Digital Hearing Aids and Cell Phones: The Impact of New Technology on Phone Use

Study suggests hearing aids have made solid strides—with more to come

An inability to effectively use the telephone has been a major complaint of hearing aid wearers in the past.^1-3 In recent years, telephone and hearing aid technology has advanced considerably. However, there is little systematic knowledge about the impact of these recent advances on telephone usage by hearing aid wearers. This article reports the results of a questionnaire that was administered to understand the impact of modern telephones and modern hearing aids on telephone use.

Telephone Use and Its Challenges

Karrie Recker, AuD, is a research audiologist in the Experimental Audiology group at Starkey Laboratories in Eden Prairie, Minn, and Sridhar Kalluri, PhD, is a research scientist at the Starkey Hearing Research Center in Berkeley, Calif.

Effective communication using telephones is an important component of modern life. It facilitates business and social interactions. Diminished access to this means of communication presumably impairs such interactions. Loss of business and social interactions is known to have an adverse economic impact⁴ and to lower quality of life.⁵ Given the profound impact of telephones on modern life, it is important to better understand how wearers of hearing aids use telephones, and to improve their experiences with these communication tools.

The most recent surveys indicate that approximately 15% to 45% of individuals with hearing loss are unable to use their hearing aids while on the telephone (eg, see Mormer and Mack⁶ and Kepler et al¹). Part of the difficulty is due to reduced audibility and poor speech understanding in noise that results from hearing loss. Telephones exacerbate this situation by reducing the bandwidth of the speech signal and, in the case of digital mobile phones, adding vocoder distortion during its trans­mission. Ad­ditionally, telephone conversations lack the visual in­put that normally assists listeners in noisy situations.

Using a hearing aid in conjunction with a telephone creates additional difficulties. With it comes the challenge of properly coupling a telephone to the hearing aid to obtain the best signal (ie, finding the “sweet spot”). For devices without telecoils, this may be difficult, as feedback (audible oscillation) may occur if the telephone is too close to the hearing aid microphone. For devices with telecoils, it may be challenging to hold the telephone in a specific location to provide good inductive coupling. Additionally, both methods of coupling (acoustic and telecoil) may cause interference with the telephone signal, which may cause a buzzing artifact.^7-14

FIGURE 1. Percentage of individuals wearing analog and digital technology who regularly experienced various problems with telephone use. Significant differences (P <.05) are marked with an asterisk (*).

Study Needs and Rationale

Specific characteristics of the hearing aid, the telephone, and the patient can all affect the telephone experience and thereby influence an individual’s decision to wear a hearing aid during telephone use. Given the considerable changes in both telephone technology and hearing aid technology since the last surveys,^1,2,6 a reassessment of telephone use by hearing aid wearers is warranted. To this end, our survey focused on issues and interactions arising from modern digital hearing aids and modern telephones, particularly cell phones. Additionally, while past surveys have merely reported on the prevalence of specific problems (eg, coupling issues or volume complaints) and the frequency of hearing aid use on the telephone, this study integrates information about individuals’ hearing losses and hearing aids to determine which groups of people are most affected by specific problems and how these problems influence individuals’ decisions to wear their hearing aids during telephone usage. This understanding will guide future hearing aid design solutions for specific patient groups. In order to relate problems encountered during telephone use to specific characteristics of patients and of hearing aids, survey questions were directed along three lines of inquiry.

Style, features, and technology. One line of questioning probed the impact of hearing aid style, hearing aid features, and hearing aid technology. Certain styles of device may be more challenging to couple to a phone than other styles. For example, coupling may be challenging with a BTE device because one cannot simply put the telephone to one’s ear as with custom devices, but must locate the best position at the top or back of the pinna. On the other hand, successful coupling may be challenging for custom devices due to the proximity of the hearing aid microphone to the hearing aid receiver and to the telephone’s receiver (in both cases, the shorter the distance between the two, the greater the likelihood of feedback).

Beyond coupling challenges, device style often dictates whether the hearing aid can accommodate space-consuming features such as volume controls and telecoils, which may help the listener to optimize the sound from the telephone. Despite their potential usefulness, these options may be rejected by individuals who would prefer not to interact with the device by pressing a button, turning a wheel, or searching for the correct spot for telecoil coupling.

Furthermore, the type of hearing aid technology (analog or digital) may affect telephone usage with a hearing aid. A MarkeTrak survey found that wearers of digital devices were 14% more satisfied with telephone usage than were wearers of analog devices.³ This preference is probably due to the presence of adaptive feedback cancellation, a feature that is only possible in hearing aids having digital signal processing.

FIGURE 2. Percentage of individuals who regularly wore their hearing aid during phone use, as a function of hearing aid age. Data were weakly, but significantly, correlated (P <.01).

Cell phones. A second line of questioning examined the impact of cell phones on telephone usage by hearing aid wearers. Kochkin³ noted that satisfaction was typically lower with cell phones than with landlines. This was likely due to the greater amounts of interference experienced by users of cell phones.^8-14 However, satisfaction also may have been lower with cell phones because they were used in more adverse listening situations.

Degree of hearing loss. A final line of inquiry was the relationship between telephone usage and degree of hearing loss. Kochkin³ found that the satisfaction rating for landline telephone use was 17% higher for individuals with mild hearing loss than for individuals with severe hearing loss; for cell phones, the difference was 28%.

A variety of factors could contribute to this finding. In­dividuals with more severe hearing loss will likely want more volume, which they may or may not be able to obtain with their hearing aid/telephone combination, due to gain and feedback limitations. These individuals also typically have greater speech processing deficits, resulting in poorer speech understanding, especially in noise.

In summary, hearing aid wearers face multiple challenges during telephone use. We designed a survey to probe how modern digital hearing aids, modern telephones, and hearing loss interact to shape the telephone experience of hearing aid wearers. Additionally, a major contribution of this study is the effort to connect the specific problems encountered with the decisions of particular patient groups to wear hearing aids during telephone usage.

FIGURE 3. Percentage of individuals who regularly experienced various problems with telephone use, as a function of hearing aid age. Significant correlations are denoted with asterisks (P <.05* and P <.01**, respectively).

Method

To examine the impact of new technology on telephone use, we created a 48-item questionnaire (Appendix A, available in the online version of this article at www.hearingreview.com) asking participants about their hearing aids, their telephone use, and the frequency with which they experienced various problems. Each of the 242 questionnaires mailed included a $1 bill as an incentive for the recipient to complete and return the survey in the postage-paid envelope provided. All individuals wore hearing aids and were active participants in Starkey Laboratory’s research database as residents in the metropolitan areas of Minneapolis and San Francisco.

To focus on the interaction between new hearing aid and phone technologies, we wanted to maximize the percentage of individuals who would answer the questions based on their experiences with their cell phones. Therefore, all individuals who used cell phones for at least 5% of their calls were asked to complete the survey based on their experiences with that phone style. Individuals who did not fall into this category were asked to complete the survey for their home phone, either a corded or a cordless landline. We used the hearing loss and hearing aid information in our database to augment the data analysis; all participants’ records were current to within 2 years.

Because participants completed this questionnaire without supervision, it was impossible to ensure that all individuals responded thoroughly and accurately. Therefore, all graphs include the number of people who responded to a particular question, excluding those who left items blank or replied “not applicable.” Also noteworthy, the terms that were used in the questionnaire were not specifically defined for the participants. Therefore, it is possible that certain problems, such as the interference that is caused during hearing aid/telephone coupling, were classified under more than one category (eg, distortion and/or buzzing), even though the audio and the hearing aid industries recognize this artifact as one of buzzing rather than distortion.

The Spearman Correlation Coefficient was used to quantify the correlation between numeric and ranked variables and the chi-square test of independence to test for a relationship between categorical variables. For ease of readability, the statistical values are reported only in the figures.

FIGURE 4. Percentage of individuals who regularly experienced feedback with telephone use, as a function of device style. A chi-square test performed pair-wise among the hearing aid styles showed that wearers of ITCs and ITEs had significantly more feedback than wearers of BTEs (P <.05* and P< .01**, respectively).

Results and Discussion

Response rate/demographics. A similar percentage of individuals responded from the two sites: 77% from California and 78% from Minnesota. Almost 80% of respondents had digital devices; the remaining individuals either had analog devices or did not know whether their devices were digital. The largest proportion of respondents wore Starkey devices (42%), and the remaining individuals wore devices from other manufacturers or the manufacturer was unknown. BTEs were worn by 37% of individuals, ITEs by 18%, ITCs by 16%, and CICs by 23%. Only a few individuals wore open-fit devices (6%). In all, 62% of individuals completed the survey for their cell phone and 38% for their home phone.

Analog versus digital hearing aids. Of the 159 respondents who knew whether they had analog or digital hearing aids, only 20 reported having analog technology. These individuals were much less likely to wear their hearing aids while on the telephone than wearers of digital devices (25% versus 65%). They also reported more feedback, distortion, buzzing, and inappropriate volume, although most of these differences were not statistically significant (Figure 1).

As most people had digital devices, and we expect this percentage to continue to grow, the remainder of this article will focus on these individuals. At this point, it is important to remember that early digital devices merely implemented analog techniques digitally. Newer digital devices have better algorithms and features, which should improve the hearing aid wearer’s experience on the telephone. Feedback cancellation should decrease or eliminate audible oscillation, thereby decreasing listener annoyance while at the same time allowing for additional gain, which could improve listener comfort and/or speech understanding. Automatic switches (available with some hearing aids) can detect the presence of a telephone that is held next to the hearing aid and switch the hearing aid automatically into the phone program, thereby minimizing listener effort. Other algorithms, such as those that de­crease unwanted background noise, may im­prove individuals’ listening com­fort and/or decrease listening effort on the phone, although these have not been investigated systematically. Given these new advances, it is not surprising that the age of the device correlated significantly (although weakly) with both hearing aid use on the telephone and the problems that individuals experienced on the telephone.

Of the individuals wearing older digital hearing aids (>5 years old), only 55% reported wearing their hearing aid on the phone, compared to 85% of individuals with new hearing aids (<1 year old). Additionally, 24% to 32% of individuals with older hearing aids reported regularly experiencing feedback, distortion, or buzzing compared to 4% to 7% of those with new hearing aids. Problems of insufficient volume also decreased, from roughly 60% to 32%, and difficulty understanding speech in noise dropped from 80% to 50% when comparing older to newer devices. There were no significant correlations between the ages of the hearing aids and participants’ ages or puretone averages (PTAs).

FIGURE 5. Percentage of calls made in different environments, as a function of phone type.

Hearing aid style. Those wearing custom devices, especially ITEs and ITCs, reported significantly more feedback on the phone than wearers of BTEs (Figure 4). This is likely due to the proximity of the hearing aid microphone to the hearing aid receiver, as well as proximity to the telephone receiver; as these distances de­crease, the potential for feedback increases. Hearing aid use on the phone reflected these results, with the device styles having the most feedback getting the least use (53% for ITEs, 63% for ITCs, 70% for CICs, and 73% for BTEs).

Phone programs. A total of 49% of individuals reported having a telephone program in their hearing aids—either a telecoil or an acoustic telephone program. (Note: Participants were not specifically asked whether their hearing aids had a telecoil or an acoustic phone program, as it was thought that most participants would not be able to answer this question.) While the larger device styles were more likely to have a phone program, use of this feature was similar across device style—an average of 43% of individuals who had a phone program used it. Those who did not use their phone program reported that it did not help (48%) or it was too much of a hassle (33%). Only one individual reported not knowing how to use the phone program. There were not any significant differences between users and nonusers of phone programs in the problems that they experienced using their phones.

Phone type. Users of cell phones made fewer calls in quiet, and more calls in challenging listening environments—in the car and outside—than users of home phones (Figure 5, page 20). Despite this difference, the percentage of people who used their hearing aids while on the phone was similar for both groups—64% for cell phone users and 68% for home phone users. Additionally, the type and degree of problems reported were similar for both groups.

Degree of hearing loss. Individuals with greater hearing loss were more likely to report feedback, distortion, and difficulty understanding speech with telephone use (Figure 6). Correlations for each of these were weak, but significant.

These results are not surprising. People with more severe hearing losses need more gain. With greater gain comes an increased risk of feedback and distortion/artifacts, which may in turn limit audibility and speech understanding. Those with more severe hearing loss also tend to exhibit greater speech processing deficits, which will also adversely affect speech understanding.

FIGURE 6. Percentage of individuals who regularly experienced various problems with telephone use, as a function of puretone average (PTA). Significant correlations are denoted with asterisks (P < .05* and P < .01**, respectively).

Problems During Phone Use

Problems of feedback, distortion, difficulty coupling a phone to the hearing aid, and insufficient volume all significantly, and negatively, affected whether people used hearing aids while on the phone. Figure 7 shows the percentage of individuals who reported regularly (usually or always) wearing their hearing aids while on the phone based on whether they regularly experienced these problems. For example, of the 24 individuals who said they usually or always experienced feedback, only ~45% of them regularly wore their hearing aids while on the phone. Of the 72 individuals who occasionally or never experienced feedback, almost 80% of them regularly wore their hearing aids while on the phone. In all, 27 of the 139 digital hearing aid wearers reported that they never wore their hearing aids on the phone, although 23 of these individuals still completed the questionnaire. Of these, 22 reported that they usually or always experienced one or more of the problems displayed in Figure 7. Therefore, one might infer that, if the problems of feedback, distortion, difficulty understanding, insufficient volume, and difficulty coupling were solved, hearing aid use on the phone may increase from approximately 30%-50% to 70%-80%.

Conclusions

Communicating on a phone is an important aspect of most people’s lives, and ensuring that hearing aid wearers have access to this ability is an important goal. Hearing aid wearers have historically identified phone use as one of their top complaints.

The survey summarized here was conducted to investigate how recent technological advances have affected phone use by hearing aid wearers. By integrating information across a variety of questions, we were able to conclude:

• Individuals using digital devices had far fewer problems on the phone than those wearing analog devices, with those wearing newer digital devices having the fewest problems.
• Individuals wearing BTEs had fewer problems than those wearing custom devices.
• Problems were similar for individuals who used a phone program (acoustic or telecoil) and for those who did not use a phone program.
• Hearing aid use on the phone was as prevalent for users of cell phones as it was for users of home phones.
• Even though people tended to use cell phones in more difficult listening environments than home phones, both groups experienced similar types and degrees of difficulty using their hearing aids on the phone.
• Individuals with milder losses had fewer problems than those with more severe losses.
• Individuals were more likely to use their hearing aids while on the phone if they did not experience problems doing so.

Modern hearing aid technology has improved telephone use for wearers of hearing aids by significantly reducing the problems of feedback, distortion, buzzing, insufficient volume, and speech understanding in noise. If technological advances continue to target these last two areas, which remain a challenge for 30% to 50% of hearing aid wearers, then we can look forward to further improvements in the user experience. In the future, wireless technology will likely play an increasing role in the development of these solutions.

FIGURE 7. Percentage of individuals who regularly wore their hearing aids while on the phone, as a function of whether they regularly experienced a particular problem. Significant correlations are denoted with asterisks (P <.05* and P <.01**, respectively).

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