Alternative transducer technologies including thermoacoustic technology for headphones

Thermoacoustic technology

The thermoacoustic effect makes sound by heating the conductor at an audio frequency, an effect that is not magnetic and does not vibrate the speaker. A research group at Tsinghua University created a carbon nanotube thin-yarn earphone based on the thermoacoustic process in 2013. A CNT thin yarn thermoacoustic chip is a functioning element of the as-produced CNT thin yarn earphone. A chip of this type is constructed up of a layer of CNT thin yarn array supported by a silicon wafer, and periodic grooves of a particular depth are formed on the wafer using micro-fabrication technologies to prevent heat leaking from the CNT yarn to the substrate.

Other transducer technologies

Heil Air Motion Transformer (AMT); Piezoelectric film; Ribbon planar magnetic; Magnetostriction; and Plasma or Ionic are some of the less prevalent transducer technologies used in headphones. ESS Laboratories offered the first Heil AMT headphone, which was effectively an ESS AMT tweeter from one of the company's speakers operated at full range. Only Precide of Switzerland has produced AMT headphones since the turn of the century. Pioneer pioneered the use of piezoelectric film headphones, which used a flat sheet of film to limit the maximum volume of air movement. TakeT currently manufactures a piezoelectric film headphone with a transducer that folds over the diaphragm that is formed similarly to an AMT transducer. It additionally incorporates a two-way design by its inclusion of a dedicated tweeter/super tweeter panel. The folded shape of a diaphragm allows a transducer with a larger surface area to fit within smaller space constraints. With that radiating area, this increases the total volume of air that may be pushed on each transducer excursion. Because of the limited volume of air in a headphone, a plasma or ionic transducer can become a full-range driver; nevertheless, the high temperatures and voltages of these types make them extremely rare, with only the Plasmasonic being commercially available.

Magnetostriction headphones, often known as Bonephones, work by vibrating against the side of the skull and transmitting sound by bone conduction. This is especially useful in settings where the ears must be kept clear, or for those who are deaf for causes other than the neurological apparatus of hearing. Magnetostriction headphones, on the other hand, have worse fidelity when compared to traditional headphones, which rely on the regular workings of the ear. Also, in the mid-1980s, a French business called Audio Reference attempted to market Henri Bondar's Plasmasonic plasma headphones. There are no known operational examples. Because of the limited amount of air in a headphone, a plasma or ionic transducer can become a full-range driver, however, they are extremely rare due to the high temperatures and voltages required.