I have a quick question about vibrations. Is there such thing as a natural frequency of the human body? I tried to google some information, but couldn't find anything. The reason for this is that we have a couple of big heat exchangers here at work, and some operators were complaining about noise coming from them. When I got in between them, I could instantly "feel" the sound waves. After taking many vibs measurements, it seemed the frequency was around 100 Hz, with relatively high amplitude. After finishing (which took about an hour), I felt sick to my stomach, and just generally bad. I was wondering if this was around some kind of natural frequency of humans. I mean, it wasn't just the fact that it was low frequency and loud. I mean, I'm sure at some point, we've all known someone who has huge speakers in their cars, but it wasn't like this. Just kinda curious.