Binaural Aids Research Articles

Evaluation of a prototype beamforming binaural hearing aid

A computerized version of the California consonant test [Terry etal., Ear Hear. 13, 70–79 (1992)] was used to evaluate a wearable digital beam-forming binaural hearing aid. The binaural aid uses an analysis–synthesis method where phase and magnitude cues, derived from microphone placement at the ears, are used to attenuate sounds from locations other than the 0-deg azimuth position. Normal hearing subjects, with their left ear occluded to reduce binaural cues, were used together with hearing impaired subjects for evaluation. Speech at 0 azimuth was presented via loudspeaker at 50 dBA. In the noise condition four talker babble at 35-deg azimuth (54 dBA) was mixed with the target speech. The hearing aid was programmed to give a basic 6-dB/oct preemphasis. Overall gain for the hearing impaired subjects was initially adjusted to give approximately a 70% intelligibility score for the speech alone condition. Subjects were instructed to maintain body and head position while responding to word choices shown on a screen positioned above the target speaker. Both subject groups showed a relative improvement in intelligibility and response times for the beam processing mode in the speech in noise condition.

One aid or two?—more visits please!

A prospective trial of hearing aid provision was undertaken to define factors which might be used to allow hearing aids to be fitted optimally. Patients referred for the provision of a hearing aid were studied prospectively at each of five visits when they were questioned by means of a proforma. Fifty-six patients completed the trial and gave adequate responses for analysis. No audiometric or symptomatic criteria were found to be of use in predicting the final choice of hearing aid combination. It may be that initial sequential monaural aiding leads to a higher uptake of binaural aids in the long term. Patients valued multiple visits to the clinic and sequential trials of monaural aiding, the majority felt that binaural aids should be tried.

My love affair with Ruth Bender

In 1982, The American Auditory Society saluted J. Donald Harris as its Renaissance Man. His unique ability to combine science and the humanities is exemplified in his chapter, “My love affair with Ruth Bender: A history of binaural aids for babies” [Harris, in Binaural Hearing and Amplification, edited by Libby (Zenetron Inc., Chicago, 1980)]. Binaural hearing was a subject very dear to his heart and he praised the pioneering work of Ruth Bender and others in fitting infants and young children with two hearing aids. Dr. Harris served as mentor and major advisor to the writer during the time he was an adjunct professor at CUNY. He supervised her dissertation that compared discrimination scores when a low‐ and high‐pass band of speech was presented to the same ear or opposite ears of normal‐hearing subjects. This study was subsequently replicated by the writer with hearing‐impaired individuals, both congenital and adventitious. This paper will present an overview of this research and will conclude with a study that investigated the use of split‐band amplification—high frequencies in one ear and low frequencies in the other. The writer received ongoing advice, encouragement, and support from J. Donald Harris for her research. The passing of our Renaissance Man has left an unfillable void for many.

Binaural benefit--when and how much?

Subjective ratings of aided hearing ability on a five point scale in ten hypothetical listening situations were obtained from 150 binaural hearing aid users, and from 296 monaural hearing aid users. Ratings of unaided hearing ability in nine of the same situations were obtained from 125 persons with self-defined normal hearing. The results indicated that in situations where signal-to-noise ratio was low, hearing aid users rated their listening much below the performance of normal hearing persons, binaural users indicating no advantage over monaural users. In the other hypothetical situations the binaural users rated their ability higher than did the monaural aid users. In some situations, where the sound was presented from a single source, binaural aid users rated their ability on a par with the normal hearing individuals. Age and hearing loss had small effects on the ratings, but the magnitudes of these effects were considerably less than that attributable to the type of aid provision, that is, whether monaural or binaural. These findings lend support to the benefits of binaural amplification in many listening situations.

Survey of binaural hearing aid users.

Two hundred four subjects supplied with binaural hearing aids through the British National National Health Service were surveyed by means of a postal questionnaire regarding their use of, attitudes of, and satisfaction with the two aids. The majority were using both aids regularly and extensively, and with high levels of satisfaction. Background noise was identified as the acoustic environment creating the greatest difficulty. Wind noise especially was a problem, although a few subjects had devised ways of coping. Significantly better attitudes within the family were reported by the good users, but it was not possible to establish which was cause and which effect. Binaural aids were reported as being significantly better than monaural aids in reducing the problems associated with tinnitus, which was present in almost half the subjects surveyed. Undoubtedly the majority of the patients reviewed believed that their auditory performance, social competence, and personal enjoyment of life were enhanced since changing to binaural aids.

Evaluation of Binaural Hearing Aids in Children Using Localization and Speech Intelligibility Tasks

Because of an assumed relationship between localization and speech intelligibility in noise it has been suggested that a localization test provides a suitable measure for the evaluation of binaural aids in everyday situations. The present study shows a significant correlation (a) between binaural advantage in a localization task and the binaural advantage in speech intelligibility in noise task, and (b) between binaural advantage in judgement of separation of speech and noise and binaural advantage in a speech intelligibility in noise task. However, neither relationship was strong enough for accurate individual prediction of binaural advantages in speech intelligibility. Possible reasons for this are discussed, and the lines that further research might follow are suggested.

An Influence of Binaural Hearing Aids on Positioning of Sound Images

An influence of binaural hearing aids on positioning of sound images produced by signals from two loudspeakers was investigated with normally hearing and hearing-impaired subjects. The image can be positioned along a horizontal line connecting the centers of the sources by adjusting the relative sound pressure levels of signals. When the listener is a symmetrical receiver, the image appears on the midline (0 degrees azimuth) for equal levels or away from the midline for unequal levels. Any asymmetry of the receiver causes a shift of the image away from the midline. In the study, the level differences, delta Ls, necessary to position sound images at 0 and +/- 12 degrees azimuths were measured. The baseline data were collected for 10 normally hearing subjects in unaided and aided conditions. In the aided conditions binaural aids were balanced (equal gains) or unbalanced (10 dB disparity in gains). The normally hearing subjects positioned the image on the midline with a group mean delta L of 0 dB in both unaided and balanced aided conditions. To position the image at +12 or -12 degrees azimuth they needed mean delta Ls that could be predicted from a theoretical equation. With unbalanced aids, a group mean delta L of +3 or -3 dB was needed for the midline image. The delta Ls for the side images also were shifted. For 12 hearing-impaired subjects with bilateral lossses, the midline delta Ls in unaided condition were within the normal range (+/- 2 dB). For two monaural hearing aid users with long experience, the midline delta Ls were greater than normal. The delta Ls for the side images were equal to or greatr than delta Ls for normally hearing subjects. In aided balanced and/or unbalanced conditions, some hearing-impaired subjects needed delta Ls for the midline image outside the normal range, and some could not position the image at the side azimuths. It was concluded that the binaural hearing aids can be a source of receiver asymmetry.

Psychological aspects of patients with binaural hearing aids.

9 of 10 persons with hearing defects can only overcome this handicap through the use of hearing aids. Only a small group needs body aids, binaural ear-level aids should be the routine for all the rest. In order to prevent deprivation of the acoustic sense, the whole hearing organ should be stimulated from the very beginning of the treatment with an aid in the right and in the left ear. Through routine prescription of binaural aids from the start, the psychological problem based on hearing aid use would be overcome.

Directional Hearing with Hearing Aids

The ability to locate broad band noise in the horizontal plane was measured in an anechoic room with monaural and binaural hearing aids in 13 children 8 to 16 years of age.Children with a single aid showed very poor results, and it was not possible to demonstrate any convincing improvement in directional hearing by the use of binaural aids.In experiments with 3 adults with normal hearing, some advantages in angular localization with binaural aids over monaural aid were observed. There was no significant difference between the results with binaural bodyworn aids and behind-the-ear aids and results with directional and conventional microphones.

The effects of microphone spacing on auditory localization.

The localization ability of 10 normally hearing adults was determined under varying microphone separations and varying sound source azimuths. The stimuli (white noise busts) were prerecorded, after being transduced through 'body' hearing aids and then played to the subjects over headphones. Results indicated that there was an improvement in localization ability for all azimuth conditions when the microphones were spaced wider than 12.7 cm apart (15.2-30.5 cm). The smaller the separations (5.5-12.7 cm), the poorer the localization. Localization was always poorer at 30 degrees azimuth (the smallest used) than at any of the other azimuths (0 degree, 30 degrees, 60 degrees, 90 degrees right and left), regardless of microphone spacing. Implications are made about the relation of these findings to the use of binaural body aids on infants and young children.

Presbyacusis, Hearing Aids and Aging

This paper considers the factors of presbyacusis and age-related psychological changes in older adults in terms of their effects on the use or potential use of hearing aids as a means of improving aural communication. Data are presented on the prevalence of hearing impairment and the extent of hearing aid use in aging listeners. Four major classes of presbyacusis are described (sensory, neural, metabolic, and cochlear conductive) and a hearing aid prognosis is made for each type of disorder. It is shown that aging produces deficits in pure-tone thresholds, the speech reception threshold, and speech discrimination, but not all losses can be 'corrected' with a hearing aid. Binaural (stereophonic) devices are psychoacoustically superior to monaural devices; however, behavioral and personality changes in older patients often create problems of adaptation to the binaural aid. These changes may also affect the fitting of an aid and the patient's ability to learn to use it. Some practical suggestions are offered on the evaluation of hearing aids and it is emphasized that adequate orientation and counseling are typically required if hearing aid treatment is to be successful in presbyacusis.

Presbyacusis, Hearing Aids and Aging

This paper considers the factors of presbyacusis and age-related psychological changes in older adults in terms of their effects on the use or potential use of hearing aids as a means of improving aural communication. Data are presented on the prevalence of hearing impairment and the extent of hearing aid use in aging listeners. Four major classes of presbyacusis are described (sensory, neural, metabolic, and cochlear conduvtive) and a hearing aid prognosis is made for each type of disorder. It is shown that aging produces deficits in pure-tone thresholds, the speech reception threshold, and speech discrimination, but not all losses can be 'corrected' with a hearing aid. Binaural (stereophonic) devices are psychoacoustically superior to monaural devices; however, behavioral and personality changes in older patients often create problems of adaptation to the binaural aid. These changes may also affect the fitting of an aid and the patient's ability to learn to use it. Some practical suggestions are offered on the evaluation of hearing aids and it is emphasized that adequate orientation and counseling are typically required if hearing aid treatment is to be successful in presbyacusis.

Binaural hearing aids: are they dangerous for children?

We report a case in which a child suffered apparently permanent damage to residual hearing due to use of a powerful hearing aid. After review of the literature on damage to residual hearing by powerful hearing aids, we suggest that due caution should be observed in the prescription and monitoring of hearing aid usage for hearing-impaired children. Uncritical advocacy of powerful binaural aids is challenged as a potentially dangerous practice.

Auditory Localisation by Hearing-Impaired Persons Using Binaural In-The-Ear Hearing Aids

The directional hearing for a white noise stimulus presented in the horizontal plane was tested for 11 hearing-impaired persons. Performance with binaural in-the-ear aids was compared to monaurally aided conditions. The data indicate that hearing-impaired subjects localise better with binaural aids. Also, presentation level is an important variable when considering monaural performance because at the higher intensities sufficient sound may enter the unaided ear to yield some binaural effects, i.e., the condition ceases to be a monaural one. Although further investigation is required, it is concluded that a procedure to measure localisation performance is important as a means for deciding whether binaural aids have been satisfactorily fitted.

Localisation of Sound with Binaural Body-Worn Hearing Aids

In a series of studies it was found that localisation of sound with binaural body-worn hearing aids was far superior to localisation with monaural body-worn aids. This was demonstrated with four severely deaf and four normal hearing subjects. Optimum localisation was achieved when the microphones of the two aids were separated by a distance of 7 to 10 inches and there was limited evidence that a separation of 8 or 9 inches is ideal. The optimum separation for localising sounds in the horizontal plane did not appear to be influenced by stimulus frequency or whether the sound was presented from behind or in front of subject. For the normal hearing subjects localisation with binaural body-worn aids was equal to localisation with binaural ear-level aids but inferior to unaided binaural localisation. For the hearing-impaired subjects aided and unaided localisation was equivalent.

Four Years’ Use of the Binaural Sensory Aid

After using the binaural sensory aid in conjunction with the long cane for years, the writer feels that his orientation and mobility have improved, that he experiences less stress and is therefore more willing to cope with travel situations he would previously have avoided, and that he has developed to some extent the ability to interpret the device's signals (to determine what object causes a particular auditory signal). He believes that a new model of the aid, Mark II, currently undergoing field tests, is superior to the various models of Mark I and that the binaural sensory aid, while not the perfect solution to all the mobility problems of blind people, is a successful mobility aid and environmental sensor.

A sonar aid to enhance spatial perception of the blind: engineering design and evaluation

The design of an air sonar device with a new form of binaural display is described which aids the blind in perceiving their environment. Some of the limitations of knowledge of human perception and the influence this has on a specification for the device are discussed. Inherent limitations in the binaural aid both in terms of technology development and performance are also explained. The paper described what is expected of the man-machine control system in a mobility setting and discusses the technique of evaluating a manmachinesystem so as to assess the machine performance.

The Sonic Glasses Evaluated

A précis of the findings from two questionnaires 169 items for the 94 users of the aid, 88 for the 21 trainers) to evaluate the ultrasonic binaural sensory aid for the blind, a mobility and orientation device invented by the author. The results, summarized in three lengthy tables, indicate that 88 percent of the users found the device useful and that only 20 percent of the trainers thought that their own training was inadequate.

Hearing Aid Distribution in Denmark

Denmark has a population of 4.9 mill. and about 2,5% are in need of audiological treatment. In the last year 13 audiology clinics have provided about 19.000 patients with 27.000 hearing aids, 8000 received binaural aids. The complete audiological examination, the fitting of one or two hearing aids and the pedagogical aftercare is free of charge for any Danish citizen regardless of age, income and fortune. The cost per person amounts to 200 dollars which corresponds to 4–5 days stay in a public hospital. If necessary the patients may ask for another treatment after a period of 5 years. In one year only 18% (13.500) of the hearing aids in use in the Copenhagen district were in need of a repair.Knapt 2 1/2% af befolkningen behover audiologisk behandling, der ydes gennem 13 audiologiske klinikker, hvor der i aret 1969/70 blev behandlet ca. 19.000 patienter med ialt 27.000 horeapparater. Principielt far alle born udleveret binaurale horeapparater, og det samme gœlder fra 1963 for voksne, for sa vidt de er fysi...

Hearing Aids: Uniform and Selective: Monaural, Diotic and Binaural; Air and Bone Conduction

Extensive articulation tests with laboratory equipment on an individual with a marked, primarily-conductive impairment have shown that for such an impairment for equal levels above threshold: (1) An amplifier prescribed according to the “most comfortable equal loudness curve” is superior to one prescribed according to a “most comfortable” curve, which in turn is better than a uniform amplifier; (2) Bone conduction is more satisfactory than air conduction if a high pass filter with cut-off frequency of 350 cycles is used in conjunction with the bone receiver; (3) Air and bone conduction together are superior to either alone; (4) When air conduction is used, frequencies up to 350 cycles and above 6500 cycles may be cut off without appreciably affecting the articulation. (Similar tests on an individual with monaural high frequency impairment have shown that low frequencies up to 350 cycles can be eliminated for either ear without markedly affecting the articulation.) Further tests with wearable vacuum tube aids on the individual with conductive impairment, have shown (1) the superiority of a binaural aid over a monaural aid, and the equivalence in articulation of a monaural and a diotic aid; (2) approximate equivalence of bone and air conduction, with crystal units being used in each case.