In consolatione autem loquuntur in aurem

On comfort of In-Ear monitors

In-ear monitors (IEMs) are often considered superior to headphones because of the superior isolation from external noises.  Additionally, because of the small acoustic volume of the ear canal (typically 2cc), high SPL levels, and resulting high bass with low THD, can easily be achieved.  However IEMs can have a reputation for discomfort.  This paper addresses how Periodic Audio Inc. (PAI) addresses this issue.

IEM comfort is most often related to pressure on the tragus and anti-tragus of the ear, on which an IEM would rest when inserted into the ear canal:

https://en.wikipedia.org/wiki/Tragus_(ear)#/media/File:Gray904.png

The tragus and anti-tragus are composed primarily of cartilage and skin.  They flex naturally in and out, but because of their shape (thin depth, wide and tall) are highly resistant to flexure in the vertical dimension.  Thus pressure down on these portions of the ear will cause pain as they are being stressed in ways they do not naturally bend.

There are three typical ways to reduce downward pressure on the tragus and anti-tragus:

  1. Utilize an over-ear mount (memory wire reinforced, or ear hook)
  2. Utilize an inner-ear mount (securing feature that engages the concha)
  3. Minimize weight

Solution 1 is typically seen in most multi-driver IEMs.  Because of the physical size, weight is very high (some weighing in at over 35 grams each).  A hook – either reinforced signal cable or separate component – is used to loop over the top of the ear and support the weight of the IEM.  This solution works, but can cause its own problems with comfort as pressure is now translated to the outside of the ear.  Additionally the hook can interfere with glasses and hats, thus creating other sources of irritation.

Solution 2 is seen in several IEMs.  They typically consist of a soft, silicone rubber “blade” that resides entirely within the concha of the ear.  This stabilizes the IEM in relation to the ear canal; however the pressure of the blade is typically quite high in order to maintain fit of the IEM as well as reducing pressure on tragus/anti-tragus.  In essence, much like solution 1, the problem is simply moved elsewhere rather than addressed.

PAI chooses to use solution 3 on all our IEMs.  We specifically design with extremely lightweight but acoustically dead materials.  Rather than focus on solutions for mitigating the effects of high weight, we choose to design for light weight.  The result is an IEM that – sans cable – typically weighs less than 3.6 grams each.  Extremely light weight means very low pressure on the tragus and anti-tragus, and thus comfort is achieved.

Additionally, we focused on the center of gravity of the IEM relative to the tragus/anti-tragus of a typical wearer.  The center of gravity is positioned slightly inside the “fulcrum” created by the tragus/anti-tragus, so that the majority of the weight is spread evenly between these areas of the ear and the earbud, which resides within the ear canal.  The mass of the metal-injection-molded end cap is to provide enough weight outside the fulcrum such that the balance desired is achieved.

Consideration of comfort is one of the paramount concerns when creating an IEM.  IEMs, by they very nature as extremely compact and portable products, are intended for long-term wear.  IEM wearers can enjoy music in a variety of settings and places that are normally not accessible to music lovers.  By focusing on comfort PAI’s IEMs are designed to support such long-term wear and thereby enhance the opportunites that PAI’s consumers have to listen to music.