New Computer-aided Measurement System for Hearing Aid Fitting

Managing a successful hearing care practice requires that the dispensing professional must maintain their professional credentials, while displaying uncommon business acumen and technical expertise. Many audiologists and hearing instrument specialists try to build their businesses by focusing their resources on acquiring new patients. However, business owners would do well to look to their current patient base as a resource for new customers, because these satisfied customers are the ones who—as a result of their positive experiences—will demand less customer service and share their experiences with their friends.

So the key question becomes “How do I ensure that my customers are satisfied?” Hearing care professionals know that satisfaction ultimately comes as a result of proper fitting procedures, which, in turn, are based on using increasingly advanced technologies that are easy to use and that improve the patient counseling experience. This is where technical expertise melds with the clinician’s ability to translate professional knowledge and recommendations to the patient.

Acousticon, a well-established German company whose products are now being introduced to the United States, has developed an advanced hearing aid fitting system that helps hearing care professionals objectively determine not only which hearing aid is best for the patient over the longer term, but also how to fit those hearing aids so the patient can understand speech in nearly all listening environments and enjoy all their favorite music again.

Acousticon was founded in 1984 by audiologist Harald Bonsel. Three years later, in 1987, the company began focusing primarily on development of its audiological measurement technology, called ACAM (Acousticon Computer-Aided Measurement). The technology has seen improvements through the decades and is now in its fifth generation.

ACAM 5 (Figure 1), an integrated software and hardware system, is designed to help the hearing care professional optimize the patient’s ability to hear in all ambient noise conditions. It does this through automation of percentile analysis and other advanced measurements and fitting processes. The modular design of the system gives the user control over which components he or she desires to use and makes it possible to use the entire system with all hearing aids made by any manufacturer.

Percentile Analysis Benefits

Percentile analysis is a method that up until now was used primarily in hearing aid research and development. Acousticon succeeded in integrating this method into its ACAM 5 audiological measurement technology. Thus, for the first time, percentile analysis is available for fitting individual hearing aid systems in a way that is consistent with the draft international standards (IEC 118-15).

Percentile analysis supplies concrete and significant information regarding the acoustical properties of particular digital hearing aid systems. Certain settings, which earlier could be achieved only on the basis of experience or by trial and error, can now be optimized quickly, easily, and reliably with the help of detailed analyses. This especially holds true for the improvement of speech recognition with background noise.

Percentile analysis also allows the hearing care professional to analyze real speech, music, or any sound—as well as the output of the hearing device over every frequency and loudness level relevant to hearing—not just the mean frequency or mean loudness. This provision enhances the ability to set target gains in an objective data-driven way and to avoid repeat visits from less-than-satisfied customers.

Experience shows that, with this method, the signal-to-noise-ratio (SNR) can be raised in some cases by up to 4 dB compared to the conventional first-fit setting of the hearing aid system. Initial studies conducted by Acousticon suggest that, in almost 80% of all cases for which percentile analysis was used (along with REM and the other tools in ACAM), patients reported a perceptible hearing improvement—even when the hearing aid had already been properly fitted according to conventional fitting methods.

LTAS, LTASS, and Percentile Analysis

Percentile analysis is an extension of LTAS (Long Term Average Spectrum) measurements, which have been used for years in the hearing industry to measure sound signals. However, because speech consists of many dynamics over a wide frequency range, some manufacturers have extended LTAS to LTASS (Long Term Average Speech Spectrum) to give clinicians another tool for understanding the dynamics of speech and other more complex sounds, such as music. LTASS averages every frequency band over time—a useful tool for dispensing professionals who want to analyze speech.

As an alternative, some manufacturers (including Acousticon) have developed LTAS into a tool called percentile analysis. This can be useful to a clinician who wants to analyze all the frequency bands and dynamics of speech where there are many more dynamics than one finds in simulate speech (eg, speech noise). Percentile analysis, which is a statistical algorithm, summarizes measurements of all frequency bands and dynamics over user-defined time periods. Therefore, it can be a useful tool for optimizing a hearing aid and providing a patient with a wider range of everyday speech dynamics.

Percentile analysis of speech-simulating noise is identical to the LTAS measurement; it is simply the application of percentile analysis in real-speech and the display of all the dynamics that might be useful when fitting a hearing aid. For example, the data can be used to adjust a hearing aid so it delivers softer sounds throughout the frequency spectrum. Or, as another example, the information can be used to determine which frequencies should be amplified to meet the patient’s hearing preferences over the life of the hearing aid.

To illustrate the differences and similarities between LTASS and percentile analysis, Figures 2 and 3 show the percentile analysis and the LTASS value of two different signals: a standard noise signal (Figure 2) and a speech signal (Figure 3). The percentiles (bars) show the dynamic loudness range of the signal in dBSPL. The blue bars show the dB levels ranging between 30% and 65% of the signal level, and the red line shows the average LTASS dB level (which is comparable to a 65 percentile level). The red bars show the 65% to 99% dB range of the signal level.

Note that, in Figure 2, the percentile bars are small, which tells the clinician that the sound has minimal (low) dynamics. In contrast, the bars in Figure 3 are much larger, demonstrating that speech has many dynamics and a much higher range of sound levels for each frequency band.

Hearing care professionals can use percentile analysis, in addition to other analytical tools and their own judgment, to create a target gain curve for the hearing aid. Depending on each patient’s personal preferences, the ACAM 5 system allows the dispensing professional to use the percentile-fitting tool and/or other methods (eg, NAL or DSL) to establish the personalized fitting.

So, How Do I Use Percentile Analysis in the Fitting Process?

The ACAM 5 fitting process and its built-in audiology tools work together to optimize the performance of any hearing aid for virtually all patients. Unlike some fitting processes that seek only to make the patient “hear” immediately upon purchase of a hearing device, the ACAM 5 process is designed to meet all the patient’s hearing goals over a lifetime.

The fitting protocol, which takes a total of 15 to 30 minutes, is:

1. Calculate percentile analysis to arrive at the “target gain” curve (that is, the amount of gain the hearing device should give to the output signal across the entire frequency spectrum common to normal speech);
2. Conduct real-ear measurement; and
3. Determine the patient’s loudness perception with loudness scaling.

Fitting a hearing aid with the ACAM 5 system starts with the use of the built-in audiometer. As with most other audiometers, it uses puretones to measure the patient’s hearing loss and chart the threshold hearing levels, as well as the uncomfortable loudness level (UCL). However, the ACAM 5 system also allows the user to automatically retrieve archived audiograms, compare them to the patient’s most recent audiogram on the instrument’s computer monitor, interface with the manufacturer’s fitting software, measure and validate the performance characteristics of any hearing aid, make necessary compensations, and use those findings to fit the hearing aid to the patient’s specific hearing loss and hearing needs.

Then, to take advantage of all of the features of the ACAM 5 system, the recommended procedure is to use the built-in real-ear measurement (REM), the hearing instrument test (HIT), and the built-in software to fully understand and validate all of the performance specifications of the individual hearing aid being fitted. The ACAM 5 system combines ISTS with other integrated sound signals in the HIT box. The output of the hearing device from within the box is automatically reflected in the ACAM 5 software, making it possible for the clinician to accurately analyze the output.

The components of the system provide the information needed to help optimize the frequency shaping with the use of the sliders provided in the fitting software, and to ensure the hearing aid has enough reserve gain that it can still serve the customer even after a number of years of continued hearing loss. The ACAM 5 system has all the tools necessary to make sure the patient doesn’t experience sounds that are uncomfortable, and to hear all audible sounds of everyday life—especially speech—in all listening environments. Further, it allows accurate and objective determination of the most comfortable level (MCL), threshold, and UCL, so residual hearing can be maximized, allowing the user to overcome any challenges posed by the hearing device at specific frequencies.

The ACAM 5 system also includes Loudness Scaling to assist the hearing professional in analyzing the patient’s psychological and physiological responses to sounds (psychoacoustics) and in using this information to more accurately calculate the target gains he or she wants to apply. In addition, there is a program designed to assist the dispensing professional in retraining the portion of the patient’s brain that may have lost some of its auditory sensing capabilities.

New technologies continue to provide new methods for delivering hearing care while also providing new revenue opportunities. The ACAM 5 measurement system is a system that combines long-established acoustic principles in a new way to assist the dispensing professional to achieve an exceptional level of fitting success for all patients and all hearing aid systems.