Why one earplug is not like another earplug

Ian O’Brien has been a guest blogger for us in the past and we are glad to welcome him back.  Ian hails from Australia (and I was tempted to put his picture upside down but didn’t think anyone would get my humor).  He has a couple of master’s degrees (music and audiology) and is working hard on his PhD at the University of Sydney.  Ian was able to send this to us as he sat at the Dallas-Fort Worth airport en route home after having given a talk at the National Hearing Conservation Association (NHCA) in Florida.

Ian O'Brien
Ian O’Brien

As both a performing musician and an audiologist I get to try a lot of different styles of earplugs. I must have two dozen sets of custom-molded this and that going back to 1988, all of which I have given a good go in various orchestras, stage shows and musicals I have worked for over the years. I have also fit many, many more to musicians of pretty much every instrument imaginable.

The musicians’ plugs I have come across that really don’t do the job they are intended (i.e. reduce the volume to a reasonable level while maintaining an ability to play and communicate musically with those around you) tend to have one (or more) of the following problems:

-over-attenuation

-occlusion (particularly for the double reeds and brass)

-discomfort, poor fit, shrinkage, cracking mold

-seal breaks when singing or playing

-lack of high frequency response/unnatural sound

Over-attenuation

I talked about over-attenuation in my last guest blog for Marshall so I’ll just briefly mention it as one of the main causes musicians – particularly orchestral musicians – don’t use their earplugs. Before you recommend 15, 20 or 25dB over 9 or 10dB, estimate exposure levels and durations to make sure you aren’t unnecessarily isolating the musician.

Occlusion

Occlusion affects any musician whose instrument contacts their head in any way.  Those who play instruments such as cello, double bass, percussion, guitar/s or keyboards suffer from occlusion only when they try to have a conversation with occluding earplugs in place.  For many musicians their first experience with earplugs is either using industrial or a generic-fit style of plugs and (as first impressions tend to last).  Audiologists are familiar with occlusion and are quick to recognize what is going on when musicians use words like ‘buzzing’, ‘booming’, ‘rattling’ or phrases like ‘I can’t hear a thing over the sound of my own horn’.  Most audiologists who have fit more than a couple of custom hearing aid molds are well aware of the issue and the technique of reaching the second bend or the bony cartilage in the ear canal to minimize occlusion, which Marshall has written about at some length in the past.  There are also some relatively recently developed filters popular in Europe that significantly reduce occlusion using mechanical means without the very deep molding that other filters may require. These are well worth further investigation.  We have recently fit an orchestra with these plugs ‘down under’ and are having good success so far.  This same filter has also been released as a generic fit.

Discomfort, poor fit, shrinkage, cracking mold

The first few years of my professional playing career I thought earplugs were necessarily hard and uncomfortable and that this was something I had to get used to.  I also thought that degrading, discoloring and shrinking after a year or two was inevitable.  It wasn’t until I began researching and investigating alternatives that I discovered the plugs I had been using were made using silicone with that was too hard.  To account for large amount of movement in the ear canal that singers, wind and brass often exhibit while playing, the material the plugs are made from needs to be relatively pliable to maintain both comfort and an acoustic seal.  If it is too pliable, on the other hand, it tends to be hard to insert and will split over time. After discussion with various manufacturers it is my firm opinion that musicians’ plugs should ideally be made from shore 40 silicone, similar to that used in the nipples of baby’s bottles.  While using this softness means very little alteration/grinding to the mold is possible after manufacture, the benefits to the musician and the longevity of the earplug far outweigh the inconvenience of the occasional ‘send-back’.

Poor high frequency response/unnatural sound

This is a common complaint from musicians.  While no passive earplug that I have heard is ‘perfect’ to my ears with regard to high frequency response, some fall far short of the mark.  This could be for a fairly simple reason – they haven’t been ‘tuned’ correctly!  Earplugs destroy the natural resonance of the concha and the ear canal, which impart a good amount of high frequency amplification when left open.  To address this it is necessary for the manufacturer of the mold itself (not the filter) to ‘tune’ the sound bore .  A good manufacturer will use a mass meter to test the sound bore’s resonance in each earplug and ensure that they are suitably shaped to impart sufficient high frequency gain to make up for the lost outer-ear amplification.  If you would like to supply great sounding earplugs, it is important to ensure that your supplier is attending to this crucial detail or whether they are simply drilling a parallel sound bore – this is usually observable both visually and through simple insertion loss measures described by Marshall previously.  This step really makes a difference to the musicians’ timbral perception.

In addition to this, emerging ‘active’ earplugs are attempting to address the problem using amplification, and are showing a great deal of promise.

Playing and performing with earplugs requires skills musicians need to develop over time, similar to other aspects of instrumental playing.  While it is really important to help musicians you are fitting understand this and to stress that they will inevitably need to accept some compromises, it is also critical they be given the best chance of having (and giving) positive and musically meaningful experiences while still protecting their hearing.  Adopting some of the above strategies may help make this happen and your music client will not only thank you, they’ll recommend you to their colleagues and students.

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About Marshall Chasin

Marshall Chasin, AuD, is a clinical and research audiologist who has a special interest in the prevention of hearing loss for musicians, as well as the treatment of those who have hearing loss. I have other special interests such as clarinet and karate, but those may come out in the blog over time.

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Wayne Staab

Good article. The only thing is that I wish people would use the occlusion effect instead of the word occlusion. These are two different experiences. In this article, occlusion effect would be the understood experience.

Bill Schachter

Great articles! As a musician also, I hum a lot, hoping to revive my ear nerves. But I recently bought. A new electronic keyboard and noticed that notes above c2 are distorted. I have to assume the correct note is
Playing but I do not believe it. And, yes, I use phonic. BTE aids .