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PubMedDate not supplied

A slow brain stem response for low-frequency audiometry.

Proper choices of stimuli and of brain stem electric responses allow us to estimate peripheral auditory thresholds at 500, 1 000, 2 000 and 4 000 Hz with an accuracy of about +/- 10 dB. With the help of sedation (secobarbital), such audiograms may be obtained from each ear of a child of any age in a single session. Tone pips (filtered clicks) or very brief tone bursts give a frequency selectivity that is clinically adequate. The rise time must be adjusted to the center frequency. A rise time of two periods with a plateau from zero to one period gives a good compromise between frequency specificity and a synchronous neural discharge. The best threshold indicator for tone pips of 2 000 Hz or higher (or unfiltered clicks) is P6 (Jewett V). At 60 dB nHL its latency is 6.0-7.0 ms (for children of 1 year or older), but near threshold it is 8.0-9.5 ms. An input pass-band of 140-3 000 Hz is appropriate. The best threshold indicator at 500 or 1 000 Hz is a nearly neglected slower wave with a scalp-negative crest at about 10 ms following a 60-dB click. Latency is 15 ms following a 500-Hz tone pip at 15 dB SL. We call this wave "slow negative (ten)" or SN10. To see it well a wider input pass-band such as 40-3 000 Hz is needed. SN10 is usually obscured by P6 or by frequency-following response at stimulus levels above 35 dB SL. The details are given of a clinical routine that allows the determination (+/- 10 dB) of 8 threshold endpoints within about 80 min. Several precautions and limitations are discussed, and also the origin of the SN10 wave.

Audiometry↗
PubMed1984

Frequency selectivity and thresholds of brief stimuli suitable for electric response audiometry.

Auditory evoked potentials are nearly all on-effects and the 'effective stimuli' for them are necessarily brief. Their frequency specificity is therefore limited, especially for the brainstem responses, because of the well-known trade-off between duration and frequency specificity. Brainstem responses are of special interest because they are unchanged in the sleep-like sedation that is required for difficult-to-test children. The middle-latency responses do not meet this requirement. Two patterns of tone burst that are appropriate and promising for the slow cortical potentials and for brainstem potentials, respectively, have rise and fall times of 2 periods of the modulated tone and plateaus of 10 (or 7) periods and 1 period, respectively. Their behavioral thresholds are nearly insensitive to difference in repetition rate between 4 and 40 stimuli/s. Their peak equivalent SPL threshold values at 500, 1 000, 2 000 and 4 000 Hz have been determined for 16 otologically normal ears. Using these reference levels, audiograms have been obtained for subjects with impaired hearing. The audiograms for 'flat' hearing losses do not differ significantly from the corresponding conventional pure-tone audiograms. The slopes for steep high-frequency hearing losses are underestimated, however, particularly with the brief (2-1-2) pattern. Nevertheless, the 2-1-2 pattern appears to be close to the best possible compromise.

Acoustic Stimulation↗
PubMedDate not supplied

Speech audiometry in noise-exposed workers: the SRT-PTA relationship revisited.

The speech recognition threshold (SRT) is believed to be related primarily to the pure-tone average (PTA) and the steepness of the hearing loss. However, there are indications that it may also be influenced by perceptual or cognitive-linguistic factors, or both, such as meaningfulness of the speech stimuli. The purpose of the present study was to ascertain the correspondence between SRT and PTA in noise-exposed workers with various degrees of speech recognition threshold shift in noise. To this end, a total of 807 SRTs and PTAs collected from fluent speakers of Quebec French noise-exposed workers were compared. Measurements of context effects on speech recognition were taken based on a general hypothesis that they should be facilitating phoneme or word restoration in conditions of high stimulus uncertainty as present in SRT assessment, thus acting to confound the SRT PTA relationship. Using principal components analysis, we found a significant effect not only of low-frequency hearing sensitivity but language context effects on SRT. After a correction was introduced to partial out these linguistic context effects, correlations between SRT and PTA increased but they were lower than predicted. In a related treatment analysis, we found a large number of observations (230 out of 807) where SRTs were more sensitive than PTAs by a factor of 8 to 16 dB. This was the case even though correlations between the two measurements were within the range commonly advocated in the field of clinical audiology (0.85-0.95). This was interpreted as a sign of phonological and lexical context effects on the speech recognition task actually used by individual subjects to facilitate speech understanding, to the point perhaps of making it as simple as the detection of pure tones.

Adult↗
PubMed1979

Comparison of ascending and bracketing methods in pure tone audiometry. A multi-laboratory study.

Four laboratories participated in this study to compare ascending and bracketing methods in manual determination of hearing thresholds using attenuators with 5 dB step. In all, 214 ears were measured. No significant difference was found between mean thresholds obtained with the two methods in the frequency range 0.5--6 kHz; the four-laboratory, six-frequency grand mean difference was -0.31 dB. The variability among subjects also remained essentially the same for the two methods. However, the bracketing method required a significantly longer test time than the ascending method.

Adolescent↗
PubMed1981

Reference values and characteristics of brain stem audiometry in neonates and children.

ABR (Auditory Brainstem Response) delivering the acoustic stimulus both through a headphone (PHN) and in free field (FF), have been recorded in 59 "normal" children divided into four age-related groups: (1) 22 children born at a gestational age ranging between the 36th and the 41st week; (2) 12 with ages ranging from 1 to 6 months; (3) 15 with ages ranging from 6 to 12 months; (4) 10 with ages ranging from 12 to 36 months. Peak latency values obtained with FF technique have been corrected by calculating the delay due to the distance between the loudspeaker and the tested ears (2.04 ms). When using this correction, no statistically significant differences were found between latency values of peaks JI and JV recorded using the two technique. While JI latency values of various groups do not differ significantly, groups 2--and especially group 1--JV latency values are statistically different from those of the 3rd and 4th group. This observation was confirmed by JV--JI interval values. JV wave in neonates (group 1), using PHN technique, is detectable at 60 dB p.e. SPL (82%) while in all other groups at 60 dB this wave is clearly detectable in all children (100%). Using FF technique, JV wave is still visible at 60 dB in 78% of the neonates (group 1) and in almost all children of the other groups. Considering ABR waveform, using PHN technique, in the first two groups only three waves are visible and the first one disappears at about 80 dB, while the typical 4--5 waves of normal adult tracings are detectable since 8--12 months of age. FF tracings instead show three peaks in all groups, the first (JI) being less evident when compared with the one obtained using PHN technique. JV amplitude values observed in FF are higher than those obtained delivering the stimulus through the headphone.

Acoustic Stimulation↗
PubMed1983

High-pass and notch noise masking in suprathreshold brainstem response audiometry.

The combination of suprathreshold tone-bursts with frequency of 0.5, 1 or 2 kHz and ipsilateral high-pass (HP) or notch noise masking has been studied in 52 adults referred for otoneurological examination on account of unilateral or asymmetric high-frequency hearing loss. Wave V latency changes are similar for both HP and notch noise masking and, in accordance with cochlear tonotopicity, are greater for the lower stimulus frequencies. Results are, however, not always conclusive with either technique, and response identification is problematical at 0.5 kHz. The less demanding HP masking technique is considered the method of choice since possible influence from the stapedius reflex is minimal and a better signal-noise ratio obtained.

Acoustic Stimulation↗
PubMed1984

'Quasi free-field' audiometry: proposal for a modified transducer system.

The authors studied a group of 13 young adults by using high-frequency techniques in 'quasi free-field' conditions, as suggested by Osterhammel, and comparing the results with those obtained by means of an original method suggested by the present study group. The data relative to this last-mentioned technique confirmed it as being valid on the grounds of test-retest findings and standard deviation. It is concluded that both methods are equally effective for the study of the physiology of the ear, but that the present method is less practical from the clinical point of view.

Adult↗
PubMed1991

High-frequency audiometry. Response characteristics of the KH70 vibrator.

Various response characteristics of the Präcitronic KH70 bone vibrator have been investigated in the frequency range 0.25 through 16 kHz. Masked threshold reproducibility is satisfactory throughout the frequency range. An occlusion effect is present only at frequencies at and below 1 kHz. Stimulus perception lateralizes to the occluded ear through 1 kHz and less consistently at successively higher frequencies. The KH70 does not satisfy the IEC 645 (1979) criterion for acoustic radiation for frequencies below 6 kHz, especially at the intermediate frequencies of 0.5, 1 and 2 kHz. With the restrictions inherent in the occlusion effect, this does not, however, interfere with threshold determination. The vibrator would thus seem suitable for clinical use through 16 kHz.

Adult↗
PubMed1983

Towards fully objective evoked response audiometry.

The amplitude spectra of the auditory brainstem potentials evoked by free-field stimuli revealed significant differences from the corresponding spectra of pre-stimulus records. This was most marked for low order harmonics and in response to high intensity stimuli. In general, however, the shape of the amplitude spectrum for pre-stimulus and post-stimulus epochs was similar and the magnitude of the differences between corresponding harmonics became progressively smaller as stimulus intensity was reduced. Given that the spectrum of each coherent grand average is a function of the amplitude and phase spectra of the response ensemble, these were separately examined. Ensemble mean amplitude of individual harmonics diminished with stimulus intensity while their phases became progressively less aggregated. Phase standard deviation, used as a parameter of this aggregation, was found to change more systemically with stimulus intensity than ensemble mean amplitude. Phase standard deviation values for threshold responses were generally significantly smaller than corresponding harmonics obtained from sub-threshold responses. By contrast the amplitude differences between populations of threshold and sub-threshold responses were generally non-significant. These findings suggested that fully objective methods of threshold determination might more successfully be based on ensemble phase measures rather than amplitude measures.

Animals↗
PubMed1993

Efficiency of speech audiometry and other tests.

A formula for expressing the efficiency of audiological tests is proposed: E = (vb/vw - 1)/T where vb is the variance between subjects, vw is the variance within subjects and T is the testing time. This makes it possible to compare various tests even if they require different testing times. The formula has been used on various speech tests and on pure-tone thresholds for a specific group of hearing-impaired subjects, showing that pure-tone threshold tests are much more efficient than speech tests. Some suggestions are given on how to make speech tests in noise more efficient. It is concluded that the proposed formula of test efficiency should be considered when new tests are designed in order to get quick tests which add as much information as possible.

Analysis of Variance↗