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Simplifying Array Design for Sound Systems by Manipulating Heat Through Thermophones

July 14, 2020 by Luke James

Researchers in the UK have reportedly pioneered a new technique to produce arrays of sound by using heat.

Researchers from the University of Exeter in the UK claim to have used devices known as thermophones to create a fully controlled array from a single thin metal film attached to some metal wires.

Traditionally, arrays, which allow sound from several sources to be 'steered' in a certain direction, have been used in a range of normal applications such as ultrasound. Because the sound produced by the sources can be steered in a specific direction, greater control and clarity of sound is gained


Speaker Arrays

Arrays of speakers can be used to shape the sound that they create in the air around them, and an increasing number of applications are now making use of them. These include medical diagnostics, wireless power transfer, and fault detection in materials, among other things.

Conventional speaker arrays rely on sound production through the driven movement of an object, such as a speaker cone. In their study, however, the Exeter researchers claim that they have managed to pioneer arrays of speakers that can produce sound by using heat alone—thermophones. 

Thermophones are nothing new, though; they have been around for a good century or so and boast significant advantages over their mechanical counterparts, such as an absence of moving parts prone to breaking and the ability to be mass-produced from inexpensive and sustainable materials.

Perhaps most crucially of all, particularly for the development of next-generation electronics, they can be made transparent and flexible. However, they have, until now, had limited applications in the real world. 

According to researchers, thermophones could pave the way for simpler array design.

According to researchers, thermophones could pave the way for simpler array design. Image Credit: David Tatnell, EPSRC Centre for Doctoral Training in Meta Materials.


Thermoacoustic Phased Arrays

In their study, the researchers found that thermophones can reproduce the same control over sound fields as traditional arrays when combined into an array. What's more, because they are driven by electrical currents, the sound they produce mirrors the current carriers' movement as they flow through the device. As a result, the sound they produce creates a substantially richer sound field compared to traditional arrays.

According to the research team, their study could pave the way for a much simpler array design because it shows that with thermophone technology, it is possible to create a fully controlled array from nothing more than a thin metal film and metal wires. 

"Using heat to produce sound is a game-changer as it allows us to make speaker arrays smaller than ever before. This, as well as the ability to make the speakers flexible and transparent, has many exciting potential applications, such as haptic feedback systems in smartphones and other wearables," said David Tatnell, the study's lead author. 

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