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 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.
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
- distinctly perceptible to people
- possibly annoying (depending on setting + level)
- 1,000s of uin/sec: human-scale vibration
- typical for upper floors in buildings
- both for offices and for routine labs
- 100s of uin/sec: instrument-scale vibration
- necessary for lots of sensitive tools
- expensive to achieve on upper floors
- 10s of uin/sec: contemporary nanotech-scale vibration
- needed by cutting edge imaging like SEM/TEM
- unrealistic on upper floors
- single-digit uin/sec: exceptionally quiet
- difficult to achieve anywhere
- desirable for some emerging technologies
We’ll expand some on these different orders-of-magnitude in future postings. In particular, 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.
But for now the lesson is simple: human vibration sensitivities are middling, and lots of high-tech laboratory tools are 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.