Audiologist Hans Mülder shares his all-time favorite publication that can help you better understand the limitations and advantages of adaptive procedures.
When it comes to scientific publications, they can be a mixed bag. And you’ll probably forget most of the ones you read over the years.
But not always.
There are some publications, and some articles, that will stand out in your memory for their shining brilliance, creative thinking, or clear argumentation.
One article that I will never forget, and still refer back to, is ‘Transformed Up-Down Methods in Psychoacoustics’, published by Harry Levitt. Believe it or not, it was published five decades ago in the Journal of Acoustical Society of America . . . and it is still as relevant today as it was half a century ago.
Why? It does a great job of helping readers understand the limitations and advantages of adaptive procedures. If you are interested in psychoacoustics this is an article you’ll find yourself referring back to again and again.
The article is so helpful because it:
- Describes the fundamental mathematical and psychological aspects of adaptive testing procedures. In adaptive testing the level of the next stimulus depends on the correctness of the reply to the previous stimulus.
- Includes guidance on speech-in-noise testing. Patient instructions, step size, starting point, criteria for making the next stimulus harder or easier; it is all there.
- Describes the basic assumptions that we make when we do adaptive testing. One of those is that psychometric function is stationary with time (i.e. there is no change in the shape or location of the function during the course of a test). This is usually not a problem if you do diagnostic speech-in-noise testing, in free field or under headphones.
- Explains what is a no-go in aided testing. For aided testing there is a clear no-go for adaptive testing as today’s hearing solutions have many adaptive features, some of which feature long time constants of 10, 30 and even more seconds.
Some of these slowly adapting hearing aid and remote microphone behaviors you may not be aware of, they may not have been published or marketed by the manufacturer, and you cannot program or disable these.
This is not to say these features are wrong. On the contrary, most likely they are very beneficial. It only means you cannot do any adaptive speech-in-noise testing with a patient wearing hearing aids, a CI or using remote microphone technology.
Correct implementation avoids a common mistake
In the ‘American Academy of Audiology Clinical Practice Guidelines Remote Microphone Hearing Assistance Technologies for Children and Youth, from Birth to 21 Years’, their clinical guidelines clearly support Levitt’s paper.
In paragraph ‘SA1.5.3. Not recommended’ it says that no adaptive testing, like the popular HINT, HINT-C, BKB-SIN, Quick-SIN, should be done with remote microphone technology.
This is an important learning because in practice I still see some colleagues do adaptive testing with remote microphone technology, and you can also still find this in publications as part of test protocols.
Since the launch of Dynamic FM by Phonak and later in 2013 when Roger™ was launched, wireless microphone technology includes dynamic or what we now call adaptive behavior. Of course you can do an adaptive speech-in-noise test with a patient wearing a Roger system, but I believe the result is completely meaningless. No matter what, full stop.
After reading Levitt’s publication, I hope that the next time you perform an adaptive test procedure, you will fulfill his boundary conditions. Until then I’d love to hear what your all-time favorite audiology publication is!
- Levitt, H. (1971). Transformed up-down methods in Psychoacoustics. Journal of the Acoustical Society of America, Volume 49, Number 2 (Part 2). Retrieved from Transformed Up-down Methods in Psychoacoustics (stanford.edu).
- American Academy of Audiology (2011). American Academy of Audiology clinical practice guidelines remote microphone hearing assistance technologies for children and youth, from birth to 21 years (Supplement A). Retrieved from http://successforkidswithhearingloss.com/wp-content/uploads/2013/08/HAT_Guidelines_Supplement_A.pdf.