Bilateral hearing loss va disability 2014,ringing in left ear sinus tract,tinnitus handicap questionnaire kuk university,immediate hearing loss in one ear newborn - Step 2

25.11.2013
Key words: asymmetric hearing loss, bilateral amplification, binaural advantage, directional hearing, hearing aids, localization asymmetry, monaural amplification, sensorineural hearing loss, sound localization, speech intelligibility. Abbreviations: ASYM = asymmetric hearing loss, BIA = bilaterally aided, BMLD = binaural masking level difference, CI = confidence interval, CROS = contralateral routing of signals, HL = hearing level, IID = interaural intensity difference, ITD = interaural time difference, LAI = Localization Asymmetry Index, MOA = monaurally aided, NH = normal hearing, OME = otitis media with effusion, SE = standard error, SEM = standard error of the mean, SNHL = sensorineural hearing loss, SNR = signal-to-noise ratio, SPL = sound pressure level, WDRMCC = wide dynamic range multichannel compression.
This material was based on work supported by the National Institute on Disability and Rehabilitation Research (grant H133G970107 and H133E01007) and The Smith-Kettlewell Eye Research Institute. Initially, a great deal of excitement existed over the prospect of improvement in speech intelligibility and localization with the use of bilateral hearing aids [6]. Two key advantages of bilateral amplification are directional hearing and improved intelligibility of speech and noise from different directions. Hirsh noted that the first true stereophonic hearing aid system was developed and patented by Soret in 1915 [7]. The first verifiable positive evidence of the bilateral advantage was found by DiCarlo and Brown [12]. By the 1960s, wearable bilateral hearing aids were readily available and with the introduction of ear-level hearing aids, interest in bilateral hearing aids was renewed [21].
This ruling, as well as the difficulty in objective demonstration of the binaural advantage with bilateral hearing aids, resulted in a decrease in recommendations for bilateral hearing aids as compared with monaural hearing aids.
Thus, as late as 1980, the view was that solid evidence for bilateral fitting was minimal and justification for the practice rested mainly on favorable subjective reports [25]. Many advantages exist for binaural hearing, although the advantages of bilateral hearing aids have not always been easy to prove objectively. In the past two decades, two findings have altered some of the traditional views of amplification. Second, Gatehouse found an improvement in speech recognition performance after some period of hearing aid use that was not noticeable immediately following the hearing aid fitting [38-39]. However, controversy exists concerning the extent to which a first-time hearing aid user must acclimate to hearing aids. Most of the research to date on acclimatization and deprivation has focused on speech perception. Acclimatization to input asymmetries has not been studied in great depth, which is surprising considering the widespread use of monaural amplification and the large number of individuals with asymmetric hearing loss (ASYM). The question of how well someone with hearing loss can localize sound (with or without amplification) is still not fully resolved. Accurate sound localization is a complex perceptual process that requires the integration of multiple acoustic cues [63]. Vertical localization and front-back discrimination rely on high-frequency spectral cues (>5 kHz) that are created by reflection and diffraction of sound by the external ear and, in particular, the pinna [69-70]. Investigators also argue that based on monaural listeners' ability to localize sound in the horizontal plane, spectral cues contribute to horizontal localization [70,74-75]. Recent studies of localization (or lateralization) abilities in sensorineural hearing loss (SNHL) listeners have been designed to either describe binaural deficits [4,78-82] or evaluate the effects of hearing aids and various amplification strategies [3,83-85], ear-mold configurations [3,83-86], and ear protectors [87]. Byrne and colleagues [49,81] found a moderate correlation between the severity of the hearing loss and the localization difficulty, and they concluded that unaided localization by SNHL listeners is affected by degree and type of hearing loss [91]. Aided localization has been shown to be better with the listener's own hearing aid(s) [84], which may be due to acclimatization [39,45-46].
Two studies tested localization in both quiet and noisy settings in listeners with bilateral, symmetric, high-frequency hearing loss [87,94]. Some caution is in order because, until recently, a multichannel expansion hearing loss simulation has not been used for evaluating the effects of the audibility of all frequency components of the localization stimuli [96]. Even with the benefit of WDRMCC, high-frequency hearing loss would limit access to higher frequency IID and spectral cues and force listeners to rely mostly on low-frequency ITD cues, which are more salient than IID cues [98]. Recent studies have raised the awareness of the importance of acclimatization in acoustic amplification. Investigators used the continuous-pointer method of measurement, which in experiments with NH listeners has been found to be superior in overall accuracy, response time, and error to other methods [101-102]. Simon et al.2 used the continuous-pointer method to study the localization of broadband and narrowband stimuli in the horizontal plane. Figure 1 shows perceived angle as a function of target angle for a broadband speech signal (multitalker babble, 250-4,000 Hz) for one NH and one BIA listener. The Localization Asymmetry Index (LAI) for a given set of data is defined as the average localization asymmetry over all the target angles in the study. This very small SE indicates the high sensitivity of the LAI in detecting asymmetries in localization errors. Determination of localization ability, in the unaided condition, of listeners with symmetric, bilateral hearing loss and long-term monaural amplification was of interest. Deprivation can be viewed as either a detrimental or a compensatory manifestation of auditory plasticity [104].
Another important consideration is the effect of monaural amplification on measures of binaural hearing. Eight SNHL listeners were tested: four monaurally aided (MOA) listeners with bilateral, symmetric hearing loss who wore a monaural hearing aid for more than a year and four with ASYM who wore bilateral hearing aids. Figure 3 shows the difference in hearing thresholds between the right and left ears for the BIA, MOA, and ASYM groups. The BIA listeners' right and left ear thresholds were also well matched, except at 4 kHz.
Figure 4 shows the perceived angle for a broadband speech signal (multitalker babble) as a function of the target angle for MOA listeners. The results for two of the MOA listeners were very poor, while data for one listener lies just outside the 95 percent CI for the BIA listeners. Generally, long-term use of a monaural hearing aid, even with a symmetrical hearing loss, can cause localization confusion when a listener is unaided. Figure 5 shows the perceived angle as a function of the target angle for the ASYM listeners. Figure 6 shows the LAI for four groups of listeners (seven NH and five BIA listeners from a previous study in addition to the four MOA and four ASYM listeners of this investigation). The work that has been discussed in this and previous articles [104] shows that BIA and NH listeners manifest very high degrees of symmetry (and negligibly small LAI values) in their judgments of perceived angle while the MOA listeners had relatively large LAI values. This article has shown that in the tide of the evolution of bilateral hearing aids we are now experiencing a flow of research, technology, and clinical application for this fitting option. Special thanks to Ervin Hafter, PhD, for generously allowing us access to the anechoic chamber at the University of California at Berkeley and Al Lotze for his help in data collection and analysis. I get 88 rounded up to 90.Separate line items are the only clue I can find to rate as bi-lat. I was just reviewing the explanations on my awards letter and it looks like the 10% scars rating is for 2 painful scars (3 or more would bump it up to 20%); and the 0% separate scars rating is specifically for linear scars that are not considered disabling.
Please forgive the interjection into the thread on behalf of myself but I've run into a brick wall as regards the computation of so-called 'bi-lateral' ratings.
Determining whether a bilateral hearing aid fitting is superior to that of a monaural hearing aid is a long-standing question; for this reason, the trend toward bilateral amplification has been slow.
This has important implications for those patients who receive monaural amplification during the ebb phase.
The importance of true binaural and the insufficiency of simple bilateral hearing aids have been emphasized.
This excitement was fueled by the studies of Hirsh [7-8] and Licklider [9] and the theoretical and clinical arguments of Bergman [10], Carhart [11], and DiCarlo and Brown [12]. Directional microphone hearing aids can also improve speech intelligibility under these conditions, and enthusiasm is growing for this form of amplification as discussed in the article by Todd Ricketts [14]. Almost since the development of the wearable electronic hearing aid (one that encompassed high gain, good reliability, and design flexibility), the issue of monaural versus bilateral fittings has been debated. The seminal work of Hirsh [19] and Licklider [9] precipitated the initial interest in bilateral amplification by specifying the gains in signal detectability and speech intelligibility that are produced by an interaural difference between the signal and the noise. They found that localization of a noise burst improved with bilateral amplification, although correlation of localization ability and speech intelligibility had not been demonstrated [20].
However, no consensus existed regarding the additional benefits of bilateral amplification. However, few people were willing to wear two bulky hearing aids and very few professionals were recommending them.
A fundamental weakness of early attempts to solve the monaural-bilateral controversy was that no well-established methodology existed to demonstrate the binaural advantage with bilateral hearing aids, especially with regard to speech intelligibility. The limited conclusive or compelling scientific evidence in support of bilateral hearing aids [32] has caused them to be used infrequently around the world [28,33]. However, a very important additional cost that is often overlooked is the deleterious effects of long-term monaural amplification.
First, Silman and colleagues, in a series of studies, reported significant changes in auditory function, specifically speech recognition ability, as a result of long-term monaural amplification or lack of bilateral amplification in people with symmetrical hearing loss [36-37].
This effect was attributed to acclimatization of the aided ear to the speech cues made available by the hearing aid. Some studies suggest that acclimatization occurs very rapidly or not at all since performance soon after the receipt of a new hearing aid is equivalent to that measured after months of experience [41-44]. It had been previously suggested that longer periods of acclimatization might be required for hearing aids with more complex signal processing [47-48]. Gatehouse and colleagues showed that the unaided ear of a hearing aid wearer tends to process low-intensity stimuli better than the aided ear [39-40,46].
The possibility that long-term input asymmetries may affect binaural processing was suggested by Moore [58] based on the following evidence: human adults can adapt to altered binaural cues that are produced by real or artificial asymmetries [4,59], the physiological responses of neurons in the higher levels of the central auditory system of animals remain plastic into adulthood and can be altered by lesions in the peripheral auditory system, and the bilateral balance of anatomic connections between auditory and brain stem nuclei continues to change in animals after unilateral peripheral lesions, at least into adolescence.


It is well known that normal-hearing (NH) listeners can localize well in both the horizontal and vertical planes. Localization on the horizontal or azimuthal plane depends primarily on binaural difference cues, interaural intensity differences (IIDs), and interaural time differences (ITDs) [64]. Source or head movement cues, cognitive cues [76], and visual cues [77] are also relevant in sound localization. They further found an interaction between degree of hearing loss and localization advantage with bilateral hearing aids [83].
As previously mentioned, numerous studies have compared aided localization among various hearing aid fittings and types of hearing aids.
Preliminary data suggest that the use of bilateral WDRMCC hearing aids does not interfere with localization in new hearing aid users; results for listeners tested with WDRMCC showed no significant difference in localization abilities from those of a group tested with bilateral linear hearing aids [97]. If the population is an older one, it is noted that the ITD cues are less salient [59,99-100]. As noted earlier, relatively little is known regarding acclimatization to asymmetric inputs such as from ASYM or long-term monaural amplification. Previous studies of localization accuracy with SNHL listeners used experimental paradigms in which the listener identified the sound source from a finite set of possible locations that were usually visible to the listeners. We assessed the frequency-dependence of localization ability with five NH and five bilaterally aided (BIA) SNHL listeners with symmetric, bilateral hearing loss. Note that bias to the left of the midline needs to be reversed in sign in order to maintain symmetry.
An LAI as small as 0.8° indicates statistically significant asymmetry in perceived angles for this particular listener.
We hypothesized that these listeners will have poorer localization ability than the NH and BIA listeners and will demonstrate significant asymmetries in their localization judgments as a result of acclimatization to long-term asymmetric (monaural) amplification. Recent work at The Smith-Kettlewell Institute has investigated input differences with the use of a number of different paradigms in asymmetric and symmetric SNHL and NH listeners.
While it might be expected that people with ASYM have adapted to their asymmetries for localization and lateralization [4,88], what happens to localization abilities for a  person with symmetric hearing loss after long-term monaural amplification as compared with long-term bilateral amplification? The right and left ear thresholds for the MOA listeners were symmetric with very small HL differences between ears.
The thick gray lines represent the 95 percent confidence interval (CI) for the BIA listeners and the bold dashed line represents the performance of an ideal observer. Only one MOA listener perceived angles within the BIA range, and even this listener showed some asymmetry in localization judgments on either side of the midline. This may be due to partial adaptation to the MOA condition and the combination of aided and unaided listening.
The perceived angles for three of the four listeners were well outside the 95 percent CI for BIA listeners. Whereas plots of perceived angle showed that only two of the MOA listeners fell well outside the range for BIA listeners, LAI values were consistently higher for the MOA listeners. Simon and Aleksandrovsky [4] and others [1-3] argued that the common assumption that two optimally fit monaural hearing aids constitute an optimum binaural fit is not necessarily true.
As recently as 1988, monaural hearing aid use for a few months, until the patient had become accustomed to wearing the aid, followed by a second hearing aid that is fit at a later date was still considered a viable option, although not necessarily the first choice [108]. Below is an image from my most recent rating wherein I received an increase for hearing loss right ear from 10% to 50% while simultaneously having made it a bi-lateral SC rating as well. However, it is now assumed that bilateral amplification has significant advantages over monaural amplification in most cases, a view that is supported by our localization results. The common assumption that two optimally fit monaural hearing aids constitute an optimum binaural fit is not necessarily true [1-5]. Since a true binaural hearing aid is not yet available, we will refer to all hearing aids fit for two ears as bilateral [4-5]. Following the initial enthusiasm, a down period occurred in the 1960s because of the lack of objective studies on improvements in speech intelligibility with bilateral hearing aids and the reluctance of consumers to wear two of the bulky instruments. This article is concerned with localization ability and the pros and cons of bilateral amplification. Knudsen [6] wrote positively about the potential value of bilateral amplification and created innovative variations of bilateral hearing aids such as the contralateral routing of signals (CROS) and split-band systems [15]. A hearing aid that would permit the listener to separately localize the speech and the noise and to attend separately to the desired signals was recommended; this would be possible if microphones were mounted on both ears. Theoretical arguments such as those by Hirsh [7] and clinical observations by others [10,22] supported the benefit of bilateral amplification; however, after six years of experimentation, no objective demonstration existed of the advantage of bilateral amplification for speech intelligibility in quiet and noisy situations [19,23].
One reason for this may have been a 1975 hearing aid industry ruling by the Federal Trade Commission [26]. For example, one of the first studies with positive results from bilateral amplification compared two ear-level hearing aids with a body-worn instrument [27], which was an inadequate control. Dillon states that this average fitting rate indicates what is being done, not what should be done [34], although the number of bilateral hearing aid fittings has risen. Markides, in an early classic hearing aid study, found that listeners with two ear-level aids had superior performance in speech discrimination, the squelch effect (3.39 dB), head shadow effects, and localization compared with listeners with one hearing aid [21]. Studies that do show an acclimatization effect indicate that it is incomplete even 10 to 18 weeks postfitting [39,45-46]. For example, deprivation has been demonstrated in studies of both children and adults; results from these studies show that long-term reduction in auditory stimulation can affect the BMLD. The smallest error for broadband sounds in a study by Makous and Middlebrooks [60] was 2° in the front and 9° at 60° azimuth in a two-dimensional head pointing task.
Directional shaping of the spectrum at low frequencies is also salient because of the effects of the torso [72].
This finding was attributed to inconsistent methodology between studies (presentation levels, stimuli, paradigms, listener practice levels) [89] and an inadequate separation of age, degree, type, and etiology of the hearing loss. Earlier studies showed that when sounds are presented at clearly audible levels, aided localization was worse than unaided localization [21,83]. Noise decreased performance in both listener groups but only with low-frequency narrowband signals, which suggests that audibility ensures the availability of high-frequency IID but not ITD cues.
Localization performance was only slightly poorer for SNHL listeners than for NH listeners with noise at 0° azimuth.
If wideband stimuli are produced with conflicting IID and ITD cues, listeners follow the direction of the ITD cue as long as the stimuli include low frequencies. A series of investigations has been undertaken at The Smith-Kettlewell Eye Research Institute for determining the effects of long-term asymmetric inputs on sound localization [4,59]. Imposition of a finite response set introduces quantization error that can reduce accuracy. Stimuli were presented at a sound pressure level (SPL) of 80 dB, which was audible to all the SNHL listeners. The listeners are typical in that their localization errors fell in the middle of the range for each group. In an acoustic pointing task, when slight asymmetries at the two ears produced signals of equal sensation level but unequal SPL, lateralization was towards the ear with the greater SPL signal regardless of the ear to which the signal was delayed by an ITD [59]. The use of monaural amplification, therefore, has ramifications for unaided as well as aided localization the degree that might be dependent on the duration and consistency of the use of monaural amplification.
These data show that asymmetry in localization judgments is a much more sensitive indicator of abnormal localization ability than the magnitude of localization errors. The importance of true binaural and the insufficiency of simple bilateral hearing aid fitting have recently been emphasized [4-5]. In contrast, this article has shown, on the basis of recent research and clinical and theoretical arguments, that bilateral hearing aids should be the first choice for maximization of localization ability [34]. Hearing aids-A review of past research on linear amplification, amplitude compression and frequency lowering [ASHA Monograph].
Perceived lateral position of narrow-band noise in hearing-impaired and normal-hearing listeners under conditions of equal sensation level and sound pressure level. The effect of combining low- and high-frequency passbands on consonant recognition in the hearing impaired. A comparison of the effect on consonant discrimination of combining low- and high-frequency passbands in normal, congenital, and adventitious hearing-impaired subjects.
Long-term effects of monaural, binaural and no amplification in subjects with bilateral hearing loss.
The time course and magnitude of perceptual acclimatization to frequency responses: evidence from monaural fitting of hearing aids. Outcome measures for hearing aid evaluation-properties and requirements in acclimatization research. Role of perceptual acclimatization in the selection of frequency responses for hearing aids.
Spectral changes produced by earphone-cushion reproduction of hearing aid-processed signals.
The time course of effects on intensity discrimination following monaural fitting of hearing aids.
Short-term and long-term effects on the masking level difference following middle ear surgery. Plasticity of binaural hearing and some possible mechanisms following late-onset deprivation. Perceptual consequences of engineering compromises in synthesis of virtual auditory objects [abstract]. Speech recognition in listeners with impaired hearing: effects of listening paradigm [abstract].


Effects of reference interaural time and intensity differences on binaural performance in listeners with normal and impaired hearing. Discrimination of interaural temporal disparities by normal-hearing listeners and listeners with high-frequency sensorineural hearing loss. Effects of long-term bilateral and unilateral fitting of different hearing aid types on the ability to locate sounds. A comparison of different binaural hearing aid systems for sound localization in the horizontal and vertical planes. Improvement in aided sound localization with open earmolds: observations in people with high-frequency hearing loss. Effects of sensorineural hearing loss on interaural discrimination and virtual localization. In this article, we will address the advantages of bilateral hearing aids and reveal some new localization data that show that most listeners with bilateral amplification, when tested unaided, as well as normal-hearing listeners manifested very high degrees of symmetry in their judgments of perceived angle while listeners who routinely use monaural amplification and those with asymmetric hearing loss had relatively large asymmetries.
With time, enthusiasm wanes as expectations are not met and new studies illuminate newer insights and more realistic outcomes. However, the enthusiasm for bilateral amplification has resurfaced and in the past decade more bilateral than monaural hearing aids have been dispensed [13]. Otherwise, hearing-impaired listeners would continue to find their hearing aids useless in noisy situations [8]. An exception to the fitting of bilateral hearing aids was made with children who, in the late l960s, were routinely fit with two body-worn hearing aids or, at worst, a Y-cord arrangement. Levitt suggested that contrasting the subject's performance with optimally prescribed ear-level monaural versus optimally prescribed bilateral hearing aids would be a reasonable comparison [28].
He cautions that for various reasons not everyone who receives two hearing aids wears them.
The summation of the two signals also permits reduced amplifier gain, which results in fewer potential feedback problems. It is likely that other stimulus or input deprivation effects are subtler, yet at least as significant, and they may be manifested by changes in binaural as well as monaural processing, such as localization.
All of these acclimatization studies, however, were performed with conventional linear hearing aids. Reduced BMLDs have been observed in children who had normal hearing when they were tested but who had a history of hearing loss associated with otitis media with effusion (OME) [53]. Thus, a lateral shift of the auditory image is produced by ITDs in low but not high frequencies. Listeners with high-frequency hearing loss have more difficulty than NH listeners when tested in the sagittal plane and with elevation [73].
Aside from these methodological issues, general localization and lateralization performance was not easily predicted on the basis of the audiogram, although it was degraded in listeners with SNHL and, in particular, those with presbycusis, unilateral hearing loss, and bilateral asymmetry [88]. Studies by Koehnke and colleagues advocate that the audiogram of the SNHL listener is neither a good predictor of binaural abilities (not localization per se) nor is performance predictable from one binaural test to another [3,79,90].
At ±90° azimuth, localization performance of the SNHL listeners decreased at a higher SNR than for NH listeners and was less consistent at ±90° than at 0° azimuth.
Localization in the horizontal plane is of particular interest because of the remarkable sensitivity of the auditory system to small differences in angle of azimuth. The visual cues provided by readily visible reference points (especially a set of speakers that correspond to the sound sources) can powerfully influence apparent sound position [103]. We were also interested in investigating asymmetries in localization of listeners with ASYM with the techniques just described. In a second paradigm, a graphic pointing task, the perceived lateral position was found to linearly depend on the degree and direction of the threshold asymmetry when the listener was equalizing by sensation level [4]. Even the subject whose perceived angles were fairly close to those of the BIA listeners had significantly asymmetrical localization judgments. All statistical tests that evaluated the significance of the LAI values were conducted with the use of the Bonferroni adjustment to account for multiple comparisons. The bilateral factor will be applied to such bilateral disabilities before other combinations are carried out and the rating for such disabilities including the bilateral factor in this section will be treated as 1 disability for the purpose of arranging in order of severity and for all further combinations.
Can someone here please tell me if, when and how I should consider entertaining the notion of the inclusion a bi-lateral computation for the purposes of 'increasing' my numbers. A gradual settling down follows in which both the potential and limitations of these developments are recognized; this results in a new generation of sensory aids that embody significant, albeit undramatic, improvements.
Other methodological issues that contributed to the long-standing controversy about the benefits of bilateral amplification (see Byrne [25] for an excellent review of the controversy) included lack of research on acclimatization [29-30], selection of appropriate tests sensitive to differences in hearing aid conditions, selection of methodologies that demonstrate binaural advantages [27], and choice of presentation level [31]. In a 1999 National Acoustic Laboratories of Australia study of 4,000 patients, only 48 percent had been fitted with bilateral hearing aids [35].
People with severe hearing loss may have difficulty achieving appropriate loudness for speech with the lack of summation inherent to a monaural fitting. Although the BMLDs of these children returned to expected levels, which presumably demonstrates their incorporation of normal binaural auditory cues with experience [54], this finding suggests a slow recovery of binaural function after deprivation. However, controversy exists regarding how well hearing-impaired listeners can localize sound.
However, ITDs can still be used in the high frequencies when there are discernible features in the signal envelope. Middlebrooks suggested that accurate horizontal localization was basically unaffected by the imposition of the narrowband spectral peak and that horizontal judgment depended almost entirely upon IID cues because of the high center frequencies of the stimuli [71]. In the continuous-pointer method, the number and location of loudspeakers are unknown to the subject who manually moves a visual pointer with a slider potentiometer to the perceived location of the auditory signal. These listeners were consistent in their judgments as shown by the relatively small test-retest SEs. In light of this result, we were very interested in examining the effects of asymmetric inputs on the accuracy of localization ability and localization asymmetries, in particular. Equalization by SPL showed no such dependency but produced images that were lateralized close to the midline.
The results for the MOA and ASYM listeners show large individual differences that were not previously seen with either the BIA or NH listeners.
Since the errors were highly asymmetric, the LAI indices for this group were large, much larger than the average error (bias) in localization judgments.
For example, with disabilities evaluated at 60 percent, 20 percent, 10 percent and 10 percent (the two 10's representing bilateral disabilities), the order of severity would be 60, 21 and 20. Three months after fitting, 20 percent of the patients that were fit bilaterally reported wearing only one hearing aid. Reduced BMLDs have also been observed in children and adults years after corrective surgery for both OME and otosclerosis has equalized the hearing levels (HLs) in the two ears [55-57].
The fact that localization on the basis of interaural timing information is possible for complex, high-frequency stimuli, such as transients, noise, and amplitude-modulated signals, has challenged the duplex theory [66-68]. However, in the Byrne study, no correlation existed between aided and unaided localization score and frequency pure-tone average, although it should be noted that half of the fittings in the study were monaural [91]. This is a more natural response since no mental transformation of the target is required and listeners can use their own anatomical reference points [101]. The results of these two studies suggest that people with asymmetric hearing, normal or otherwise, have adapted to their asymmetry for IID in lateralization tasks.
123) is that, although most listeners with moderate hearing loss have good to excellent accuracy of localization, some will always have difficulty localizing sound, possibly as a result of monaural amplification or poorly fit bilateral hearing aids. The 60 and 21 combine to 68 percent and the 68 and 20 to 74 percent, converted to 70 percent as the final degree of disability.(a) The use of the terms “arms” and “legs” is not intended to distinguish between the arm, forearm and hand, or the thigh, leg, and foot, but relates to the upper extremities and lower extremities as a whole. In some cases, evolution can be very rapid, as in the case of the cochlear implant; in other cases, the evolutionary development is slow and spans many decades. Still, Dillon states there is now overwhelming evidence that two hearing aids provide better performance than one in most situations [34].
Also, when wideband stimuli are produced with conflicting IID and ITD cues, listeners follow the direction of the ITD cue as long as the stimuli include low frequencies [63].
The continuous range of possible responses eliminates the context effects of identification paradigms.
In addition, the decreased localization ability may be seen in the unaided situation, especially with monaurally fit individuals. These significant advantages make this paradigm an important contribution to the accurate measurement of the localization percept.
Typical for localization errors, these errors increased with increased target angle for both listeners; the magnitude of the error was greater for the BIA listener. Although there were significant individual differences in the magnitude of the localization biases, the majority of listeners in each group showed biases in the same direction, away from the midline for the NH group and closer to the midline for the BIA group. We are hopeful that basic and clinical research regarding these issues of binaural and bilateral advantages will continue on the present scale.
Thus, some relationship between the two hearing aids in either time or intensity is being advocated.
Digital binaural hearing aids with considerable flexibility in controlling the signals that reach each ear have recently been introduced. The LAI, because of its simplicity and great sensitivity, should prove to be a useful tool in establishing how well a person fitted with a true binaural hearing aid is able to localize sound and in establishing fitting procedures for true binaural amplification.




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