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PubMed1986

[The promontory test and electrocochleography with reference to indications for cochlear implant].

A successful cochlear implant demands a functioning auditory nerve. A subjective and qualitative recording can be obtained by promontory testing (PT) whereas cochlear microphonics (CM) give information about the status of the hair-cells in the inner ear. The results of both tests together show different patterns: in sensory deafness in which a cochlear implant is indicated, no CM and no compound action potentials (CAP) can be obtained, whereas the patient reports hearing sensations (PT positive) in response to promontory testing. Deafness caused by lesions close to the second neurone of the auditory pathways can be localized by preserved CM and CAP, but there is no response to promontory testing. A ganglionic deafness ie. of the first neurone can be distinguished by preserved CM, absent CAP and a negative PT. The combined results of electrocochleography and promontory testing help in deciding whether a cochlear implant is indicated, and in localising the origin of the deafness, eg. neural or sensorineural. The possible results are illustrated by examples.

Adult↗
PubMed1986

Extracochlear implants.

A unichannel extracochlear implant designed and made in our laboratory was tried on several patients. Results to date are very similar in all cases. Very rudimentary auditory information is provided, which can help totally deaf patients.

Cochlear Implants↗
PubMed1985

Auditory adaptation: notes on power and parabolic curve fitting across intensity: II.

The classic Simultaneous Dichotic Loudness Balance (SDLB) procedure for the study of auditory adaptation was used by Weiler and Hood (1977) in a successful test of a model for predicting adaptation in db at intensities above the initial baseline values, using a linear approximation across levels. When Balzer et al (Brit. J. Audiol., 1984, 18, 49-50) fitted curves for simple baseline adaptation data from four studies based on SDLB data, they reported good fits for the Gompertz technique and for a parabolic formula, but did not test the relative goodness of fit for the linear formula, nor for power approximations as Stevens (1975) might have proposed. The present study makes use of the data used by Balzer et al but examines a linear fit as well as two approximations to Stevens' power law. The present finding that the linear approximation is the least efficient examined would suggest that the Weiler and Hood model should be re-examined to determine the degree to which the model can be improved by use of a curvilinear baseline fit. In addition, it might be noted that the curvilinear formulae, of necessity, involve two or more stages. It is the the current effort of this laboratory to determine whether this reflects a multifactor basis to the classic SDLB adaptation, as well as results from other adaptation techniques.

Adaptation, Physiological↗
PubMed1985

Monaural and binaural adaptation in sequence: SDLB analogue?

Magnitude estimates (M.E.) of loudness of a 1-kc/s tone in the R ear at 60 db SPL were required over three 3-phase sessions from 15 normal-hearing young adults. The initial tone in the session was arbitrarily assigned a value of "60 units" in instructions to the S. The session was arranged to be analogous to that commonly used in Simultaneous Dichotic Loudness Balancing (SDLB). In a baseline Phase I in any of 3 sessions both ears received identical, simultaneous, intermittent stimulation. In each session, one of 3 duty cycles (randomized) were used (all on-times of .5 sec, off-times of .5, 4.5, or 24.5 sec). An M.E. judgment was requested every 10 sec for just over 1 min. Then immediately in Phase II the L ear received nothing while the R ear received continuous stimulation at 60 db SPL for 7 min, with M.E. Judgements requested every 10 sec during Min 1 and every min thereafter. Then in Phase III the R ear continued to receive continuous stimulation at 60 db SPL for 1 min while in the contralateral ear the condition of Phase I was re-introduced. M.E. loudness judgements for the R ear were requested as in Phase I. During Phase I there was, as expected, no loudness adaptation. During the adapting Phase II, M.E. group values declined progressively and significantly, but without significant differences among duty cycles. M.E. values in Phase III continued to decline significantly even though the contralateral ear was being given intermittent stimulation (irrespective of duty cycle). Previous studies had found that, for most listeners, M.E. loudness adaptation does not occur when the continuous stimulation is presented by itself. As far as is known, the present study is the first M.E. loudness adaptation study to present binaural intermittent stimulation before the continuous monaural stimulus. It is suggested that the redundancy of the continuous monaural stimulation, in comparison with the similar intermittent stimulus, is associated with the diminution of loudness.

Adaptation, Physiological↗
PubMed1985

Hearing in two cricetid rodents: wood rat (Neotoma floridana) and grasshopper mouse (Onychomys leucogaster).

The audiograms of two wood rats and three grasshopper mice were determined with a conditioned avoidance procedure. The wood rats were able to hear tones from 940 Hz to 56 kHz at a level of 60 dB (SPL), with their best sensitivity of -3 dB occurring at 8 kHz. The hearing of the grasshopper mice ranged from 1.85 kHz to 69 kHz at 60 dB (SPL), with their best sensitivity of 9 dB also occurring at 8 kHz. These results support the relation between interaural distance and high-frequency hearing and between high- and low-frequency hearing. The inability of the grasshopper mouse to hear low frequencies as well as other desert rodents such as kangaroo rats and gerbils demonstrates that not all rodents found in deserts have developed good low-frequency hearing. The degree to which general and specific selective pressures have played a role in the evolution of rodent hearing is discussed.

Animals↗
PubMed1986

Normal intelligibility functions for the Auditec CID W-22 test at 30% and 60% time-compression.

Time-compressed speech has been used to identify the site of central auditory disorders and auditory processing problems. Some authors suggest that the determination of audiometric normalcy should include satisfactory performance on a speech intelligibility test sensitive to central auditory dysfunction, such as time-compressed speech. Before scores from patients with auditory disorders can be meaningfully interpreted, however, it is necessary to establish normal performance on standardized recordings. Thus, this study was undertaken to generate speech intelligibility functions in a normal-hearing population using the Auditec CID W-22 recordings with 30% and 60% time-compression. The 30% condition revealed a slope of 3.24% per decibel and the function approached a plateau at 35 dB sensation level (SL). The 60% condition produced a function that increased gradually at 1.8% per decibel over the 20 to 80% intelligibility range. An intelligibility score of 82% was observed at 46 dB SL where the function approached an asymptote. These functions provide a standard against which subjects with central auditory dysfunctions can be compared. The relative difficulty that normal subjects had with the 60% time-compressed speech suggests that this condition may be too difficult for some subjects with central auditory disorders.

Adult↗
PubMed1985

[Bilateral caloric long-term irrigation as a method for the differentiation of tonal tinnitus].

In 307 subjects with tinnitus aurium, the parameters frequency, loudness, and masking levels did not correlate significantly with the basic diseases. As a new possibility in differentiation between tinnitus of central or peripheral origin, bilateral caloric long-term irrigation of the ear canal is presented. Using warm water leads to an increase, cold water to a decrease in the loudness of tinnitus. Such results were found in cases of Menière's disease and noise-induced hearing loss. An explanation of this phenomenon lies in the hypothesis of tinnitus genesis established by Tonndorf.

Adult↗
PubMed1985

[Sudden deafness--on the age dependence of therapy results with reference to naftidrofuryl (Dusodril)].

The results of treatment of 100 patients with sudden sensorineural hearing loss were analysed in three age groups (under 30, 30-60, over 60 years). The basic therapy consisted of Dextran, Diazepam and Vitamins. One half of the patients in each age group was treated with Naftidrofuryl (Dusodril) too. Sudden hearing loss was more profound in the elderly patients than in the younger ones, and the hearing gain (%) decreased with increasing age. The absolute (dB) hearing gain was more or less independent of age and Dusodril, and for all patients averaged 21 dB. Only the hearing gain (%) of the 30-60 year old patients treated with Dusodril was significantly greater than that of the control group treated without Dusodril.

Adult↗
PubMed1985

[Electrophysiologic studies on the course of the adaptation phase following noise stress].

It was the aim of this study to settle the problem whether the post-stimulatory pattern of the extent of excitation (amplitude, latency) registered with the cortical evoked potentials can be verified in the recovery phase via leads from the brain stem region and cochlea. In this context electrophysiological measurements with human and animal material were performed. After a five-minute stimulation with a wide-band noise of various intensity we examined in the post-stimulation phase the specific stimulus pattern of the evoked potentials during an interval of 5 minutes with a resolution of 5 sec. We determined the change in response patterns of evoked potentials. Finally, the relevance of the results with regard to various nuclei of the auditory pathway is compared with corresponding electrophysiological measurements of the cochlear microphonics potentials, the VIII nerve compound action potential, and evoked potentials of different units of the brain stem and brain.

Animals↗
PubMedDate not supplied

The controversial relationship between loudness discomfort levels and acoustic reflex thresholds.

Controversy presently exists concerning the relationship between loudness discomfort levels (LDL's) and acoustic reflex thresholds (ART's). In this study, LDL's and ART's were obtained for two groups of ten normal-hearing adult subjects and one group of ten adult subjects with bilateral sensorineural hearing losses. The procedure involved obtaining LDL's and ART's under earphones and under sound field conditions for four different acoustic stimuli: pure tones, warble tones, spondaic words, and speech spectrum noise. One group of normal-hearing subjects and the hard-of-hearing group of subjects were given "too loud, uncomfortably loud, or annoyingly loud" LDL instructions while a second group of normal hearing subjects were instructed to respond when a sound "first starts to become uncomfortable." Results indicated that LDL's, irregardless of instructional pattern, were reported at consistently higher sound pressure levels than the ART's, for all groups of subjects. The magnitude of the differences between the LDL's and ART's varied according to LDL instrucitons, type of test stimulus, hearing sensitivity of the subjects (normal hearing or hard-of-hearing) and transducer used for stimulus presentation. The results of this study demonstrate that ART's correlate too poorly with the LDL to permit ART's to be used as an objective measure of loudness discomfort.

Acoustic Impedance Tests↗
PubMedDate not supplied

Loudness and the acoustic reflex: normal-hearing listeners.

The relationships among most comfortable listening level (MCL), loudness discomfort level, and the acoustic reflex to speech were studied on normal-hearing listeners using earphones and sound field test conditions. Recorded sentence materials were presented monaurally in quiet and, in the sound field, in the presence of 55 dB SPL cafeteria noise. The results indicate the MCL in the quiet sound field at approximately 70 dB SPL with the acoustic reflex occurring at 16 dB higher intensity. The earphone MCL was 7 dB lower than in the sound field, a finding that may reflect a real reverse in usual earphone/sound field results or simply calibration factors particular to the speakers and test room used in this study. The AR to speech seems to occur at approximately equal intensities between the MCL and LDL tested in quiet. The MCL is elevated by noise whereas the acoustic reflex remains at a constant level, indicating that no absolute relationship exists between loudness and the AR.

Acoustic Impedance Tests↗
PubMedDate not supplied

The stability of and the relation between the acoustic reflex and uncomfortable loudness levels.

Acoustic reflexes and uncomfortable loudness levels were recorded for eight normal-hearing listeners on eight separate occasions and eight listeners with sensorineural hearing impairments on three to four occasions. Frequencies tested were 500, 1000, 2000, and 4000 Hz for both measures. Neither acoustic reflexes nor uncomfortable loudness levels was found to vary significantly across sessions for either the normal or hearing impaired listeners. However, significant intensity differences were noted between acoustic reflexes and uncomfortable loudness levels, for both subject groups, and these differences were dependent upon subject and frequency.

Adult↗