Voice Coil Actuators

A voice coil actuator consists of a current carrying coil interacting with a permanent magnet. They received their name due to their common use in audio loudspeakers. Voice coils are also commonly used in the read/write heads of computer hard drives.

While they are in some ways similar to solenoids, they have several useful differences. First, reversing the current flow in the coil causes a reversal in the interaction with the field of the permanent magnet. This allows for the voice coil to move in both directions. Second, the displacement of the voice coil is proportional to the current in the coil. These two properties allow for the production of positive and negative air pressure variations of varying amplitude, as in a loudspeaker. The proportionality of the movement of the voice coil allows its use for the accurate positioning necessary for computer hard drives1).

Principles of Operation

Voice coils typically consist of a non-magnetic center pole, a cylindrical coil connected to the power supply, and an outer cylindrical permanent magnet. The current running through the coil creates a magnetic field, which interacts with the field established by the permanent magnet.

Voice Coil Applications

Some of the earliest designs of voice coils came from loudspeakers. The majority of loudspeakers are still constructed with voice coils2). The design of a speaker system relies as much upon the speaker enclosure as the speaker driver3).

Computer hard drives use voice coils for the positioning of read/write heads4).

D. Birnbaum's breakflute uses voice coils placed in the toneholes of a flute. When the performer's fingers are placed on the toneholes the voice coils give haptic signals to their fingertips5).

Voice coils have been used to provide vibrotactile feedback. The device used by Giordana and Wanderley varies from the standard voice coil design in that the permanent magnet is the moving element and floats freely inside the coil6).

Arrays of voice coils have been used for the creation of tactile displays7).


Brauer, John R. Magnetic Actuators and Sensors. John Riley and Sons, Hoboken, NJ:2006.
Gogue, George P. Voice-Coil Actuators, accessed March 23, 2012.
Dickason, Vance. Loudspeaker Design Cookbook. Audio Amateur Press, Vernon, CT:2006
Georg Pelz, “Designing Circuits for Disk Drives,” Computer Design, International Conference on, p. 0256, 2001 IEEE International Conference on Computer Design (ICCD'01), 2001.
Marcello Giordano and Marcelo M. Wanderley. “A Learning Interface for Novice Guitar Players using Vibrotactile Stimulation.” In Proceedings of the 8th Sound and Music Computing Conference, Padova, Italy, 2011.
Luv Kohli, Masataka Niwa, Haruo Noma, Kenji Susami, Kenichi Hosaka, Yasuyuki Yanagida, Robert W. Lindeman, Yuichiro Kume, “Towards Effective Information Display Using Vibrotactile Apparent Motion,” Haptic Interfaces for Virtual Environment and Teleoperator Systems, International Symposium on, p. 68, 2006 International Symposium on Haptic Interfaces for Virtual Environment and Teleoperator Systems (HAPTICS'06), 2006.