Types Of Hearing Aids Research Articles

Examination of the CROS type hearing aid.

This study was designed to examine the CROS type hearing aid under a number of listening conditions, both advantageous and disadvantageous, in order to determine whether the relative merits of the instrument could be demonstrated in the laboratory. CNC word lists were presented against a background of cafeteria noise to evaluate the performance of 20 unilaterally impaired subjects under five unaided and five aided listening conditions. Speech intelligibility scores obtained under the experimental conditions were converted to deterioration scores relative to better ear discrimination in quiet. Deterioration of unaided speech scores ranged from 14% under the most favorable listening condition to 58% under the least favorable condition. Deterioration of aided scores ranged from a low of 20% to a high of 39%. The results suggest that while the CROS hearing aid enhances intelligibility under favorable use conditions, it degrades speech intelligibility in some demanding situations.

Ultrasonic welding device: Cole, J.M., US patent 3, 436, 006 (1 April 1969) (filed 22 June 1965)

1.1. The 10-g radio telemeter described permits a child at play to move about unencumbered by wires or heavy equipment.2.2. Continuous monitoring for periods up to 5 h is feasible using standard hearing aid type batteries.3.3. Electrode sway artifact and 60-c/sec interference have been virtually eliminated Muscle artifact is reduced by filters in the receiver.4.4. Either needle or disc electrodes can be used.5.5. No special receiving equipment is required. A commercially available FM tuner with minor modifications is used.6.6. Tests have shown excellent correlation between direct recordings and telemetered EEGs of normal adults.

Body Type Hearing Aids for Unilateral Hearing Losses

Body Type Hearing Aids for Unilateral Hearing Losses

Using a type of master hearing aid as an auditory trainer.

Using a type of master hearing aid as an auditory trainer.

THE ANGULAR LOCALIZATION BY USING HEARING AIDS

The investigation was carried out for the purpose of clarifying the deviation of the angular localization by using various types of hearing aids, and the relation between the microphone's position of a binaural hearing aid and its directional hearing.The procedure was performed at 9 locations on a half circle in front of the subject by means of pointing out the sound source. The subjects were normal hearing adults and various types of hearingimpaired.The results were as follows :i) The error of angular localization at each test location was shown on the deviation curves in 7 types, and the results were checked for its mechanism.ii) In cases of using the monaural hearing aid, the deviation of angular localization increased at the contralateral side of the hearing aid. In cases of the binaural hearing aid, it increased at bolh lateral sidesiii) The acuity of directional hearing by using the binaural hearing aid is maintained much better than that of the monaur al aid. In cases of binaural hearing aids, it is advisable for the microphones to be worn on the bilateral temporal parts of the head, because of the important role of the shadow effect of the head for directional hearing by using the hearing aid.iv) In cases of the Y-cord type hearing aid, the directional hearing acuity was completely disturbed.v) The efficiency of the hearing aid for the directional hearing is similar to that for the binaural listening.

A subminiature radio EEG telemeter for studies of disturbed children

1. 1. The 10-g radio telemeter described permits a child at play to move about unencumbered by wires or heavy equipment. 2. 2. Continuous monitoring for periods up to 5 h is feasible using standard hearing aid type batteries. 3. 3. Electrode sway artifact and 60-c/sec interference have been virtually eliminated Muscle artifact is reduced by filters in the receiver. 4. 4. Either needle or disc electrodes can be used. 5. 5. No special receiving equipment is required. A commercially available FM tuner with minor modifications is used. 6. 6. Tests have shown excellent correlation between direct recordings and telemetered EEGs of normal adults.

A Varidirectional Condenser Microphone

This condenser microphone has a self-contained power supply and uses hearing-aid type batteries. Cable connection is by means of a conventional 2-conductor shielded cable. The microphone, already somewhat more directional than a unidirectional microphone, can be made still more directional by applying an 18-in. long tubular attachment weighing only 5 oz. Total weight of unit, including mounting and windscreen, is 1 lb 12 oz. Open-circuit output voltage at 250-ohm tap is 1.6 mv/dyne.

Research Directions

Psychophysical experiments in which sounds are conducted separately to the two ears via earphones yield a body of fairly precise information on lateralization sufficient for a variety of theoretical models—electronic and physiological. The relation between such studies and the localization of actual sources in external space remains to be worked out more completely. Comparison of the abilities to localize among different species should yield data that are ordered in some relation to the size of the head. Localizations outside the horizontal plane remain a relatively untouched area of study in which there has not been sufficient test of the one clearly suggested mechanism involving head rotation that was offered by Wallach thirteen years ago. Both head rotation and other bodily movements appear to be intimately associated with changes in localization brought about through learning. The modifiability of localization responses has been demonstrated, primarily in the horizontal plane, from the early 1900's by Young to very recent years by Held, and surely should contribute to our understanding of the native as opposed to the acquired aspects of localization. Finally, our present concepts will probably need to be expanded in order to account for that degree of localization found in one eared listeners and in users of different types of hearing aids.

American developments in miniature capacitors

Miniaturization of capacitors in America comprises a large effort and a wide variety of techniques and materials. In ceramics, major programmes directed toward reducing film thickness are approaching the 1 mil range. Thin-film studies are contributing evaporated dielectrics and the basis for anodic-film printed capacitors. A thermal oxide with excellent properties can be grown on silicon. Silicon nitride and reactively sputtered dielectrics are in the exploratory stage. Extension of solid-electrolytic capacitor designs is providing relatively large capacitance in small volume, both for the micro-module programme and as hearing-aid types. Progress is being made in realizing the intrinsic capability of organic polymers.The future holds promise of significant accomplishments both by application of ingenuity to the older materials and by realizing the potential of thin-film technology.

On the use of hearing-aid type earphones in clinical audiometry.

In a preceding article (König, 1962) it was demonstrated that the most important factors which actually limit the range of application of the different procedures normally employed in clinical audiometry are the transcranial and transtemporal leakages. The observations reported here are intended to concretize our previous theoretical considerations and to show how the use of hearing-aid type earphones may enhance the accuracy of audiometric measurements. In order to evidence the advantages of such earphones in a striking manner, the author gives a typical example of severe bilateral middle ear deafness where neither the air-conduction curves nor the bone-conduction curves could be determined correctly by means of ordinary receivers of commercially available audiometers, whereas by using hearing-aid type earphones the audiometrist was able to establish a more strictly accurate audiogram. In contrast to the maximum bone-air gap generally observed in the different audiology centres, transtympanic transmission losses as high as 90 db were recorded at certain frequencies.

Deafness

The great English lexicographer, Dr. Samuel Johnson, once wrote of deafness as the "most desperate of human calamities." With this in mind, the author has attempted an all-inclusive volume on deafness, gearing it to both professional and lay people. He has included sections on the incidence of deafness; the anatomy and physiology of the auditory system; the various types of hearing aids; conductive, perceptive, and psychogenic deafness; and an appendix which lists materials for testing deafness as well as organizations and institutions concerned with deafness. The physician should welcome this volume, not so much as a guide for himself, but rather as an informative manual on deafness for his patient. Most of the anatomical and physiological references have been kept on a plane that will be understood by the discerning layman. The more scientifically oriented reader, however, may question some of the statements made, especially with regard to the inborn

An Air Damped Artificial Mastoid

An air damped artificial mastoid has been constructed to simulate the mechanical impedance of the human mastoid. Viscoelastic substances extensively used in current mastoid designs are not employed. The instrument is virtually immune to aging effects and can be easily reproduced. The instrument is used as a laboratory standard to determine the force transmitted through the skull by bone vibrators used in clinical audiometers and bone conduction type hearing aids.

ELECTRO ACOUSTICAL CHARACTERISTIC AND ARTICULATION SCORES OF HEARING AID

The relation between electroacoustical characteristics and articulation scores of hearing aid was studied in respect with effectiveness of hearing aid. Five different types of hearing aids were classified in order of A, B, C, D and E in respect to their articulation scores of speech obtained by 40 persons of nerve deafness and 6 persons of mixed deafness. This order could be heardly found in the frequency-characteristic of out put and the harmonic distortion of the tested hearing aids. However, the results of transient distortion of the hearing aids was proved to be proportional to the order of the effectiveness of the hearing aids. Furthermore, compression amplification circuit added to the hearing aid was studied for the purpose of modifying effectiveness of the hearing aid and, its positive result could be obtained.

Masking in audiometry; further studies.

Interaural attenuation plays an important part in clinical masking tests. Attempts have been made to increase the average figure of 50 db for ordinary, air conduction receivers to higher insulation by using an ear canal insert which greatly reduces the area under the sound.Two types of inserts were used: one, made of plastic and fitted over the earphone, led the tone via a perforated tip into the meatus. The other employed a microphone of hearing-aid type, leading the tone to the ear canal by a plastic tube with soft rubber point. Interaural attenuation was measured by the masking method.The hearing-aid type plastic tube in the meatus was the better of the two, providing 70 db insulation. It proved to be easy to handle and convenient to use.The rules governing the use of masking in audiometry are discussed briefly. For clinical routine use, white noise is preferred to bands of noise.

Hearing aid evaluation.

Although the individual hearing aids from a single day's production may be of a uniform appearance, their amplifying capacities may very well differ. As physicians we are accustomed to trusting our co-workers, e. g., the pharmacists, expecting specific types of tablets to contain identical quantities of a certain drug. But a similar standard cannot be applied in the case of hearing aids. The individual hearing aid is composed of numerous components, all of which may deviate in some respect, thus causing final discrepancies. In many countries the official authorization of a type of hearing aid is based on some few selected specimens, a procedure which, according to our experience, seems rather insufficient, since it is not very difficult for any manufacturer to select five almost uniform hearing aids to be submitted for authorization. Since October, 1951, the Copenhagen Hearing Center has practiced a current control, by means of an "artificial

Acoustic Attenuation of Earphone-Noise Shield Combinations

The sound exclusion properties (acoustic attenuation) of various combinations of earphones and noise shields were determined by the threshold-shift method. The earphones included dynamic earphones in donut cushions and hearing aid type receivers with individually molded inserts. The noise shields included conventional earplugs, muffs, and a noise exclusion helmet. Test sounds were octave bands of noise at each of the seven octaves starting with 75 to 150 cps and ending with 4800 to 9600 cps. The order of merit for exclusion of external noise, listing the best combination first, is (1) the helmet with insert-type phones, (2) the helmet with dynamic earphones, (3) the dynamic earphones over earplugs, and (4) the muffs over insert-type phones. The best combination provided 9 db attenuation in the 75–150 cps octave, 18 db in the 150–300 cps octave, 24 db in the 300–600 cps octave, 34 db in the 600–1200 cps octave, 44 db in the 1200–2400 cps octave, 54 db in the 2400–4800 cps octave, and 48 db in the 4800–9600 cps octave.

Non-Linear Distortion in Hearing Aids

Measurements of non-linear distortion were made on a typical hearing aid by three standard methods. These methods are: (1) the harmonic method, (2) the intermodulation method that evaluates distortion in terms of the modulation of a high frequency tone by a low frequency tone, and (3) the difference-frequency intermodulation method, which evaluates distortion in terms of the amplitude of the difference tones produced by intermodulation of two applied tones. The measurements and analysis of results on the basis of masking effects indicate that the difference-frequency intermodulation test is the most significant test for non-linear distortion in hearing aids.

Tentative Code for Measurement of Performance of Hearing Aids

These specifications for methods of measurement of hearing aids were drawn up by a technical committee organized by the American Hearing Aid Association, including engineering representatives from most of the larger manufacturers of hearing aids as well as technical representatives from non-commercial groups who have been working in this field. It is believed that these specifications represent the best of present practice, although additions may be made later to cover further material such as methods of applying correction factors for the baffle effect of the body of the wearer, for the difference between the pressure and the free field characteristics of the ear, and for possible leakage of sound between the ear and the ear insert, as well as standardized methods of measurement of instruments with bone conduction receivers and of carbon type hearing aids. Since sufficient information is not yet available to reach definite conclusions on these points, the code is offered in its present form for consideration by those interested in this subject.