Tactile sound is the sensation of sound transmitted directly to the human body by contact, rather than by sound waves through the ears. For example, when you stand on a train platform you can feel the train approaching as well as hearing it. Explosions, crashes, sonic booms, and thunder are all normally felt in addition to being heard. Tactile sound is also present in the vibratory signature of musical instruments, your automobile, in aircraft, someone walking across the floor or slamming a door, even the vibration from the compressor in your refrigerator. When we talk we experience our voice in a tactile format, if we are in intimate contact with a talking individual, we can feel their voice. Besides air pressure, tactile sound can be conducted through ground motion. Tactile sound can also be transmitted through water, for example in a swimming pool or hot tub.
In addition to being produced naturally, tactile sound can be produced by a transducer in the same way that sound can be produced through a loudspeaker. Tactile sound has been used by the military for flight and tank simulators, for rides in amusement parks, medical research, musical tactile massage, home cinema, computer games, car audio, dance floors, water beds, patio decks and for musical performance as tactile feedback for drummers and other musicians. It has even been used recently to promote weight loss,improve muscle tone and improve blood circulation by a resistance training company.
Various designs for tactile transducers have been presented since the 1960s, most of which fall under the "shaker" category. Shakers create a vigorous vibration by moving a mass (usually a magnet) which is bolted to a final mass (like a chair or couch). A simple example of this is the vibration available on a common cellphone. Another way of producing tactile sound uses "linear actuators", which move furniture (usually up and down), rather than shaking it. The main advantage of linear actuators is that they deliver actual motion (ground excursion), not just vibration.
A tactile transducer or "bass shaker" is a device which is made on the principle that low bass frequencies can be felt as well as heard. A shaker transmits low-frequency vibrations into various surfaces so that they can be felt by people. This is called tactile sound. Tactile transducers may augment or in some cases substitute for a subwoofer.
A bass-shaker is meant to be firmly attached to some surface such as a seat, couch or floor. The shaker houses a small weight which is driven by a voice coil similar to those found in dynamic loudspeakers. The voice-coil is driven by a low-frequency audio signal from an amplifier; common shakers typically handle 25 to 50 watts of amplifier power. The voice coil exerts force on both the weight and the body of the shaker, with the latter forces being transmitted into the mounting surface.
Tactile transducers may be used in a home theater, a commercial movie theater, or for special effects in an arcade game, amusement park ride or other application.
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