Tech Topic | April 2016 Hearing Review
Results and implications of a field-trial study about how a new advanced hearing aid improves the overall real-life satisfaction in various listening situations over the wearers’ own hearing aids.
In a previous paper, we reported on the design rationale of the UNIQUE hearing aid and the key features supporting the design.1 Briefly, the UNIQUE hearing aid is designed so wearers spend the least amount of listening effort across listening situations and are still ensured optimal performance. This is judged important because recent work from cognitive sciences suggests that people with different cognitive capabilities may respond differently to the signal processing of a hearing aid.2 By designing the hearing aid to require the least listening effort from the wearers in more situations, it is hoped that people with good and not-so-good cognitive capacities can all receive maximum benefits from the hearing aids commensurate with their potentials. This article summarizes the results of a field-trial study on how such a hearing aid improves the overall real-life satisfaction in various listening situations over the wearers’ own hearing aids.
New Features for Effortless Hearing
Effortless hearing is based on the premise that the hearing aid captures as much of the natural input as possible, “cleansing” it so only the relevant sounds are processed in order that all sounds are consistently audible, comfortable, and intelligible. To capture all the natural nuances of the environments, the UNIQUE uses True Input Technology with an 18-bit analog-to-digital converter (ADC), yielding an upper input limit of 113 dB SPL and an input dynamic range of 108 dB. In addition, it uses a sampling frequency of 33 kHz, yielding an input bandwidth of 16.5 kHz. The system uses 4 ADC (one for the front microphone, one for the back microphone, the remaining 2 for other purposes such as T-coil). These features ensure that the UNIQUE captures the widest range (intensities and frequencies) of sounds consistently. The expected benefit is the potential for improved sound quality and naturalness of all input sounds.
To purify the incoming sounds, the UNIQUE introduces a patented Wind Noise Attenuation algorithm that provides over 8 dB signal-to-wind noise ratio (SNR) improvement.3 This makes speech understanding in moderately windy situations possible. A new Soft Level Noise Reduction algorithm is available so soft level noises are not audible while soft level speech remains audible. This ensures audibility while minimizing extraneous noises. A multichannel fully adaptive directional microphone takes advantages of the spatial separation between speech and noise sources to further improve the SNR of the input reaching the hearing aid for processing. The Real-Time Speech Enhancer takes advantage of the spectral difference between speech and noise to improve listening comfort in noisy backgrounds. Overall, the expected benefit of this purification is improved ease of speech understanding in difficult listening situations such as wind noise and other noisy places (including large groups, parties, etc).
The most crucial element in a system designed under the effortless hearing rationale is how the system ensures consistent audibility in as many listening situations as possible with minimal wearer requirements, both cognitively and physically. This is because different listening environments require a different set of electroacoustic settings for optimal performance.4 It would be the least effortful for the wearers if the hearing aids automatically switch to the most optimal settings in all environments, each using a set of optimal sound processing algorithms.
In the UNIQUE, this is achieved using a Variable Speed Compressor (VSC) and the Sound Class Technology (SCT) system. The VSC uses both fast and slow acting compression to ensure the integrity of the temporal waveform while enhancing audibility of soft and loud sounds. This could benefit individuals with good and poor cognitive potentials. (A future article will address this feature and its benefits in more detail.)
The new SCT system is designed to ensure seamless integration of all features. The system has two components: a classifier and a controller. In the classifier, the input signal is analyzed on 12 attributes (eg, envelope modulation, amplitude modulation, etc). The input signal is then classified as belonging to 1 of 9 different sound classes. They include 5 where speech is absent: 1) quiet; 2) urban noise; 3) transportation noise; 4) party noise, and 5) music. The other 4 classifications involve situations where speech is present: 6) quiet with speech; 7) urban with speech; 8) party with speech, and 9) transport with speech. Once a decision is made on a sound class, the range of parameter settings from the previous sound class is updated automatically to optimize the settings for the new environment, via the controller of the SCT. This could include the amount of impulse sound reduction (TruSound Softener), the amount of Soft Level Noise Reduction, the speed of the RT Speech Enhancer, etc.
The system is therefore designed to automatically respond to all listening situations with the most optimal set of parametric settings without wearer effort or awareness. The parameters involved in optimizing to a specific listening situation are illustrated in Figure 1. An expected benefit of this processing is more consistent speech understanding and listening comfort in all listening environments without additional wearer effort.
The features described earlier under the effortless hearing rationale hold promise for the UNIQUE to meet the listening needs of more wearers, and make their hearing aid experience more satisfactory than their own hearing aids using current technologies. During our pilot laboratory tests of each individual feature, wearers reported better sound quality, more consistent speech intelligibility across situations, and more comfort listening with the UNIQUE hearing aids than their current hearing aids. In order to verify that these benefits are realized in the real-world use of the UNIQUE, we conducted a multinational, multi-center study comparing wearer satisfaction in various listening backgrounds between the UNIQUE hearing aid and the wearers’ own hearing aids.
The study was conducted at the launch of the UNIQUE hearing aids. Hearing care professionals (HCP) from the United States, Canada, and France participated. In all, there were 11 sites in the US, 6 sites in Canada, and 9 sites in France that participated (see Acknowledgements). The test sites were not compensated for their participation. Each test site recruited its own clients as subjects. Some recruited their most difficult clients, some recruited clients on their waiting list for the newest technology, while others included clients who were seen during the data collection period who met the inclusion criteria. These clients were informed that, as part of the study, they would have to complete satisfaction questionnaires on their own hearing aids and the study hearing aids. They were allowed to withdraw from the study at any time. Subjects were given a discount on the price of the UNIQUE hearing aids only after they decided to purchase the UNIQUE aids at the end of the study. Test subjects were assigned a study ID by the participating HCP. Only the HCP knew the identity of the study participants to protect their privacy.
Subjects included in the study were adult hearing aid wearers (>18 years of age) who had worn hearing aids for at least year. Their current (or own) hearing aids included all recent makes and models from the major hearing aid manufacturers including Widex. They had various hearing loss configurations in the mild to moderately severe hearing loss categories. All the hearing losses were within the fitting range of the UNIQUE 440 Fusion hearing aid. There were no literacy or cognitive requirements on the subjects other than their ability to read and complete the study questionnaire. In all, there were a total of 101 subjects who participated in the survey. A total of 53 test subjects (52% of the total number) were from the US, 30 (30%) from Canada, and 18 (18%) from France. Sixty-nine (69) were male and 32 were female. The average age of the participants was 70.5 years (SD=10.8 years). Slightly more than half (56%) of them were retired, while 44% were actively working. All participants were fitted with the UNIQUE 440 Fusion receiver-in-the-canal (RIC) hearing aids using either an M- (moderate power) or P- (power) receiver connected via EasyWear earwire5 to instant eartips. Custom earmolds were used for current Widex wearers if they had such earmolds prior to the study.
A standard fitting protocol was provided to all participating HCPs. Briefly, the fitting protocol specified the rules for selecting various eartips and receivers. It outlined the fitting procedure, which included performing the Feedback Test and measuring the Sensogram. The default Widex fitting prescription target was used along with the default feature settings. While the HCPs were instructed to use the default settings of the UNIQUE hearing aid as their first attempt, they were allowed to make fine-tuning adjustments if necessary. Test subjects who reported tinnitus were recommended the use of Zen tones and the Widex Zen Therapy protocol6 as part of their tinnitus management. An optional verification protocol using the SoundTracker7 and Ling6 sounds, as well as an orientation checklist were recommended.
The main tool used in the study was a custom questionnaire that was based on the questions used in the MarkeTrak studies.8,9 Questions included satisfaction ratings on a number of key hearing aid features and listening situations. Additional questions, such as the use of the hearing aids in wind noise and listening to music, were added. Most ratings were based on a 7-point scale, with “1” being “very dissatisfied,” “7” being “very satisfied,” and “4” being “neutral.” Items on each subscale are listed in Table 1 along with the summary statistics (see the online version of this article for more responses to questionnaire items). All questionnaires were completed on paper by the subjects, collected by the HCPs, and mailed to ORCA-USA for analysis. Questionnaires were entered by a third party data-entry personnel twice—once into an Excel spreadsheet, and once into the ORCA website where an online version of the questionnaire was available. Entries from both sources were reconciled to minimize errors prior to final data reduction and analysis.
The median responses on each item for the subjects’ own hearing aids and the UNIQUE hearing aid are provided in Table 1. In addition, the ratings at the lowest 10% (10th percentile) and the highest 10% (90th percentile) are also shown. These indices provide an estimate on the ratings of the poorest performing subjects, average subjects (median or 50%), and best performing subjects (highest 10%-tile or 90%). A Wilcoxon Signed Rank test was conducted to compare the ratings between the subjects’ own aids and the UNIQUE aid on each item. Items that show a significant improvement with the UNIQUE aid are indicated with an asterisk (*). It should be noted that a lack of difference in median ratings does not imply statistical insignificance (see highlighted items) and vice versa. Unanswered items, or items that have responses indicated as “not sure” or “not available” were excluded in the summary.
Overall satisfaction. Table 1 shows that the median hearing aid satisfaction rating is “5” (or “somewhat satisfied”) for subjects’ own hearing aids but “6” (or “satisfied”) for the UNIQUE hearing aid. This suggests that the UNIQUE hearing aid is more satisfactory than the subjects’ own hearing aids. On the other hand, the rating for the lowest 10th percentile is “2” (or “dissatisfied”) for the subjects’ own aid and “4” (or “neutral”) for the UNIQUE aid. This suggests that over 90% of the hearing aid wearers find the UNIQUE to be at least “neutral” or “satisfactory.” The fact that the highest 10% (or 90th percentile) is “6” (or “satisfied”) for the subjects’ own aid and “7” (or “very satisfied”) with the UNIQUE aid suggests that one can expect over 10% of the wearers will find the UNIQUE as “very satisfactory,” but less than 10% of the wearers will find their own aids as “very satisfactory.”
The subjects’ responses on the various sections of the study questionnaire may provide insights into which aspects of hearing aid use affect overall satisfaction ratings. Sections with items that showed a higher satisfaction rating with the UNIQUE aid over the subjects’ own aids are likely contributors to the enhanced satisfaction. Sections with items that showed similar ratings between the subjects’ own aids and the UNIQUE aid are unlikely contributors to enhanced satisfaction. However, they support the contention that the UNIQUE ensures equal satisfaction on the said categories.
Likely Contributors to Enhanced Satisfaction
Expectations. Table 1 shows that subjects rated their own hearing aids as meeting their expectations (“4” or “about as expected”). However, they rated the UNIQUE aid “5.5” or “better than expected.” It is reasonable to expect that devices that exceed one’s expectations are more satisfactory.
Overall sound quality. In general, subjects’ own hearing aids were rated “5” or “somewhat satisfied” and the UNIQUE aid was rated “6” or “satisfied” in all items under the sound quality subscale. The only exception was the “ability to hear soft sounds” where the own aids were rated “neutral” or “4” and the UNIQUE aid was rated “satisfied” or “6.” This supports the long established contention that a Widex hearing aid provides better audibility for soft sounds because of its low compression threshold.11 In addition, it also supports the effectiveness of new features in the UNIQUE hearing aid. This includes the Soft Level Noise Reduction, which provides more audibility for soft speech sounds without increasing the audibility of soft noises. The High Frequency Boost feature increases the gain for soft- and medium-level sounds from 6,000 to 8,000 Hz while decreasing its gain at a higher input level (Figure 2).
Effectiveness of enhanced features. Subjects rated the UNIQUE hearing aid as one interval higher than their own hearing aids on all items. Even though the median rating on “ability to tell sound direction” was the same for the own aids and the UNIQUE aid, the UNIQUE aid was significantly better than the own aid (z = 3.96, p < 0.05). This supports the efficacy of the UNIQUE features, such as Inter-ear compression for localization and distance, Feedback Cancellation (whistling), RT Speech Enhancer, HD Locator directional microphone for noisy backgrounds, and Zen for tinnitus or relaxation purposes (Figure 3).
Use in multiple listening environments. Figure 4 shows the UNIQUE aid was rated one interval higher than the own aids in almost all environments, from a rating of “5” (somewhat satisfied) to “6” (satisfied). Even though the median rating for “conversation with one person” was the same for both own aids and the UNIQUE aid, the rating on the UNIQUE aid was statistically better than own aids. Items that showed differences greater than 2 intervals included: “talking to children,” “at a large hall,” “in a restaurant,” “outdoors on a windy day,” and “walking or running outdoors.”
This supports the efficacy of the various sound purification features such as the Wind Noise Attenuation algorithm, the RT Speech Enhancer, the HD Locator and signal processing features including the Variable Speed Compression, and the Sound Class Technology system. The latter may be especially instrumental in seamlessly integrating all the algorithmic settings across situations without additional wearer effort.
Ensuring satisfaction on ergonomics: Physical comfort/fit overall. Subjects’ own aids and the UNIQUE aids were both rated as “6” or “satisfactory” in overall comfort/fit, suggesting both aids were satisfactory to the subjects and were similar in comfort, looks, and size. Items that the UNIQUE aid were rated better than the subjects’ own aids included the “appearance” and “visibility” (Figure 5).
Ease of use items. In general, subjects rated the UNIQUE hearing aid just as easy to use as their own hearing aids, with a rating of “6”, or “satisfied” on all the items. The only exception was on “battery life” where a rating of ‘5” was assigned to subjects’ own aid but “6” to the UNIQUE aid. Interestingly, even though items like “Ease of use overall,” “amount of effort for maintenance,” “ease of cleaning/care” had the same median ratings, the UNIQUE aid was rated significantly higher than the subjects’ own aids (Figure 6).
Attitudes/beliefs. Figure 7 shows that all items other than “mental ability” were given a rating of “5” (somewhat satisfied) or “6” (satisfied) for both the subjects’ own hearing aids and the UNIQUE hearing aid.
A Wilcoxon Signed Rank test showed that these ratings were significantly higher than the neutral rating of “4.” This supports the assertion that hearing aids improve relationships, social interaction, sense of self, and quality of life, in addition to communication abilities. Despite the higher median ratings assigned to the UNIQUE aids on many items (eg, “relationships at home,” “social life,” “sense of independence”), the difference between the own aids and the UNIQUE aid was not statistically significant.
These relatively high satisfaction ratings suggest that subjects were satisfied wearers of their own hearing aids before the study. The similarity in median ratings between the UNIQUE and the own aids on these categories shows that the UNIQUE hearing aid is viewed as favorably as the subjects’ own hearing aids; the UNIQUE design rationale achieves the functionality improvements while ensuring ergonomics performance.
A linear regression analysis was conducted to examine the factors that may affect overall satisfaction. The ratings on the item “overall satisfaction” were used as the dependent variable, and all items within the custom questionnaire were used as the independent variables.
The following equation explains 62% of the variance (R2 = 0.62, p < 0.001):
“Overall Satisfaction” = 0.285
+ 0.522 x “Overall All Listening Situations”
+ 0.209 x “Overall Sound Quality”
+ 0.233 x “Expectations”
That is, the overall satisfaction for a hearing aid largely depends on how well it functions in different listening environments (most weight), followed by its overall sound quality and the wearers’ expectations for the hearing aids. The other variables also contribute, but minimally.
Hearing aids differ by how well they handle the individual wearer’s listening needs across listening situations. Indeed, Kochkin10 indicated hearing aids that yield satisfactory performance across more listening situations are likely more satisfactory than those that yield satisfaction in limited situations.
A challenge for hearing aid designers is to achieve satisfaction across many listening situations (eg, good sound quality and intelligibility in soft and loud, and quiet and noisy environments) and still be commercially acceptable. The additional commercial requirements include: easy to use, minimal wearer adjustment, acceptable appearance, and a low current drain on the battery. While these may not be the major determining factors in the overall satisfaction for a hearing aid, inadequacy in any of these areas increases resistance to the use of hearing aids.
This feat of meeting all objectives without compromises may only be achieved with a design rationale that not only considers the engineering aspects of good sound processing, but also human aspects in order for people with good and not-so-good cognitive potentials to benefit. The observations that the UNIQUE hearing aids are rated higher than the test subjects’ own hearing aids across all listening situations, and yet similarly on ergonomics, is a testament to the success of its design.
It is noteworthy to review those features that may be responsible for the situations where the UNIQUE was rated more than one interval higher than the subjects’ own aids. This includes “soft sounds,” “children,” “restaurants,” “windy outdoors,” “walking/running outdoors,” and “large lecture rooms.” The ability to hear “soft sounds” and “children” better is likely related to the low compression threshold that is used in all Widex aids. In the UNIQUE, this is enhanced with the Soft Level Noise Reduction algorithm and the High Frequency Boost feature. The former distinguishes between soft speech and soft noise so only soft speech is amplified. The latter provides additional amplification to low and medium sounds in the high frequency region so better intelligibility can be expected.
An additional feature that provides consistent audibility to soft speech is the Variable Speed Compressor. This algorithm preserves the temporal structures of the input sounds while maintaining consistent audibility even with large changes in the input intensities (ie, from loud to soft, and vice versa). Consistent audibility and natural temporal structures are important for all listeners, but especially those with poor cognition.
The ability to function better in “restaurants” and “large lecture halls” would likely owe its credit to the real-time Speech Enhancer and the HD Locator. The former is a combination of noise reduction and speech enhancement features that automatically adjusts the frequency-gain settings on the hearing aid in order to maximize the speech intelligibility index (SII) for the wearer in the specific listening environment.12 In the UNIQUE, this algorithm is further enhanced to be more responsive to changing noise backgrounds. The HD Locator is a multichannel fully adaptive directional microphone also enhanced with increased responsiveness.
In addition to these proven features,13 the UNIQUE implemented the Sound Class Technology system that detects the identity of each listening environment to further augment and coordinate the actions of each individual feature for all listening environments. The result is an ever-changing set of hearing aid parameters optimized to provide the best available signal-to-noise ratio of the input sounds for speech understanding.
The Wind Noise Attenuation algorithm is undoubtedly the main reason for the improved satisfaction in the “windy outdoors” and “walking/running outdoors” situations. This patented algorithm has shown over 8 dB improvement in speech-in-wind performance in the laboratory.3 The unique algorithm extends the effective use of hearing aids from just the indoors to both indoors and outdoors.
The results of the field trial study confirmed the many observations we have made on the UNIQUE during laboratory studies of each individual feature. That is, the new device has abundant features that improve the consistent audibility and intelligibility of speech sounds. We have proven in this field study that such benefits are reflected in real-world listening situations, leading to an overall improved wearer’s satisfaction for hearing aids.
We appreciate the great efforts by the clinicians and test subjects at the following sites for helping in the data collection process. Sites in Canada included: Audiology Clinic of North Alberta, Beaudry Roy Audioprothesistes, Davidson Hearing Aid Centre, Grand River Hearing Centre Inc, Marco Hearing Health Centre, and North Bay Audiology Clinic. Sites in France included: Amplifon Sartrouville code 296, Audio Plus, Audition Conseil, Audition Donibane, Audition Langlet, Centre Auditif Nicolas Gode, Eurl Audition Jezequel, Pavillon de L’Audition Sarl, and Plaisir Entendre. Sites in the US included: Associated Audiologists, Audiological Consultants of Atlanta, El Dorado Audiology, ENT Associates of Johnstown, ENT Associates of South Florida, HearCare Audiology, Hearing Associates, Madison Hearing, Pacific Hearing Service, Shohet Ear Associates, and Today’s Hearing.
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Francis Kuk, PhD, is director, Chi Lau, PhD, is a researcher, and Eric Seper, AuD, is a research audiologist at the Widex Office of Research in Clinical Amplification (ORCA) in Lisle, Ill. Marianne Sonne, MA, is an audiological affairs specialist at Widex A/S in Lynge, Denmark. Correspondence can be addressed to Hearing Review or Dr Kuk at: [email protected].
Original citation for this article: Kuk F, Lau C, Seper E, Sonne M. Real-life Satisfaction with a Hearing Aid Designed to Enhance Effortless Listening. Hearing Review. 2016;23(4):40.?