Optimum Audiology and Dr. Mendoza has been doing Real Ear Measurements (REM, Probe testing) for the past 25 years. Dr. Mendoza was trained by Gustav Mueller, Ph.D. who continues to be a leader in this technology. This article describes a great amount of information about Real Ear Measurement/Probe Testing and was written by her colleague and mentor, Dr. Mueller (https://journals.sagepub.com/doi/10.1177/108471380100500202).
Probe-microphone testing was conducted in the laboratory as early as the 1940s but it was not until the late 1970s that a less cumbersome system was available for testing hearing aids in the patient's ear but it was not widely used due to the cost and limited availability of the instrumentation. It was mostly utilized in research. In the early 1980s, Audiologists developed a fascination with matching real-ear results to prescriptive targets on a computer monitor through equipment that became more widely accessible. Even with greater accessibility to the equipment and the decrease in price for the equipment, it is still underutilized in most clinics. Hearing Aid Dispensers have access to this equipment in about 23% of their practices. Audiologists have access to this equipment in about 73% of their clinics. However, despite having the equipment, only 50% of these individuals routinely use the equipment in their hearing aid fittings. The reason for this discrepancy is reliant on whether the professional was trained how to do the testing and the purpose behind utilizing this in their fittings. Dr. Mendoza has utilized this equipment since the early 1990’s when she obtained her Audiology and Hearing Aid Dispensing license and was trained by the pioneers of probe microphone measurement fittings.
The purpose behind Real Ear Measurement testing is for accuracy of the fitting of the hearing aids that you, as the consumer, purchase. One thing to consider when being fit with hearing aids is: What is the hearing aid actually doing in your ear? You may not realize this when you purchase hearing aids, but just as a fingerprint is unique to each individual, your ear has a unique ear canal resonance that is unique to the size and bending of your ear canal, the length of the ear canal and how wide and how narrow your ear canal is at various points of your ear canal. This very unique resonance is utilized in the fitting of your hearing aids when probe measurement testing is utilized. The test consists of putting a very small probe tube in your ear canal which measures the unique resonance of your ear. Then your individual hearing aid is placed in the ear canal, alongside the probe tube and there is a series of algorithms that add and subtract decibels at very specific frequencies to exactly match your unique hearing prescription. This is completed through a very complicated computer and with adjustments in the hearing aid fitting by the Audiologist. This is further filtered and adjusted for noise reduction, directionality and fitting formula that is used for your unique needs. If you are fit with hearing aids and there is no probe measurement fitting being completed, it is like wearing a wedding gown right off the rack with no seamstress to fit the dress to your particular body style and frame. The dress will have gaps in some areas, be too tight in other areas and overall not look as stylish and beautiful as a dress that has been altered for you. A hearing aid that is not precisely fit to your hearing loss, ear canal resonance and personal fitting preferences is incomplete in its final adjustment and will never be able to function as well as hearing aids that go through the Probe Microphone, Real Ear Measurement fitting process.
Real Ear Measurement is 100% necessary with every hearing aid fitting. Not only should the Real Ear Measurement be completed at the delivery of the hearing aids, but on an annual basis to make sure the aids are working well for your audiological needs and also in the case of a decrease in your hearing. Real Ear Measurement testing is something that makes sure the aids are aligned exactly with your hearing loss. Imagine if you went and had your tires rotated on your car and they never balanced the tire to make sure it was on the rim accurately. If they were not balanced, the end result is a wearing away of the tire that is not accurate because the tire was never balanced. The same result happens with hearing aids. If they are not evaluated for the fit, sound quality, verification of hearing aid features like directionality and compression technology, there is no way to know if the hearing aid is fit to your ear as accurately as it could be when this technology is used.
Real Ear Measurement can be just a single insertion gain curve where the Audiologist will measure one particular input level to see if the aid is meeting the target gain for that specific input level. Speech mapping is like a single gain curve on steroids. It looks at the dynamic gain of the hearing aid for soft, average and loud sounds at one time. It makes sure the hearing aids are giving enough gain for soft sounds and average sounds. It is also making sure the hearing aid is not exceeding your uncomfortable loudness level (UCL) where you can no longer tolerate volume with the hearing aid with louder inputs. Hearing aids have compression technology wherein the hearing aid will compress sound that exceeds your UCL. In the past, hearing aids would have something called peak clipping where the loudest output of the hearing aids was clipped off, which created distortion. The newer hearing aids all have compression technology where this does not happen. Speech mapping allows for a very precise fit of the hearing aids to the user, without going too loud and making sure it is also providing enough gain for soft sounds.
The test consists of putting a very small probe tube in your ear canal which measures the unique resonance of your ear. Then your individual hearing aid is placed in the ear canal, alongside the probe tube and there is a series of algorithms that add and subtract decibels at very specific frequencies to exactly match your unique hearing prescription. This is completed through a very complicated computer and with adjustments in the hearing aid fitting by the Audiologist. This is further filtered and adjusted for noise reduction, directionality and fitting formula that is used for your unique needs.
Calibration of the Probe Microphone is a process that happens before you ever enter into the office for the fitting of your hearing aids. The calibration process is there to make sure the room environment is quiet enough to perform the testing and to make sure the speaker from where the sound is emulated is equalized to the microphone on the probe testing unit. If there is any discrepancy with the calibration, the computer will self adjust the microphone to be calibrated prior to you sitting down for the testing procedure.
REAG (Real-Ear Aided Gain): This refers to the difference in decibels between the SPL as a function of frequency at a specified measurement point in the ear canal and the SPL at the field reference point, for a specified sound field, with the hearing aid (and it's acoustic coupling) in place and “turned on.” This relates to the probe tube being in your ear canal, with no hearing aid, and measuring the ear canal resonance of your unique ear.
REOG (Real-Ear Occluded Gain): Difference in decibels between the SPL as a function of frequency at a specified measurement point in the ear canal and the SPL at the field reference point, for a specified sound field, with the hearing aid (and it's acoustic coupling) in place and “turned off.” This relates to putting the hearing aid in your ear, in an off position, with the probe tube alongside the hearing aid to measure what happens to the ear canal resonance of your ear with an object in the way of the sound entering your ear canal.
REIG (Real Ear Insertion Gain): Difference in decibels, as a function of frequency, between the REAG and the REUG, taken with the same measurement point and the same sound field conditions. This is when the probe tube is in your ear canal, the hearing aid is turned on, and the difference between the measurement with no hearing aid in the ear and the hearing aid in your ear and turned on, is revealed in a gain curve. It is the way for the Audiologist to determine if you are getting the right amount of amplification for soft, average and loud sounds.
Probe Tube Measurement, Real Ear Measurement, Real Ear and Aided Testing are all synonymous terminologies that signify that your hearing aid is fit 100% accurately to your hearing loss.
At Optimum Audiology, we know that fitting your hearing aid accurately is the best way to verify the hearing aid integrity, to provide the best opportunity for fitting success with the hearing aid and to maximize the hearing aid technology for your hearing loss. If this vital step is missed, it is quite likely your hearing aid is not fit specific for your hearing needs. In addition, any faults that the hearing aid may have will not be known, as they were not tested. Dr. Mendoza has been a long time proponent of this type of system and follows “Best Practices” for hearing aid fittings. She belongs to the Dr. Cliff Best Practice Pro network of providers. This network verifies that all those belonging to the network have up to date calibration of all their equipment, use the latest hearing aid technology, and perform Real Ear Measurement at all deliveries and at yearly intervals.
