Found this today:
http://books.google.com/books?id=EK0...tremor&f=false
Table 1 - Tremor Frequencies
2.5-5 Hz
Cerebellar tremor, Holmes tremor
3-6 Hz
7-9 Hz
Essential tremor, postural tremor in parkinsonism
7-12 Hz
Physiological tremor, exaggerated physiological tremor
12-18 Hz