A closer look at the sounds deemed “uncomfortably loud.”
|Gitte Keidser, PhD, is a senior research scientist and Elizabeth Convery, MS, is a senior research audiologist at the National Acoustic Laboratories (NAL) in Sydney, Australia; Jürgen Kiessling, PhD, is a professor and director of the Department of Audiology, Justus-Liebig University, Giessen, Germany; and Ruth Bentler, PhD, is a professor in the Department of Communication Sciences and Disorders at the University of Iowa.|
Among irregular hearing aid users, or non-users who have tried but rejected a hearing aid, at least 50% are dissatisfied with the instrument in noisy disturbing situations.1-4 Even among generally satisfied hearing aid users, 26% were dissatisfied with the comfort of loudness.5 This is despite the fact that most modern hearing instruments feature multichannel wide dynamic range compression (WDRC) and output limiting, and that noise management features designed to improve the signal-to-noise ratio (SNR) or to target transient noises, are widely available.
In a recent collaborative study between the University of Giessen (UG), the University of Iowa (UI), and the National Acoustic Laboratories (NAL), it was found that, when prompted, many current hearing aid users reported experiencing loudness discomfort in real life. The finding was surprising because the measured gain for average input levels and the output levels of the study participants’ instruments were, on average, below the NAL prescriptions for gain6 and output7 by 4.9 and 10.7 dB, respectively. This paper takes a closer look at the sounds deemed uncomfortably loud and questions whether the hearing instrument is always to blame.
Sounds Reported To Be Uncomfortably Loud
A total of 56 participants were recruited across three continents to evaluate a hearing instrument output verification (OVer) test.8 Participants were experienced, bilaterally fitted hearing instrument users. The group consisted of 25 females and 31 males ranging in age from 39 to 86 years, with a mean age of 69 years.
Before completing the OVer test, the participants were asked if they had experienced loudness discomfort in real life while wearing their current hearing instruments. If the reply was affirmative, they were asked to provide examples of sounds that caused loudness discomfort and to indicate how frequently they were exposed to such sounds (“rarely,” “occasionally,” or “frequently”). A total of 82% of participants indicated that they had experienced some loudness discomfort while aided. Sounds that were reported to cause loudness discomfort were many and varied, and without knowing what sounds are considered uncomfortably loud by the general population, it was difficult to draw a valid conclusion from the list of sounds.
Consequently, a follow-up investigation was carried out at NAL to determine whether the sounds reported by hearing aid users to be uncomfortably loud were specific to aided listeners, or whether a group of mature adults with normal hearing also considered such sounds to be uncomfortably loud. Twenty adults with normal hearing from families of employees at NAL were recruited, and they were asked whether they had experienced loudness discomfort in real life. The normal-hearing group consisted of 11 females and nine males ranging in age from 50 to 67 years, with a mean age of 60 years. Interestingly, a similar percentage (85%) of these mature adults with normal hearing reported experiencing loudness discomfort in real life. The reported frequency with which loudness discomfort was experienced in real life was also well matched across the two populations (Figure 1).
|FIGURE 1. The distribution by percentage of hearing aid users and normal-hearing participants experiencing loudness discomfort, and the frequency in which they experience loudness discomfort.|
|TABLE 1. The percentage of hearing-impaired (HI) and normal-hearing (NH) participants who reported a specific situation within each sound category to be uncomfortably loud in real life.|
The sounds perceived as uncomfortably loud were divided into seven broad categories:
- Transportation vehicles;
- Wind noise;
- Aircraft; and
- High-frequency (HF) and/or sudden sounds.
Table 1 shows the percentage of aided hearing-impaired and normal-hearing listeners who reported real-life loudness discomfort in response to at least one sound within each category. Half of the hearing aid users found sounds in the people/groups category uncomfortably loud, and more than 40% of both aided hearing-impaired and normal-hearing mature listeners reported experiencing uncomfortable loudness in response to situations in the entertainment category.
Table 2 lists the specific situations we classified as people/groups, transportation vehicles, entertainment, tools/machines, and HF and/or sudden sounds. Looking across the columns of specific situations, it appears that it is very much the same types of sound sources and environments that cause mature adults to experience loudness discomfort, irrespective of whether they are aided or have normal hearing. The main exceptions include discussions with several people (people/groups category), some electrical household appliances (tools/machines category), and a range of sudden transient sounds (HF and/or sudden sounds), which were mentioned only by hearing aid users.
|TABLE 2. The specific situations within each sound category reported to cause loudness discomfort in real life by hearing aid users and normal-hearing adults. Numbers in brackets indicate the number of participants using the particular phrase to describe an uncomfortably loud situation.|
Sound Levels Recorded in Real Life
The big unknown factor in the above data is the sound pressure level (SPL) of the uncomfortably loud sounds at the time they were experienced. Figure 2 shows the range of input levels recorded for sound sources representative of six of seven sound categories in Table 1, with some specific examples marked along the ranges. The levels refer to the long-term equivalent root-mean-square (Leq) levels reported in a handful of papers, each of which reported the overall sound levels measured for a variety of environments and sound sources.9-13 The purpose of obtaining the recorded levels varied across publications, and therefore the range of targeted environments varied by study. In addition, unpublished sound levels for 78 different sound sources were obtained from NAL and the Technical University of Denmark.14 At both laboratories, the levels were obtained during on-location recordings from a listener’s natural position in relation to the sound source. It should be noted that the input levels in Figure 2 are only a guide, as many of the specified sources could produce higher or lower levels depending on the proximity of the listener to the sound source and the duration of exposure.
|FIGURE 2. An indication of the range of input levels produced by sound sources falling within six sound categories in which adults report sounds to be uncomfortably loud. Specific sources are noted along the input level ranges.|
Generally, the data in Figure 2 suggest that sounds and situations perceived as uncomfortably loud can produce levels above 80 dB SPL. Apart from levels recorded at some live music performances (105-110 dB SPL), the three highest recorded input levels among the representative sound sources were obtained for a bumpy train ride (97.0 dB SPL), a bus ride (95.1 dB SPL), and a (fast) car ride (94.7 dB SPL).
In this context, it is also worth mentioning the work by Neitzel et al.15 Neitzel and colleagues obtained dosimetry measurements and simultaneous activity log data from 112 people during two different study phases. During phase one of the study, 40 consecutive hours of noise measurements were obtained during the workday from 81 workers in eight trades, while in phase two of the study, 96 consecutive hours of noise measurements, starting on a Thursday morning, were obtained from 31 workers in six trades. The mean age of the participants was 29.6 years. The noise measurements were analyzed in 1-minute samples, and a distinction was made between occupational and non-occupational activities. Non-occupational activities were further grouped into six activity categories for which the percentage of activities falling into each category across the two studies was provided: bar/restaurant/shopping/theater (2%), home (50%), listen to music/watch TV (23%), travel in a car/bus (14%), yard work (10%), and other (1%). There are no particular reasons to think that this distribution of activities would be much different for a more mature population like the one from whom the data in Table 2 was collected.
Figure 3 shows, for each of the activity categories, the percentage of recorded minutes that were below or equal to 70 dB(A), between 70 and 80 dB(A), between 80 and 90 dB(A), and above 90 dB(A). Overall, 79% of recorded minutes were below 70 dB(A), while only 1% exceeded 90 dB(A). Home activities were associated with the lowest levels, while travel in a car or bus was associated with the highest percentage (24%) of reported minutes above 80 dB(A). The latter activity also presented the highest percentage (4%) of reported minutes exceeding 90 dB(A).
|FIGURE 3. The percentage of recorded minutes identified to belong to each of six different sound categories falling into four ranges of input levels. The graph is reproduced from Table II in Neitzel et al.15|
Overall, data suggest that situations associated with socializing, entertainment, and transportation are among the most commonly reported situations causing loudness discomfort for the mature adult population. On average, such activities are likely to account for about 40% of their leisure time and, for about a quarter of mature adults, to cause loudness discomfort on a frequent basis.
While such activities certainly can produce input levels above 90 dB SPL, the average percentage of time people are exposed to such high levels appears to be small. In comparison, the average loudness discomfort level measured on younger listeners with normal hearing when listening to broadband stimuli, such as speech or random noise, has consistently been above 90 dB SPL when converting the reported coupler levels to levels in the free field.16-19
It seems that many of the sounds perceived as uncomfortably loud—such as motorized vehicles, live music performances, large gatherings, and power tools—are also sounds that are likely to exceed 80 dB SPL, and infrequently 90 dB SPL. It is interesting that many of the sounds reported to cause loudness discomfort by hearing aid users are also experienced as being uncomfortably loud, with similar frequency of occurrence, by normal-hearing adults of a similar age. This finding agrees with observations by Palmer et al20 that aided ratings of aversiveness by hearing aid users exceeded unaided ratings, but tended to be similar to normal-hearing listeners’ ratings.
While it is the job of the clinician to ensure that the hearing aid does not cause unnecessary loudness discomfort, the question remains: Can the occasional loudness discomfort experience be avoided without compromising the overall sound quality of other, perhaps more important, sounds? Data collected on the gain preferences of hearing aid users have suggested that they would prefer all sounds to be delivered within a narrow, comfortable listening range.21 But is aiming for a narrow range of output levels in hearing aid fitting a practical and sensible approach? Remember that an output level set too low can distort speech presented at 70 dBSPL.7 Rather than attempting to eliminate all loudness discomfort from the listening experiences of the aided person, a more sensible goal may be the evaluation of a loudness discomfort experience as simply less severe than for the average normal-hearing person.
Proportionally, there were more aided hearing-impaired than normal-hearing participants reporting loudness discomfort in the People/groups category. Some of the specific situations mentioned in this category by aided listeners, such as discussions with several people and specific voices, are somewhat curious. These situations are unlikely to present levels above 80 dB, and it is speculated that the listeners respond to negative aspects of the sound other than loudness discomfort. For example, when presenting the aided participants with cocktail party noise during the hearing aid OVer test,8 some commented on the inability to understand speech in such situations after they had pressed the “unacceptably loud” button, and mentioned nothing about the loudness.
That the aided participants may have had difficulty separating loudness discomfort from other attributes is further highlighted by such participant comments about the sound of vacuum cleaning as “my wife is constantly vacuuming at home” and finding vacuuming an “unpleasant task.” It could be argued that this confusion is more likely in the aided population, who presumably have a stronger subconscious awareness of having problems hearing.
When questioning the client about loudness discomfort, the clinician should bear in mind that the client’s definition of this term may be more holistic and encompass other aspects of discomfort besides loudness (eg, sounds being unexpected, unpleasant, associated with negative experiences or emotions, intrusive upon speech understanding, etc). Further, according to Berglund et al,22 the degree of annoyance or disturbance caused by some sound sources may depend on the activity at the time of exposure, attitude toward the noise source, noise sensitivity, and controllability of the stressor.
A relatively high proportion of both aided and normal-hearing mature adult listeners reported experiencing loudness discomfort from situations in the entertainment category. Given that such situations seem to make up a relatively small percentage of leisure activities, it would seem unjustifiable to allow the hearing aid output level to be adjusted to cope specifically with loud music/audio presentations. Further, many of these situations can potentially be controlled by aided persons by using a volume control or a tailored “entertainment” program, or by turning off the hearing instruments. Ear plugs would be a possible solution for both hearing-impaired and normal-hearing listeners when attending loud entertainment venues. A more desirable solution, of course, would be to convince organizers of such events to reduce the sound level to make the experience more pleasant and healthy for the ears.
The most frequently experienced sound source that exceeds 90 dBSPL appears to be traveling in transportation vehicles. Interestingly, none of the surveyed listeners mentioned riding in a transportation vehicle as a source for loudness discomfort. Maybe none of our recruits were regular public transport users (trains and buses), or the term “traffic noise” was used loosely to cover any situation dominated by transport machinery. It is also possible that because sounds produced by motor vehicles typically have a lot of energy at very low frequencies (<100 Hz), which is outside the frequency range efficiently amplified by hearing aids, the noise was not perceived as intrusive, at least by the hearing aid users.
Only aided listeners mentioned sudden, transient sounds as causing loudness discomfort. As many transient sounds are high-frequency weighted, the protection by the acoustic reflex in listeners with normal hearing cannot entirely explain this discrepancy, and it is possible that the transmission of such sounds through the hearing instrument is largely to blame. Consequently, the recent introduction of noise reduction algorithms that specifically target transient non-speech sounds23 may prove useful for a portion of the aided listeners.
More than 80% of both aided hearing-impaired and normal-hearing mature adults reportedly experience loudness discomfort in real life, despite the aided population being fitted with acceptable gain and output levels. With a few exceptions, the sound sources and environments reported to be uncomfortably loud were the same across the two populations. Sounds deemed uncomfortably loud included, in particular, sounds associated with entertainment, large gatherings, and machinery capable of producing input levels in excess of 90 dB if experienced at a close proximity.
While it is important to ensure that hearing instruments do not cause loudness discomfort to occur, it is questioned whether it is possible to completely avoid experiences of infrequent loudness discomfort without compromising the sound quality of such important sounds as speech. In addition, it is speculated that aided adults, perhaps due to their subconscious awareness of having problems hearing, have difficulty separating loudness discomfort from some other negative aspects of sounds, such as annoyance or disturbance.
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Correspondence can be addressed to HR or Gitte Keidser, PhD, National Acoustic Laboratories, 126 Greville St, Chatswood, NSW 2067, Australia; e-mail: .
Citation for this article:
Keidser G, Convery E, Kiessling J, Bentler R. Is the Hearing Instrument to Blame When Things Get Really Noisy? Hearing Review. 2009;16(8):12-19.