What are the typical frequencies at which vibrators vibrate?

Frequency analysis of commercially available vibrators. Turnbull GI, Ross LC, Peacock JB. The tonic vibration reflex -- elicitation of a muscle contraction by mechanical vibration -- is a well documented physiological phenomenon of particular relevance to physiotherapy. read more

The string is connected to a vibrator (of constant frequency f), and the length of the string between point P and the pulley is L=2.00 m. When the mass m is either 15.9 kg or 24.8 kg, standing waves are observed; however no standing waves are observed with any mass between these values. read more