# Measuring Vibration

I want to measure the vibration in an environment so that I can isolate some equipment. What is the standard way of measuring this? Basically, I want to mitigate the effects of a nearby train. More important than the loud horn, I need to isolate the equipment from vibrations in the ground. I am looking at some products from newport, but they show resonance around 6Hz. Would vibrations produced by the train be incompatible with these? How can I measure such vibrations? I have some audio microphones and software that shows a spectral distribution, but I don't want to know about the vibrations transmitted through the air as much as I want to understand how much noise is traveling through the concrete floor. I tagged this experimental physics, because it is likely that an experimentalist would have a good answer.

• You could use a seismometer for ground vibrations: en.wikipedia.org/wiki/Seismometer#Teleseismometers. – Ernie Mar 15 '17 at 21:36
• The resonance peak is an inevitable consequence of the way these passive isolators work. The more important fact is that below the resonance frequency, they don't do anything - the transmissibility plot is a flat line at $1.0$. The resonance frequency will depend to some extent on the load that is being supported. As the answer says, first decide what frequencies need to be attenuated and how much attenuation you need. This minusk.com/content/technology/… might be useful (and explore the rest of that website). – alephzero Mar 16 '17 at 7:06

## 1 Answer

There is no need to measure the vibration. The unwanted vibrations must be having some undesirable but detectable effect on the output of your experiment. The effect you are getting compared with what you expect from ideal conditions is a measure of the noise. The improvement in your output signal will tell you what effect anti-vibration materials or techniques is making.

Ground vibrations from trains peak between 4 and 50 Hz. Your anti-vibration strategy should focus on eliminating these frequencies. If your output signal is far from this range, it is unlikely to be affected by railway noise.

A useful exercise is to look at the frequency spectrum of your output signal, using a spectrum analyzer. Some digital oscilloscopes perform this function. The sidebands on the strongest peaks in the signal spectrum will suggest what the frequencies of the major noise sources are. Narrowing of the peaks in the frequency spectrum also shows improvement in your signal.

• Your thoughts, as well as the link, were very helpful. – mrKelley Mar 17 '17 at 20:11