[Editorial] A New Era of Headphone Listening? Here's Cartilage Conduction!

March 2025 Editorial

The beginning of a new era of earphone listening!

Author: Lucio Cadeddu - TNT-Audio Italy
Published: March, 2025

There are at least two ways to listen: the traditional one through the ear canal and the eardrum and the one through the bones of the skull. If you have had an ENT visit recently (do it!), you might have noticed that, in addition to the usual audiometry through the use of closed headphones, the doctor checks the functionality of the acoustic nerve through the stimulation of the bones of the skull. The vibrations are perceived as sounds and frequencies absolutely similar to those heard with headphones.

In 2004, Professor Hiroshi Hosoi of Nara Medical University (Japan) discovered a third way to transmit sound to our auditory system, through cartilage conduction, or conduction by stimulation of the cartilage near the ear canal. A vibrating device causes the cartilage to oscillate, and thus the sound generated in the external auditory canal is transmitted through the eardrum, the middle ear, and the inner ear. In this case, the cartilaginous part of the external auditory canal plays the role of the diaphragm of a loudspeaker.

[Audio-Technica ATH500BT2]

The potential benefits are numerous:

Unlike traditional earphones, cartilage conduction earphones can be used without blocking the external auditory canal, so the user does not feel their own chewing and does not have the sensation of a blocked ear, typical with traditional earphones;
less sound loss compared to open earphones;
the output volume of the sound conducted through the cartilage can be varied by adjusting the force of application on the external ear, which can be done simply with a smartphone;
the transducer can be positioned on the frame of glasses;
it can be used in water at a depth of 4 m;
it does not cause inflammation or otitis, since the auditory canal does not get harmed in any way.

Compared to a bone conduction transducer, it consumes less energy (vibrating the bones of the skull requires more energy). Moreover, since the bone transducer must be pressed on the mastoid with a force greater than 1 Newton, long-term use can cause skin irritation, lasting depressions in the skin, and discomfort. A bone conduction device cannot produce appropriate timing and intensity intervals between the left and right ears when used binaurally. For this reason, stereophonic use is not optimal. Vice versa, a cartilage conduction device can produce sounds independently in the left and right ear, thus allowing precise sound localization.

The company CCH-Sound Inc. holds most of the patents related to this new technology and also produces the so-called CCH transducers. The first headphones to use such a system appeared on the market a couple of years ago and were the Audio-Technica ATH-CC500BT whose frequency response was claimed to be between 25 and 22,000 Hz. Now a completely revised version has been released, the ATH-CC500BT2, which is more sensitive and lighter, and uses Bluetooth 5.3 transmission. The cost is €139 but it is not yet available in the classic on-line stores (as of today, March 2025). It seems to be available on the Audio-Technica website, and on this Ebay store (€153 including shipping).

When it becomes possible, we will try to have a sample to test, because the idea of freeing oneself from the slavery of earphones (and traditional headphones) is particularly tempting.

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