures
10,000s of uin/sec: macroscale vibration
strongly perceptible to people and animals
probably annoying (depending on setting + level)
1,000s of uin/sec: interface between human-scale and lab-scale levels
typical for upper floors in buildings (including labs)
high thousands: distinctly perceptible to people
mid thousands: near the threshold of perception for humans
mid thousands: relevant to modestly-sensitive technical uses
low thousands: truly “lab-relevant” vibration levels
notably, the “VC Curves” begin at 2,000 uin/sec (VC-A)
100s of uin/sec: high-end instrument-scale vibration
necessary for lots of sensitive tools
very expensive to achieve on upper floors
in “VC” terms, VC-D is 250 uin/sec (6.3 um/sec)
10s of uin/sec: contemporary nanotech-scale vibration
needed by cutting edge SEM/TEM imaging
typically unrealistic to achieve on upper floors
in “VC” terms, VC-G is 32 uin/sec (0.8 um/sec)
single-digit uin/sec: exceptionally quiet
difficult to achieve anywhere without exotic structures
desirable for some emerging technologies
There’s a lot going on in the “thousands of micro-inches/second”: this is the regime where human sensibilities give way to instrument sensitivities. It’s also where a lot of opportunity can be found in laboratory design. Meanwhile, at the low-end of the scale, cutting-edge research currently demands levels in the “tens” of micro-inches/second, especially for high-end imaging.
But for now the lesson is simple: human vibration sensitivities are middling, and lots of high-tech laboratory tools are far, far more sensitive to building vibrations.
Contact us if you need help designing new buildings or renovating old ones for laboratory uses. We have consulting experience with vibration design in both new construction as well as retrofits, and we can help make your product or project more successful.