AudiologyOnline Phone: 800-753-2160


Signia AX Got Better - April 2022

Using Probe Mics to Measure Directionality

H. Gustav Mueller, PhD

January 24, 2001

Share:

Question

How do you use probe microphone measures to assess the integrity of directional microphone hearing aids?

Answer

Probe-microphone measurements could be used to construct a fairly valid ''real-ear polar plot,'' which could show frequency-specific attenuation and the effects of head diffraction and head shadow. This would require a fair amount of work, however, and really is overkill for the everyday fitting of hearing aids. Rather, my thought would be that the average clinician simply would want to use probe-mic measures to assure that the directional microphone hearing aid is working appropriately. When this is the goal, running two REAR curves, one at 0° azimuth and another at 180° azimuth should be all you need (easy to do if patient is in swivel chair). Let's say that you usually fit one of two models of directional instruments, either a Sonotone or a Radioear. After testing four or five different models of the Sonotone, which has a cardiod directional pattern, you find that the typical real-ear front-to-back difference (REAR @ 180° subtracted from the REAR @ 0°) for the 1000 to 4000 Hz range is around 20 dB. The Radioear has a hypercardiod pattern, and the typical front-to-back difference for this product is 15 dB. This gives you some clinic norms to work with. Now, if you're testing a patient with his new digital directional Sonotones and you only see a 5 dB front-to-back difference, you know that something is wrong.

Rather than eyeball the differences in the REAR curves, you might want to have the probe-mic equipment plot the frequency-specific front-to-back difference. If so, then try out this test protocol:

  • Place the patient in a swivel chair.

  • Set the WDRC to ''linear'' (if not, the WDRC processing will work to counteract the effects of the directional microphone, producing results that underestimate directionality in the real world).

  • Use an input signal of 65-70 dB SPL. If you're testing a digital hearing aid, turn off the noise reduction feature, or use test signals designed for assessing digital instruments (e.g., ICRA signals).

  • Turn your patient around so that you conduct the first run with the loudspeaker of the probe system located behind the patient, at a distance of around 3 feet. Tell your probe system that this run is the REUR.

  • Now turn your patient back so that he or she is facing forward and conduct the second run with the loudspeaker located directly in front of the patient. Tell your probe system that this run is the REAR.

  • The probe system will automatically subtract the first run from the second. What is then presented on the monitor is the frequency-specific front-to-back ratio of the directional hearing aid.

  • ____________________________________________________________________

    H. Gustav Mueller, Ph.D. has an audiology consulting practice in Castle Pines Village, Colorado. He is the senior audiology consultant for Siemens Hearing Instruments, Contributing Editor for The Hearing Journal, and teaches audiology classes at Vanderbilt, Central Michigan, Nova Southeastern and Northern Colorado Universities. His publications related to probe-mic measures include:




  •  
  •  
  • Mueller HG, Hawkins DB, Northern JL. Probe Microphone Measurements. Singular Publishing. 1992

  • Mueller, HG. Probe-microphone measurements: Yesterday, today, and tomorrow. The Hearing Journal, 1998, 51, 4: 17-22.

  • Mueller HG, Hall JW. Audiologists' Desk Reference. Singular Publishing, 1988.

  • Mueller, HG. Probe-mic assessment of digital hearing aids? Yes you can! The Hearing Journal, 2001, 54, 1: 10-17.

  • Mueller, HG. Probe microphone measurements: Twenty years later. Trends in Amplication, 2001 (in press).

  •  


h gustav mueller

H. Gustav Mueller, PhD

Professor of Audiology, Vanderbilt University

Dr. H. Gustav Mueller is Professor of Audiology, Vanderbilt University, and has a private consulting practice nestled between the tundra and reality in Bismarck, ND. He is the Senior Audiology consultant for Siemens Hearing Instruments and Contributing Editor for AudiologyOnline. He also holds faculty positions with Central Michigan University, University of Northern Colorado and Rush University. Dr. Mueller is a Founder of the American Academy of Audiology, a Fellow of the ASHA, serves on the Editorial Boards of several audiology journals, and is the Hearing Aids Series Editor for Plural Publishing. Dr. Mueller is an internationally known workshop lecturer, and has published nearly 200 articles and book chapters on diagnostic audiology and hearing aid applications. He is the senior author of the books “Communication Disorders in Aging”, “Probe Microphone Measurements”, and the co-author of the “The Audiologists’ Desk Reference, Volumes I and II


Related Courses

Auditory Wellness: What Clinicians Need to Know
Presented by Brian Taylor, AuD, Barbara Weinstein, PhD
Audio
Signia

Presenters

Brian Taylor, AuDBarbara Weinstein, PhD
Course: #36608Level: Intermediate0.5 Hours
  'Good discussion of importance of outcomes measures and the OTC market'   Read Reviews
As most hearing care professionals know, the functional capabilities of individuals with hearing loss are defined by more than the audiogram. Many of these functional capabilities fall under the rubric, auditory wellness. This podcast will be a discussion between Brian Taylor of Signia and his guest, Barbara Weinstein, professor of audiology at City University of New York. They will outline the concept of auditory wellness, how it can be measured clinically and how properly fitted hearing aids have the potential to improve auditory wellness.

View this Course for FREE.
Need CEUs? Become a AudiologyOnline member to get unlimited CEUs.

Only $99/yr

Learn More

Dynamic Soundscape Processing: Research Supporting Patient Benefit
Presented by Matthias Froehlich, PhD, Katja Freels, Dipl.Eng., Eric Branda, AuD, PhD
Text/Transcript
Signia

Presenters

Matthias Froehlich, PhDKatja Freels, Dipl.Eng.Eric Branda, AuD, PhD
Course: #34060Level: Intermediate1 Hour
  'To the point'   Read Reviews
This paper reviews three different studies conducted with the Signia Xperience hearing aids. Research reviewed for laboratory studies of speech understanding and listening effort, comparative speech-in-noise testing, and real-world EMA assessment of patient benefit and satisfaction.

View this Course for FREE.
Need CEUs? Become a AudiologyOnline member to get unlimited CEUs.

Only $99/yr

Learn More

Moving Beyond the Audiogram Towards a Patient-Centered, Interactive First Fit
Presented by Maja Serman, PhD, Rosa-Linde Fischer, PhD, Rebecca Herbig, AuD, Ronny Hannemann, PhD
Text/Transcript
Signia

Presenters

Maja Serman, PhDRosa-Linde Fischer, PhDRebecca Herbig, AuDRonny Hannemann, PhD
Course: #29711Level: Intermediate1 Hour
  'I've been saying for years that we should be fitting to the patient, not some arbitrary computer-generated target'   Read Reviews
This text addresses the Hearing Profile, a novel hearing aid fitting based on objective and subjective hearing related factors additional to the audiogram, which influence the choice of hearing aid settings. The results from two verification studies showing the benefit of the Hearing Profile for hearing impaired patients are shown and discussed.

View this Course for FREE.
Need CEUs? Become a AudiologyOnline member to get unlimited CEUs.

Only $99/yr

Learn More

Person Centered Goal Setting and Treatment Planning for First Time Help Seekers
Presented by Brian Taylor, AuD
Recorded Webinar
Signia

Presenter

Brian Taylor, AuD
Course: #35089Level: Intermediate1 Hour
  'Great Content'   Read Reviews
The rising popularity of person-centered care involves getting patients actively involved in the goal setting and treatment planning process. This one-hour course reviews specific tactics – conducted both in-person and with remotely technology– that lead to active participation with persons with hearing loss that are seeking help.

View this Course for FREE.
Need CEUs? Become a AudiologyOnline member to get unlimited CEUs.

Only $99/yr

Learn More

Signia Xperience: The Evolution Continues
Presented by Leanne Powers, AuD, Carol Meyers, AuD
Recorded Webinar
Signia

Presenters

Leanne Powers, AuDCarol Meyers, AuD
Course: #33558Level: Intermediate1 Hour
  'Well presented- to the point'   Read Reviews
Creating a natural hearing experience in every situation has been at the forefront of Signia technology. Now we can better understand the environment by using advanced analysis of the acoustical situation and enable individuals to hear what matters to them! Explore the new technology, form factors and applications available on the Xperience platform.

View this Course for FREE.
Need CEUs? Become a AudiologyOnline member to get unlimited CEUs.

Only $99/yr

Learn More

Our site uses cookies to improve your experience. By using our site, you agree to our Privacy Policy.