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Biomedical subjects

J Kiessling

Publications and source records attributed to J Kiessling.

At least 19 recordsLinked to original sources
PubMed1994

[Loudness scaling. A procedure for quantitative recruitment detection].

Direct loudness scaling has been known as an audiological tool for about four decades. Although numerous publications have shown its clinical importance, loudness scaling has not been used in audiology and hearing aid fitting until now. This might be due to the lack of audiometers equipped with loudness scaling devices as well as missing evidence for its clinical applicability. In this study normal data for a single-step direct scaling procedure were established and loudness determinations of 105 patients with sensorineural hearing losses collected. The results show that normal level loudness functions exhibit very similar shapes for narrow band stimulation in the frequency range of 500 to 4000 Hz. However, loudness scaling is affected by the gender of the subjects: females scale systematically louder than do males. In hearing-impaired subjects the slopes of the level loudness functions tend to decrease with increasing hearing loss, indicating negative recruitment. This holds particularly true in the high-frequency range, e.g. at 4000 Hz. Our long-term experience with single-step direct loudness scaling has proven its clinical feasibility in typical patients of an audiology unit. Loudness scaling will prove useful for the localization of hearing impairments, as it can be employed as a quantitative indicator of recruitment without any restrictive preconditions. In addition, it allows the evaluation of hearing aids and cochlear implants by frequency-specific gain measurement.

Audiometry, Pure-Tone↗
PubMed1993

Comparison of a programmable 3-channel compression hearing system with single-channel AGC instruments.

A commercially available programmable BTE hearing aid with 3-channel AGC (Siemens, Triton 3000) was compared to the subjects' own single-channel compression aids in a group of experienced hearing aid wearers. Two cross-over frequencies, three AGC onset levels, and three channel amplifications were programmable. The maximum output level was controlled by conventional peak clipping. The frequency response of the multichannel system was matched to the individuals' own aids which had been fitted in the two years prior to this study. Frequency response shaping was accomplished by real ear measurement monitoring. The performance of the hearing instruments was measured by (1) speech audiometry in noise and (2) subjective judgement of sound quality and speech intelligibility. Speech recognition was tested using rhyme test material in noise in a group of 10 subjects with sloping high-frequency hearing loss as well as in a group of 16 individuals with nearly flat audiograms. In both subgroups speech recognition scores (S/N: -5 to 15 dB) were 7 to 20% higher for the 3-channel AGC device compared to the single-channel AGC instruments. This finding is equivalent to an improvement of the S/N ratio of about 7 dB for the user. The results of the subjective judgements were similar for both subgroups. Sound quality and speech intelligibility were mostly rated as "very good" or "good" on a 5-point-scale. The subjects were also asked to compare the performance of their own hearing aids with the 3-channel AGC instrument; the latter generally turned out to be preferable.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1991

Clinical evaluation of a programmable three-channel automatic gain control amplification system.

This paper reports on the clinical evaluation of a commercially available head-worn programmable 3-channel automatic gain control (AGC) hearing instrument (Siemens, Triton 3000). A preliminary fitting procedure is developed for the 3-channel AGC amplification system, which is compared by 26 experienced hearing instrument wearers with their own single-channel AGC instruments. The benefits of both amplification systems are assessed by speech audiometry at different signal-to-noise ratios utilizing German rhyme test speech material. In addition, subjective judgements concerning sound quality, speech intelligibility and comparison with the subject's own instrument are evaluated. The results indicate that the multichannel compression instrument is superior to single-channel aids in competitive speech situations. If the 3-channel AGC instrument is used as an automatic noise reduction system in patients requiring a certain amount of low-frequency gain, a markedly better speech recognition can be achieved compared to the subject's personal aids.

Audiometry, Speech↗
PubMed1988

[The status of hearing aid technology from the audiologic viewpoint].

Although hearing aid technology has made considerable progress in the past, some important audiological demands are still unfulfilled. In particular, speech perception in noisy conditions must be improved. Traditional approaches to this fundamental problem, e.g. base cut, open mould fitting, horn equipped ear moulds, external receivers, in the ear hearing aids, directional microphones and audio-input, are discussed, as well as modern concepts of automatic signal processing to improve signal-to-noise (S/N) ratio. The results of a study of speech discrimination with dual channel hearing aids with AGC in the low frequency channel reveal efficient noise reduction in specific S/N situations. However, in the USA self-adaptive noise filter systems in head-worn hearing aids, have proven to be inadequate using the present set of processing parameters. Multichannel and digital signal processing introduce additional unsolved problems into hearing aid fitting.

Acoustics↗
PubMed1985

[Initial experiences with compact disc recording of the Freiburg Speech Test].

Speech audiometric results of 45 sensorineural hearing impairments (mean hearing loss in Fig. 1) are compared for magnetic tape and compact-disc reproduction. In both cases the standardised Freiburg Test (DIN 45 621) is used. As a result mean speech hearing loss determined by compact disc application (32 +/- 15 dB) is in good agreement with the value for magnetic tape use (29 +/- 15 dB). This finding is confirmed by linear regression analysis (Fig. 2). Even mean discrimination scores for monosyllables are nearly the same up to 100 dB for compact-disc as well as magnetic tape recording (Fig. 3). At higher speech levels above 100 dB magnetic tape results show insignificant (p = 0.05) lower scores than compact disc use. The "total word discrimination", defined as the sum of intelligibility scores at 60, 80 and 100 dB, is highly correlated using magnetic tape and digital recorded speech material (Fig. 4). The same holds for percentage hearing loss determined after Boenninghaus and Röser (1973) as shown in Fig. 5. If the compact-disc version of the Freiburg Speech Test will prove its worth in an representative group of subjects, it can be recommended to stabilise reproduction quality and to shorten the duration of examination until new speech audiometric tests that meet actual requirements are developed and standardised.

Audiometry, Speech↗
PubMed1984

[The value of brain-stem audiometry in the selection of hearing aids].

A procedure of hearing aid evaluation by brainstem-evoked response audiometry (BERA) is described. The vailidty of the method is tested with regard to amplitude scattering (51 subjects) and by comparison of hearing aid parameters determined by speech audiometry (205 subjects) respectively by BERA (50 subjects). The results indicate that the influence of intra-individual amplitude variation on the reliability of the procedure is of minor importance only. Comparisons of gain and compression requirement determined by speech audiometry, respectively by BERA, show good agreement, proving the clinical importance and validity of hearing aid selection by BERA. Compression factors of available hearing aids, however, are poorly correlated with estimated compression requirements: only 22% of the hearing aids meet the requirements of about 80% of the subjects.

Audiometry↗
PubMed1983

Far-field cochlear microphonics in man and their relation to cochlear integrity.

Far-field cochlear microphonics (CM) in man have been measured as a function of frequency by phase-sensitive detection. CM amplitude, dispersion and input-output functions vary periodically with frequency and exhibit certain frequency windows, where responses are approximately frequency specific, in contrast to the commonly accepted model of basal turn CM generators as main sources. Pathological cochleae show abnormal amplitude and phase functions. The results offer new diagnostic possibilities, because haircell function can be evaluated by a routine non-invasive procedure down to the low frequency speech range.

Audiometry, Evoked Response↗
PubMed1983

Clinical experience in hearing-aid adjustment by means of BER amplitudes.

Assuming that brain-stem-evoked response (BER) amplitudes are correlated with actual loudness, the dynamic range of individual hearing can be determined by means of normal and pathologic amplitude characteristics. This permits an estimation of gain requirement and compression factor in hearing-aid evaluation. Clinical importance and validity of the procedure is investigated in a group of 59 children with impaired hearing. The method yields reasonable values of hearing-aid parameters, which are comparable with those usually obtained by speech audiometry.

Audiometry↗
PubMed1982

Hearing aid selection by brainstem audiometry.

Hearing aid selection and adjustment by means of brainstem audiometry was tested in 29 hearing impaired children. A projection procedure is introduced which employs normal and pathological intensity-amplitude functions. This method enables determination of some basic properties of appropriate hearing aids, such as average gain, type of compression, compression factor and onset level. Hearing aid evaluation is discussed for two examples of conductive and sensorineural impairment.

Adult↗
PubMed1982

[Effect of nitrous oxide inhalation anesthesia on sero-mucous secretions of the tympanum].

It is known that nitrous oxide anaesthesia results in an increase of the middle ear pressure. The aim of this project was to find out, if an increase of the middle ear pressure due to high concentration of nitrous oxide could lead to evacuation of the seromucoid secretion through the Eustachian tube. In 37 children (64 ears) scheduled for myringotomy, tympanograms were performed immediately before and during anaesthesia, the middle ear fluid was confirmed by myringotomy and, if any, sucked out. Both the comparison of the tympanograms prior and during the anaesthesia and the results of myringotomy led to a conclusion, that, in general, nitrous oxide anaesthesia induces no evacuation of middle ear fluid via the Eustachian tube.

Acoustic Impedance Tests↗
PubMed1981

Frequency-following potentials in man by lock-in technique.

Frequency-following responses (FFR) from continuous tone stimulation were investigated by lock-in analysis. The technique is superior to conventional tone-burst stimulation, because it allows continuous registration of the response parameters with sweeping frequency. The scalp recorded FFR consists of at least two components separable from each other by their phase/frequency relationship. The microphonic component that dominates in ipsilateral records shows latencies of about 0.5 msec with negligible dispersion and must therefore originate in the basal cochlear turn. The neural component exhibits considerable dispersion, reflecting the travelling wave delay up to the region of best frequency. These long cochlear time delays are consistent with an apical FFR origin, and brain stem sources of the continuous tone response appear to be questionable. The present FFR analysis technique opens up a very direct and comprehensive way to assess the integrity of the entire inner ear for high frequency basal and low frequency apical cochlear regions as well.

Acoustic Stimulation↗
PubMed1981

[Highpass filtering of auditory evoked brain stem potentials (author's transl)].

Twenty ears of normal-hearing subjects are investigated as to the influence of highpass filtering on latency, amplitude, and shape of auditory evoked brain stem potentials. For this purpose, three different Bessel-filters (steepness 24 dB/octave) with lower cut-off frequencies at 100, 200, and 300 Hz (3-dB down points) and an upper cut-off frequency at 3 kHz are used. Spectral composition of brain stem potentials is analyzed by digital filtering based on Fast Fourier Transformation. Results show decreasing latency and amplitude of the negative wave between Jewett V and VI with increasing lower cut-off frequency. With higher edge frequencies we find attenuation of wave V relative to wave IV amplitudes. For that reason we must assume that an essential part of brain stem activity is located below 300 Hz. In our experience moderate highpass filtering seems to be useful in neurological cases to eliminate low frequency components of the signal. In that way potentials I -- V are easy to be identified and interpeak latencies can be determined without any problems. For objective threshold determination, however, brain stem potentials should be derived preferably with broadband filter settings to improve correlation of tone audiometric hearing loss (at about 3 kHz) and brain stem response threshold. A filter set with different lower cut-off frequencies has proved to be really useful in routine work. However, it must by taken into account that highpass filtering means an alteration of the original response in any case.

Audiometry↗
PubMed1980

Input-output function of the acoustic reflex and objective hearing aid evaluation.

Hearing aid evaluation procedures should mainly consider hearing properties in the most comfortable loudness intensity range. This applies to both subjective and objective methods. With regard to this aspect, input-output characteristics of the acoustic reflex were investigated for speech noise and narrow-band noise (0.5, 1, 2 and 4 kHz) stimulation. In these terms, hearing aid evaluation can be understood as an approximation of pathological input-output functions to the normal range by suitable hearing aids. After normal input-output characteristics have been established, we report on first experiences with this fitting procedure. Frequency-specific elicitation of the stapedial reflex with and without hearing aid enables a compensation for hearing impairment in accordance with frequency-dependent dynamic properties.

Acoustic Impedance Tests↗
PubMed1980

[Tympanometry when decomposing the sound conduction apparatus (author's transl)].

It is reported on tympanometric investigations of 21 postmortem temporal bones. Tympanograms (220 Hz probe tone) show increasing compliance maxima with stepwise destruction of the sound conduction apparatus. After sucking off peri and endolymph, opening the tympanic cavity and cutting the middle ear muscles compliance increments, however, are rather small and we get tympanograms within normal range. Only when cutting incus-stapes-connection tympanograms exhibit abnormal high compliance maxima. Therefore the value of tympanometry with 220 Hz probe tone should not be overestimated for clinical middle ear diagnosis.

Acoustic Impedance Tests↗
PubMed1980

[Masking of tinnitus aurium by maskers and hearing aids (author's transl)].

Several studies in the U.S.A. have shown that tinnitus aurium can be reduced by use of maskers or hearing aids. Contrary to the noise of tinnitus, that produced by the masker or hearing aid is localised outside the ear and is less troublesome to most people. Comparing the benefits of both methods (masker against hearing aid) a study of 108 patients with tinnitus aurium was carried out. A group of 58 suitable patients were provided either with tinnitus maskers or with hearing aids for a few weeks. Satisfactory masking was achieved in about 50 per cent of those using hearing aids whereas this was achieved in only 10 per cent using tinnitus maskers.

Evaluation Studies as Topic↗
PubMed1979

[On the interpretation of Békésy audiograms (author's transl)].

A group of 112 subjects with sensorineural hearing loss was checked by an audiological test battery consisting of: pure tone audiometry, SISI Test, tone decay test and fixed frequency Békésy audiometry. Classification of Békésy tracings by two audiologists showes good agreement when introducing a hybrid type I/II, which completes Jerger's classification system of types I--IV. The results of our investigation exhibit no significant differences of manual pure tone threshold and automatic tracing contrary to some other authors. Finally the correlation of diagnosis and type of Békésy audiogram is discussed.

Audiometry↗
PubMed1979

[The value of SISI test for audiological examination (author's transl)].

The reliability of SISI Test for audiological evaluation of hearing impairment is investigated basing on audiometric findings of 604 subjects. In addition to the dependence of SISI scores on the age of the subjects the influence of sound pressure level and frequency is discussed. Comparing SISI results with those of other differential diagnostic tests we find that SISI test tends to indicate haircell lesions even though other tests exhibit a different site of the lesion. Particularly in cases of uncertain, complex hearing impairments (noise plus other causes) SISI test frequently shows false-positive results. Therefore SISI scores should be interpreted carefully especially with regard to legal examination of noise induced hearing impairment.

Adult↗