New Studies Show Limitations, Potential Benefits of PSAPs

December 7, 2018

Two recently published studies from independent hearing aid research labs indicate that some personal sound amplification devices or PSAPs could offer benefit to individuals with milder hearing loss.

The first study, published on-line in September in the American Journal of Audiology, was conducted by researchers at the University of Iowa. In the laboratory-based study, they compared the performance of three PSAPs to one conventional hearing aid in 25 older adults with bilateral mild to moderate hearing loss.

All devices were fitted bilaterally. The conventional hearing aid was fitted by an audiologist using prescriptive methods and real-ear verification techniques. The hearing aids were configured with two listening programs, one for quiet (omni-directional microphone + noise reduction off) and the other for noisy listening places (directional microphone + noise reduction on). The PSAPs were fitted with default earpieces and two pre-set programs, one for quiet and the other for noisy listening situations. The users were able to adjust the volume of all devices to their preferred setting prior to the completion of any testing.

A series of speech recognition and listening effort tests, as well as sound quality judgments were obtained from the listeners. Testing was completed in the unaided condition, followed by aided testing using the four devices. Although testing was completed in the soundbooth, the speakers were configured to mimic real-world listening places. Six listening situations were arranged using the 8-speaker array by varying the intensity and direction of the speech and noise and use of visual cues. Listeners were also asked to rate listening effort and sound quality on a Likert scale.

All devices improved speech recognition and listening effort compared to the unaided condition. As expected, the hearing aid provided more audibility than the PSAPs, thus aided speech intelligibility scores were higher for hearing aid compared to the three PSAPs.

Since all three PSAPs provided some speech intelligibility and listening effort improvements relative to the unaided condition and given the $300 to $400 retail price point of the PSAPs used in this study, the authors conclude that the PSAPs used in this study could serve as a budget-friendly alternative to conventional hearing aids for adults with mild to moderate hearing loss.

The second study, published in the November issue of Hearing Review, was conducted in the lab at Washington University in St. Louis. The main objective of this study was to compare 2 cc coupler and real-ear performance data for a collection of various PSAPs compared to the gold standard performance of four conventional hearing aids (two with advanced technology and two with basic technology).

Table 1 below from the study shows all the devices evaluated. Unlike other published studies that have investigated the performance of PSAPs, the researchers divided the PSAPs into three categories, dependent on their features. The researchers evaluated the performance in both the coupler and a “dummy ear” of all devices for eight different audiometric configurations, ranging from very mild to mild sloping to severe.

Table 1. Devices and their associated features, from Voss et al Hearing Review Nov 2018

According to the authors, for 2cc coupler measures “almost all” devices matched their manufacturer’s specification requirements. For the real-ear measures, both “first-fit” and “programmed” responses were obtained. The authors used a “percent of the time” criteria that they defined as matching the NAL-NL2 prescriptive target +/- 5 dB for soft and average inputs for each of the eight audiograms. Following both the “first-fit” and “programmed” measures, results of each device was placed into one of three categories:

  1. Matched target 88 to 100% of the time
  2. Matched target 75 to 87% of the time
  3. Matched target less than 75% of the time

The “percent of time” calculation was determined by dividing the total number of targets by 18 total number of targets (nine values each for soft and average inputs levels from 250 to 8000Hz).

Results indicated both the advanced and basic hearing aids could be adjusted to match a prescribed target nearly 100% of the time, and just a few of the PSAPs were able to match a target approaching that degree of accuracy. A handful of PSAPs could be adjusted to match the prescribed audibility target for some of the mild hearing losses, and for losses worse than mild all PSAPs provided insufficient audibility.

Interestingly, none of the four conventional hearing aids used in the study provided a close match of the NAL-NL2 targets in their “first-fit” mode, which underscores the key role of a professional adjusting the amplification device to optimize audibility for the individual. In addition, to their thought-provoking findings, the Hearing Review article also provides a very descriptive approach using chickens to educate patients on the role of the licensed professional in the treatment process.

Taken together, both articles demonstrate that properly vetted PSAPs provide a reasonable, lower cost alternative to hearing aids for adults with mild hearing loss. Although any hearing device that performs up to its manufacturer specifications is probably better than using no hearing aids at all, for individuals with more than a mild hearing loss, the PSAPs evaluated in these studies will fall short of audibility requirements needed to improve speech intelligibility.

Finally, a third recently published study might help us better understand the role non-conventional amplification devices, such as PSAPs might play in the clinic.

Titled, What Keeps Older Adults with Hearing Impairment from Adopting Hearing Aids, Maike Tahden and colleagues at Oldenburg University in Germany examined differences in matched groups of hearing aid users compared to non-hearing aid users.Their analysis showed that beyond the traditional hearing test results, non-users perceive their hearing loss to be less severe than their hearing aid user counterparts. Additionally, according to the Oldenburg researchers, non-users exhibited worse technology commitment and lower socioeconomic status relative to hearing aid users.

Given the differences they found in hearing aid non-users, providing alternatives, perhaps through the provision of some of the so-called ‘hydrid’ devices coming to market that do not look like traditional hearing aids, or by delivering different types of counseling that are less dependent on the use of hearing aids – at least initially when a patient is not ready to take-up the use of hearing aids yet – professionals can better serve a wider range of persons with hearing loss.


  1. Certainly good news for the industry, that some measure of audibility is being accomplished with PSAP’s It is well established that mild losses have neuro- transmitter limitations in the cochlea that specifically cause audibility issues first, before further degradation takes place. So PSAP’s are a good start to hearing rehabilitation !
    Good write up!

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