Audiology Sound Booths- the Great Atlantic Divide

Editor’s Note: Today’s post comes from HHTM’s Dr. Marshall Chasin and was published last month at Hear the Music. We thought our readers at Hearing Views would enjoy the interesting comparison between the North American and European approaches to audiometric test rooms.

By Marshall Chasin, AuD

Look at any North American audiology clinic and you will typically find the client sitting in a sound-treated booth and the audiologist sitting either in an adjacent booth or in a quiet room outside the booth.

This audiology room setup will look familiar to most of our North American readers. Image courtesy
This audiology room setup probably looks familiar to most of our North American readers. Image courtesy

Now, get on a plane and go to Zurich, Berlin, or Florence, and the approach is quite different. Typically you will see one booth, large enough to accommodate the client and the audiologist sitting together.

There are clear advantages and disadvantages to each of these set-ups. The North American approach ensures that pure-tone hearing assessment is performed in as quiet a location as possible (typically less than 35 dBA) without the distraction of a breathing, sniffling audiologist close by. The European approach has the possibility of a greater interaction between audiologist and client.

I must admit that, being trained in North America, I tend to use an audiometric sound-treated booth where I am seated outside in a quiet room. For most of my intervention, the booth is not required in any event. The moment I establish thresholds in the sound booth, it is no longer of any use. I yank the musician out of the booth (typically by saying “get out of the booth!“, because sometimes you need to yell at musicians…) and we go sit by the piano. This is where the real audiology begins.

Even non-piano players can play the piano… at least to the extent that I need them to play. If there is a significant enough hearing loss, I can use my piano to establish dead regions in their cochlea; if two adjacent notes do not sound different, then this is evidence of a cochlear dead region and we should avoid amplifying this frequency region. We can also use the piano to practice playing with and without hearing protection. While patients are playing, we can even drop a probe microphone in their ear canals to verify the function and level of their music in their ears. And if there are no parallel walls- as is sometimes the case in European audiology facilities, the sound quality while playing their own musical instrument is amazing. Few standing waves can add up constructively and destructively to create dead and live regions in the room- a sound recording engineer’s dream.

I have been in several “sound-treated rooms,” mostly in Europe, that have some non-parallel walls. The floor and ceiling are frequently parallel (and both have sound treatment; carpeting or acoustic tiling). The walls, however, can be non-parallel. This has the advantage of minimizing the build-up of acoustic reflections.

This also can make for a wonderful sound recording studio. We don’t want a “dead” sound in our recording- one with minimal reflections; nor do we want a reverberant or overly live sound with too many reflections. Non-parallel walls typically allow some reflections but not too much. This is a nearly perfect environment for recording music or for a person listening through hearing aids.

I recall, in my early years, sound engineers talking about the LEDE concept. This stood for Live End, Dead End and referred to the recording set-up in a “typical” recording room. The loud speaker or musical source would be at the dead end, a part of the room with a lot of absorbent acoustic material, such as drapes or tiling, that would serve to dampen out reflected sound. The live end- the opposite wall of the room-would serve as a highly reflective source and would have a bare wall with no curtains or bookshelves. The LEDE set-up ensured that the “reverberant time” of the room was neither too long nor too short.

Short of designing a room for your clinic that has no parallel walls, the LEDE approach may be better than having nothing but highly reflective parallel sources. I guess we North Americans can still learn a thing or two from our colleagues across the pond.

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