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A method was developed to deliver tonebursts ranging in frequency from 1 to 32 kHz for frequency-specific assessment of the canine cochlea. Brainstem auditory-evoked responses (early latency responses, 0-10 ms) to a click (CS) and to 1-, 2-, 4-, 8-, 12-, 16-, 24-, and 32-kHz toneburst stimulations (TS) were compared at 80-dB sound pressure level stimulus (SPL) intensity in 10 adult dogs. All stimulations yielded a 5-7 positive wave pattern, with the exception of the 1-kHz TS, which evoked a frequency-following response (FFR). Thresholds were lowest for the CS and the 12- and 16-kHz TS. All individual peak latencies for TS were significantly (P < or = .05) longer than for CS. Peak I latencies were significantly (P < or = .05) shorter for the 12- and 16-kHz TS than for the other TS. Interpeak latencies I-V were significantly (P < or = .05) longer for the 4- to 32-kHz TS than for CS. Differences in interpeak latencies I-III were not significant. Amplitudes of waves I and V were significantly (P < or = .05) lower for TS than for CS, except for higher wave V amplitude (P < or = .05) at 2- and 32-kHz TS. Peak I-V amplitude ratios were significantly (P < or = .05) higher for the 2-, 4-, 16-, 24-, and 32-kHz TS and lower for the 8- and 12-kHz TS, compared to CS. We conclude that reproducible information on frequency specificity of the canine cochlea can be obtained by TS. This report provides a normative database for parameters needed to evaluate frequency-specific hearing loss in dogs.

This study examines the usefulness of the upward chirp stimulus developed by Dau et al. [J. Acoust. Soc. Am. 107, 1530-1540 (2000)] for retrieving frequency-specific information. The chirp was designed to produce simultaneous displacement maxima along the cochlear partition by compensating for frequency-dependent traveling-time differences. In the first experiment, auditory brainstem responses (ABR) elicited by the click and the broadband chirp were obtained in the presence of high-pass masking noise, with cutoff frequencies of 0.5, 1, 2, 4, and 8 kHz. Results revealed a larger wave-V amplitude for chirp than for click stimulation in all masking conditions. Wave-V amplitude for the chirp increased continuously with increasing high-pass cutoff frequency while it remains nearly constant for the click for cutoff frequencies greater than 1 kHz. The same two stimuli were tested in the presence of a notched-noise masker with one-octave wide spectral notches corresponding to the cutoff frequencies used in the first experiment. The recordings were compared with derived responses, calculated offline, from the high-pass masking conditions. No significant difference in response amplitude between click and chirp stimulation was found for the notched-noise responses as well as for the derived responses. In the second experiment, responses were obtained using narrow-band stimuli. A low-frequency chirp and a 250-Hz tone pulse with comparable duration and magnitude spectrum were used as stimuli. The narrow-band chirp elicited a larger response amplitude than the tone pulse at low and medium stimulation levels. Overall, the results of the present study further demonstrate the importance of considering peripheral processing for the formation of ABR. The chirp might be of particular interest for assessing low-frequency information.

In order to test the frequency specificity of the efferent suppressive effect on otoacoustic emissions, changes in the 2f1-f2 distortion product otoacoustic emission (DPOAE) levels induced by contralateral stimuli of different spectra were measured in 10 normally hearing adults. Three types of contralateral stimuli were used: (i) a set of 6 pairs of pure tones with the same frequencies as used for DPOAE stimulation; (ii) 6 narrow-band noise signals with cut-off frequencies equal to the frequencies of the primary tones used for DPOAE stimulation; and (iii) broad-band noise with a bandwidth of 840-6,000 Hz. A small suppressive effect was observed mainly in the mid-frequency region. Broad-band noise was more effective at suppressing DPOAEs than narrow-band noises and two-tone complexes. Occasionally, small enhancements in DPOAE amplitudes were observed. Based on the results of this study, it is concluded that DPOAE changes induced by contralateral stimuli are not frequency-specific, and are too small to have routine clinical value.

For intraoperative monitoring of auditory nerve function, the auditory steady-state response (ASSR) analysis may be an alternative to brain stem auditory evoked potentials, offering frequency specificity and short detection times. Clinical studies investigating the viability of ASSR under total intravenous anesthesia have not been performed.During craniotomy under total intravenous anesthesia with propofol and remifentanil in 20 patients, ASSR were recorded. An additional control patient undergoing cerebellopontine angle surgery was included, in whom the auditory nerve could not be preserved. One-minute sinus tones (500, 1,000, 2,000 Hz) were applied with 60-, 70-, and 80-decibel hearing level. Stimuli were amplitude modulated with 40, 90, or 110 Hz and applied monaurally to the left and right ears. Time to detect a significant response and response amplitudes at 40, 90, or 110 Hz in the evoked EEG spectra was evaluated.Overall, 90-Hz ASSR were successfully detected in all 20 patients, 110 Hz in 18 patients, and 40 Hz in 14 patients after a median of 10 seconds. No ASSR could be detected in the control patient at the end of the surgical procedure. Time-to-significance and ASSR amplitudes were influenced by stimulus intensity, carrier, and modulation frequency (Scheirer-Ray-Hare test, P0.005). Ipsilateral responses were higher than contralateral (P0.0001).In conclusion, 90- and 110-Hz ASSR can be reliably detected under total intravenous anesthesia. Our results are in line with those from previous studies in awake patients. Auditory steady-state response during anesthesia may enable intraoperative frequency-specific audiometry and monitoring of the auditory nerve.

On a variety of visual tasks, improvement in perceptual discrimination with practice (perceptual learning) has been found to be specific to features of the training stimulus, including retinal location. This specificity has been interpreted as evidence that the learning reflects changes in neuronal tuning at relatively early processing stages. The aim of the present study was to examine the frequency specificity of human auditory perceptual learning in a frequency discrimination task. Difference limens for frequency (DLFs) were determined at 5 and 8 kHz, using a three-alternative forced choice method, for two groups of eight subjects before and after extensive training at one or the other frequency. Both groups showed substantial improvement at the training frequency, and much of this improvement generalized to the nontrained frequency. However, a small but statistically significant component of the improvement was specific to the training frequency. Whether this specificity reflects changes in neural frequency tuning or attentional changes remains unclear.

Whether click-evoked otoacoustic emissions (CEOAEs) have frequency specificity is an issue still subject to debate. In order to resolve this issue, changes in the frequency components of the CEOAE power spectrum, together with changes in compound action potential (CAP) thresholds before and after pure-tone exposure in guinea pigs, were examined. Changes in CAP thresholds immediately before and 1 h after exposure were compared with changes in the frequency components in the CEOAE power spectrum before and 1 h after exposure. The ILO 88 was used for measurement of CEOAEs. Total echo energy in the CEOAE power spectrum was converted into frequency bands of 1000 Hz. Shifts in filtered echo power (FEP) levels correlated maximally with those in CAP thresholds at 0.5 kHz above the same frequency. Stepwise regression indicated that only one step could be entered in a linear regression model using the variable of CAP threshold shifts at 0.5 kHz above the same frequency for all FEP shifts except FEP4.5. The remaining variables played a negligible role, since variance no longer changed when they were included in the regression equation. From these results, it was concluded that CEOAEs display frequency specificity. Influence on CEOAEs from higher frequencies is negligible.

The relations of the stiffness and damping performance to the structure parameters of an active magnetic bearing (AMB) system and the frequency specificity of the control loop are analyzed. The effects of the control current phase on the stability, the stiffness and the damping properties of the system are presented. Meanwhile, a new concept of complex damping coefficient, the practical meanings of some system properties, and the calculation methods are discussed and described.

The effects of stimulus rise-fall and plateau times on the middle-latency response (MLR) waveform (Na-Pa amplitude and Pa latency) were investigated in 14 normally hearing subjects and an objective MLR threshold was evaluated at low and middle frequencies in ten normally hearing subjects and ten patients with slope of sensorineural hearing loss, using a selected stimulus-envelope time. After analyzing the effects of envelope times on the MLR waveform and the spectra of tone-pips, it was found that a rise-fall time of 4 ms with a plateau of 2 ms (4–2–4) is an acceptable compromise between a synchronous discharge and frequency specificity for estimating the MLR threshold. The MLR threshold produced by 4–2–4 tone-pips approximated the psychoacoustic threshold at low and middle frequencies in the normal and hearing impaired subjects. This demonstrates the clinical usefulness of the MLR in estimating low- and middle-frequency thresholds.

In this study, a preparation was developed which continuously monitored the f2−f1, 2 f1−f2, and 3f1−2 f2 distortion products in guinea pigs, in response to various contralateral and ipsilateral tones and broadband noise. A consistent decline over time in the quadratic distortion product, f2−f1, with continuous ipsilateral stimulation was observed, confirming previous findings by Kirk and Johnstone [Hearing Res. 67, 20–34 (1993)]. Broadband noise applied to the contralateral ear simultaneously increased both the magnitude and the rate of decline. This effect was shown for primaries across all frequencies tested (f2 from 2–16 kHz, f2/f1 ratio of 1.26), though a maximal effect was found for f2 of 4 kHz. Experiments using contralateral tones demonstrated a half-octave shift in the frequency specificity of this effect. A more “immediate” suppression effect on 2 f1−f2 (0.6 dB) was found in animals awakening from anesthesia, though this was even larger for f2−f1 (5.1 dB). Extended ipsilateral stimulation with co...

Both distortion product emissions and transiently evoked emissions typically exhibit an individual fine structure, which seems to be linked to the fine structure of threshold in quiet observable in many normal hearing subjects. However, the recording paradigm for both experiments is rather different. Narrow‐band distortion product emissions are detectable during continuous stimulation with two sinusoids. They represent the nonlinear interaction of the two tones in a stationary condition. Transient evoked emissions on the other hand may be interpreted as a type of impulse response of a nonlinear system. The frequency specificity is comparatively low. The interrelation of both types of emissions is not completely understood until now. To test the hypothesis of a common origin, patterns of spectral fine structure of DPOAE and TEOAE results from normal hearing subjects are compared. In addition, the influence of suppressor tones is investigated in both experiments. Results will be discussed in connection to c...

Auditory brainstem response (ABR) is a useful method in evaluating auditory function in human. To investigate the ABR threshold is more effective than to pursue the trends in each component of ABR. In this study, tone burst sound stimuli were employed and the ABR threshold shift caused by kanamycin administration was investigated in dogs. In a series of monitoring of ABR against short-period auditory lesions, changes in the ABR waveform after intravenous administration of kanamycin were detected. These changes returned gradually and were reversible. The changes in ABR against long-period auditory function disorder were perceived by an increase in the ABR threshold. The ABR threshold shift occurred earlier in the high frequency sounds than in the lower frequency sounds. This is why amino glycoside antibiotics damage the cochlear hair cells in the basal layer and lead to the loss of hearing selectively for high frequency tones. These findings suggest that tracing of the ABR threshold by tone bursts could provide information that has a specificity for frequency in hearing tests and is a useful method in clinical veterinary medicine or/and toxicological tests.

Transiently evoked otoacoustic emission (TEOAE), distortion product otoacoustic emission (DPOAE), and spontaneous otoacoustic emission (SOAE) were measured in 45 full-term neonates (68 ears) and 12 preterm neonates (20 ears) with ILO88 & 92. Measurements were performed in the nursery of the obstetrics ward or NICU (not sound proof room) under natural sleeping condition after nursing. No sedating agent was used. TEOAEs were rated “good response” in 61 (89.7%) of 68 full-term neonate ears. DPOAEs were rated “good response” in 40 (71.4%) of 56 full-term neonate ears. SOAEs were detectable in 25 (62.5%) of 40 full-term neonate ears. Considering the high positive rate of TEOAE in full-term neonates and the easy and noninvasive method of measurement, we concluded that TEOAE is useful for auditory screening in neonates. There was failure to detect TEOAEs in 7 ears and the measurements were all performed within 6 days after birth. Some reports claim that residual amnion in the external auditory canal or the middle ear in the first few days after birth causes slight hearing loss. Thus, we expected that making the measurements more than 7 days after birth might yield higher “good response” rates. We sometimes found that the Total Echo Powers of TEOAEs were reduced by the poor condition of the ear probe. Thus, we must be very careful in regard to this technical problem in order to perform accurate examinations. Because of its lower “good response” rate, DPOAE was not as useful for screening as TEOAE. Because of the movements or respiratory noises of the newborn infants, it was hard to detect reliable DPOAEs, particularly in the low frequency range. On the other hand, because of its frequency specificity, particurally at high frequencies, DPOAE will be useful for detecting the partial hearing impairment such as congenital high-tone hearing impairment. It would be difficult to use SOAE as a clinical test. Because it is not an evoked response, its mechanism of generation is not well understood. We expect that following longitudinal changes in SOAE in neonates may yield some information about it.We measured mainly TEOAE in preterm neonates because we had to complete the measurements as soon as possible. High Total Echo Powers of TEOAEs were recorded in most infants over 38 weeks of PCA (post-conceptional age). The earliest case showed reliable TEOAE at 35 weeks PCA. In most cases that could be measured twice on different days, the Total Echo Powers of TEOAE, were higher in the second time. We therefore concluded that TEOAE might serve as an examination for monitoring the maturation of preterm neonate hearing.

Transient-evoked otoacoustic emissions (TEOE) disappear when hearing loss exceeds 40 dB in the range 1-4 kHz, due to impairment of cochlear outer hair cells. Early screening of sensorineural hearing losses is based on this finding. However, little is known as to the frequency specificity of TEOE abnormalities in a damaged cochlea. TEOE were recorded in 18 normally hearing guinea pigs in a range from 1.5 to 5 kHz before and after exposure to loud pure tones (3-10 kHz, 95-105 dB SPL, 1-10 min). The thresholds of eighth-nerve compound action potentials (CAP) were monitored with a round-window electrode; it was confirmed that acoustic overexposure resulted in typical high-frequency threshold elevations (10 to 50 dB). Most TEOE components were found at lower frequencies at which CAP thresholds did not change. However, a significant linear regression was found between their amplitudes and the percentage of basal cochlea with unaltered CAP thresholds (r = 0.69, p0.0001). Two alternative hypotheses are proposed to account for this correlation. Either acoustic trauma induced some minute cochlear damage at places tuned to low frequencies and TEOE were more sensitive to it than CAP thresholds, or significant contributions to lower-frequency TEOE came from the most damaged cochlear places tuned to much higher frequencies.

Transiently evoked otoacoustic emissions (TEOAE) are present in nearly all normal hearing ears and recognized as useful for objective auditory screening. In the spectral analysis of TEOAE with click stimuli, the normal power spectrum of TEOAE has yet to be obtained. In this study, the normal range of the power spectrum was determined for 42 adults with normal hearing and compared with sensorineural hearing disturbance data. The power spectrum of TEOAE in normal hearing adults sloped down at high frequencies and was the same for right and left ears in both males and females. For comparison with sensorineural hearing disturbance, a significant correlation between the audiogram and power spectrum of TEOAE was sought. Frequency specificity was noted in the power spectrum of TEOAE with click stimulation.

The influence of contralateral auditory stimulation on otoacoustic emissions (OAE), spontaneous OAE, evoked OAE and acoustic distortion products, can be summarized as follows: (1) alteration (mainly a decrease) of OAE amplitude; (2) alteration of response spectrum (upward shift frequency of SOAE); (3) alteration of phase; (4) effect dependent on intensity of contralateral stimulation; (5) effect inversely dependent on intensity of ipsilateral stimulation; (6) frequency specificity of the suppressive effect. Involvement of the medial olivocochlear bundle is highly probable but one cannot exclude a double pathway including also the acoustic reflex.

The frequency characteristics of the suppression by contralateral stimulations, of the cubic 2 f 1 − f 2 distortion products (DPOAEs), were studied during 63 sessions performed in 39 humans with normal hearing. Each session consisted of exposure to five successive series of randomized contralateral NBN frequencies centered between 0.25 and 8 kHz, while measuring 2 f 1 − f 2 set at one of the four studied frequencies, i.e., 1, 2, 3 or 5 kHz. For each value of 2 f 1 − f 2 , analysis of variance and Student's t -test were used in order to indicate and, if necessary, to localize, a possible significant frequency specificity. Results showed that the suppression exerted on 2 f 1 − f 2 DPOAEs by contralateral sound stimulation, is frequency specific, at least for middle frequencies of 1 and 2 kHz. The frequency specificity is specially marked when 2 f 1 − f 2 = 1 kHz with contralateral NBN central frequencies around 1 kHz. When 2 f 1 − f 2 = 2 kHz, central frequencies which induced a significant suppressive effect include frequencies around 2 kHz and also lower frequencies around 1 kHz. These observations support the interpretation that the suppression of the DPOAE is mediated by the medial olivo-cochlear efferent system.

The influence of noise bandwidth on the contralateral masking of click-evoked otoacoustic emissions was investigated by recording emissions from 20 normal subjects with contralateral narrow-band noise, with wide-band noise and without contralateral noise for comparison. Narrow-band noise of five different centre frequencies and three different bandwidths per frequency was used at intensities of 40 and 60 dB SL. Analysis of the emissions showed that the 40-dB SL contralateral noise did not produce a significant amount of suppression. The suppression produced by 60-dB SL noise was spread throughout the frequency range of the emissions, with limited frequency specificity. There was some evidence that the amount of suppression increases with the bandwidth of the noise, particularly for noises centred on 1 and 2 kHz; the wide-band noise produced much greater suppression than any of the narrow bands. There was a large amount of inter-subject variation, which could not be explained by differences in the absolute level of the emissions. One subject with a total unilateral hearing loss in the contralateral ear was also tested, and gave no significant suppression.

The apparent motion of a fixated spot stimulus during head oscillations (apparent concomitant motion, ACM) was measured before and after an adaptation period during which the fixation stimulus moved in synchrony with the head. During the adaptation period, the fixation stimulus moved either in the same (with) or the opposite (against) direction as did head movement. With adaptation increased ACM in the direction opposite head motion, whereas against adaptation increased ACM in the same direction as head motion. Pre- and postadaptation measures were obtained for .25-, .5-, 1.0-, and 2.0-Hz active head movements. Each of these frequencies was used in separate sessions as the adaptation frequency. ACM changes were greatest when the test and adaptation frequencies were the same, demonstrating frequency specificity of ACM adaptation. This frequency specificity, which is similar to that of the vestibulo-ocular reflex, indicates that ACM adaptation may reflect plasticity in oculomotor systems.

To investigate the frequency specificity of steady-state responses elicited with a sinusoidally amplitude-modulated tone (amplitude-modulation-following response, AMFR), AMFR at different carrier frequencies were examined in 15 subjects with normal hearing, 12 patients with abrupt high-frequency hearing loss, 5 patients with low-frequency hearing loss and 1 patient with mid-frequency hearing loss. The stimulus was a sinusoidally amplitude-modulated tone with a modulation frequency of 40 Hz and modulation depth of 95%. Carrier frequencies were from 250 to 4000 Hz in normal subjects and from 250 to 8,000 Hz in hearing-impaired subjects. Fridman's phase spectral analysis was conducted for automatic detection of response. The thresholds of AMFR were distributed within 30 dB nHL at all carrier frequencies in normal subjects. In the hearing-impaired subjects, AMFR thresholds were between 0 and 25 dB above the behavioral threshold at all carrier frequencies. The threshold patterns of AMFR detected by phase spectral analysis very closely resembled the corresponding audiogram patterns in all types of hearing impairment. AMFR is thus shown to have a very good frequency specificity.

Dr. Einar Laukli, IJA Associate Editor EmeritusIn short latency electrophysiology such as auditory brainstem response (ABR) and 80-Hz auditory steady-state response (ASSR) testing, as well as in el...

The onset and frequency-following response (FFR) components of the auditory brain stem response were investigated using a tone on tone forward-masking paradigm, as an alternate strategy to simultaneous masking, in an effort to further clarify the issue of place specificity of these components when elicited by a low-frequency stimulus (500 Hz tone burst). The results of this preliminary investigation suggest that both the onset and FFR components yield frequency-specific information, that is, they reflect activity along a limited apicalward region of the cochlea, but both are biased somewhat basalward to the place of the probe frequency. Also, of the two, the FFR is the relatively more place-specific response.

Several investigators have suggested that the use of tonal stimuli shaped with nonlinear windowing functions can improve the frequency specificity of the auditory brain stem response (ABR). This study investigated the effects of different windowing functions on the ABR for 30 normal-hearing adults and 30 adults with high-frequency hearing loss. These hearing-impaired patients often produce an abnormal click-evoked ABR because of the influence of the high-frequency loss. Each subject was evaluated using a click stimulus and a 500 Hz tone burst gated with one linear and four nonlinear windowing functions. There were no significant differences in wave V latency between the groups for any of the five windowed tone burst conditions. These results suggest that any of the windowing functions used would be effective for 500 Hz tonal ABRs with this population of hearing-impaired adults.

Clinical applications of otoacoustic emissions (OAEs) have long been studied since the discovery of this surprising phenomenon by D. T. Kemp in 1978. Although there are at least 4 classes of OAEs, i. e., transiently evoked OAE (EOAE), spontaneous OAE, synchronously evoked OAE and distortion product OAE (DPOAE), most researchers have attempted to evaluate EOAE as a possible measure of cochlear pathology. However, the results only indicate that the EOAE does not provide much information about the fine distribution of cochlear lesions. On the other hand, the measurement of the DPOAE has recently become available as another possible indicator of cochlear function, and has great advantages over EOAE measurement. The results of DPOAE measurement in sensorineural hearing-impaired patients clearly indicate that the DPOAE has excellent frequency specificity. In most cases, the DP-audiogram, a plot of DPOAE level against stimulus frequency, exactly reflects the longitudinally distributed integrity of the cochlear partition. This method may become the most powerful non-invasive tool for the evaluation of cochlear function.

A frequency-specific, objective assessment of hearing thresholds is required for use in subjects unable to perform behavioural audiometry. One such method using steady-state evoked potentials (SSEPs) in response to amplitude-modulated tones was evaluated in an experimental animal, the macaque monkey. An amplitude-modulation frequency of 165 Hz was found to produce optimum response detection in the anaesthetised animal. Auditory thresholds determined by a computerised automatic response detection system accurately reflected behavioural thresholds previously described in this species.

This study examined the neural basis of auditory selective attention using functional magnetic resonance imaging. The main hypothesis stated that attending to a particular sound frequency would significantly enhance the neural response within those tonotopic regions of the auditory cortex sensitive to that frequency. To test this prediction, low- and high-frequency sound sequences were interleaved to produce two concurrent auditory streams. Six normally hearing participants either performed a task which required them to attend to one or the other stream or listened passively to the sounds while functional images were acquired using a high-resolution (1.5 mm × 1.5 mm × 2.5 mm) sequence. Two statistical comparisons identified the attention-specific and general effects of enhancement. The first controlled for task-related processes, while the second did not. Results demonstrated frequency-specific, attention-specific enhancement in the response to the attended frequency, but no response suppression for the unattended frequency. Instead, a general effect of suppression was found in several posterior sites, possibly related to resting-state processes. Furthermore, there was widespread general enhancement across auditory cortex when performing the task compared to passive listening. This enhancement did include frequency-sensitive regions, but was not restricted to them. In conclusion, our results show partial support for frequency-specific enhancement. © 2009 Elsevier B.V. All rights reserved.

Click ABR wave V thresholds in the first year were compared with follow-up behavioural pure-tone audiometry under earphones at age 3 to 6 years in 713 infants (yielding 1,367 ears) at risk for hearing loss. The observed accuracy of the ABR depends strongly on the precise definitions of the target disorder and the test abnormality criteria. For sensorineural hearing loss of more than 20 dB averaged at 2 kHz and 4 kHz, the click ABR provides an accurate test, with both false positive and false negative rates of less than 10%, using an ABR threshold criterion of 30 dB nHL. The false positive error rate can be at least halved by using a simple rule for wave V latency that discriminates conductive and sensorineural ABR threshold abnormalities. False negative errors may be explicable in terms of the lack of frequency specificity of the click stimulus.

The prevalence of red blood cell (RBC) alloantibodies among general, hospital-based patients typically has averaged approximately 1 percent in various studies. The frequency and properties of RBC alloantibodies in military veterans has never been examined.Transfusion records of 18,750 military veterans at a Department of Veterans Affairs (VA) medical center were retrospectively reviewed. For patients with RBC alloantibodies, the following were collected: sex, race/ethnicity, decade of birth, transfusion history, alloantibody specificity, reaction phase(s), and whether alloantibodies were detected at the initial type and screen or later.The RBC alloantibody prevalence was 2.4 percent among predominantly male military veterans. Alloantibody prevalence varied with decade of birth, ranging up to 3.3 percent (1911-1920). The 10 most frequent alloantibodies in males, as a percentage of total male antibodies, were K (21.9%), E (19.4%), D (9.1%), Le(a) (7.4%), Fy(a) (5.4%), c (4.8%), C (4.6%), P(1) (3.9%), Jk(a) (3.7%), and Le(b) (3.5%). Investigation of D alloimmunization in men revealed that antibody development occurred before VA care in 80 percent (39/49) of cases. For alloimmunization during VA care, anti-D was mostly associated with the transfusion of D+ platelets (7/10). The majority of alloantibodies in males reacted at the antiglobulin (AG) phase, even anti-Le(a), -Le(b), M, -Lu(a), and -P(1).Military veterans have a relatively high prevalence of RBC alloantibodies, including anti-D, despite a large male predominance and lack of pregnancy-related alloimmunization. Alloantibody prevalence was highest in World War II veterans. The majority of male alloantibodies reacted with AG, even those traditionally considered to be clinically insignificant.

Background. Tone-burst otoacoustic emissions (TBOAEs) have not been routinely studied in pediatric populations, although tone burst stimuli have greater frequency specificity compared with click sound stimuli. The present study aimed (1) to determine an appropriate stimulus level for neonatal TBOAE measurements when the stimulus center frequency was 1 kHz, (2) to explore the characteristics of 1 kHz TBOAEs in a neonatal population. Methods. A total of 395 normal neonates (745 ears) were recruited. The study consisted of two parts, reflecting the two study aims. Part I included 40 normal neonatal ears, and TBOAE measurement was performed at five stimulus levels in the range 60-80 dB peSPL, with 5 dB incremental steps. Part II investigated the characteristics of the 1 kHz TBOAE response in a large group of 705 neonatal ears, and provided clinical reference criteria based on these characteristics. Results. The study provided a series of reference parameters for 1 kHz TBOAE measurement in neonates. Based on the results, a suggested stimulus level and reference criteria for 1 kHz TBOAE measures with neonates were established. In addition, time-frequency analysis of the data gave new insight into the energy distribution of the neonatal TBOAE response. Conclusion. TBOAE measures may be a useful method for investigating cochlear function at specific frequency ranges in neonates. However, further studies of both TBOAE time-frequency analysis and measurements in newborns are needed. © 2008 Zhang et al; licensee BioMed Central Ltd., published_or_final_version

In normal-hearing subjects and in subjects with a flat cochlear hearing loss, auditory brainstem responses (ABR) were recorded at various levels of a 1,000-Hz filtered click stimulus with and without high-pass filtered masking noise. The difference in latency of the major peak in the ABR for the masked and unmasked condition was zero at the ABR threshold. We regard this as proof of the frequency specificity of the 1,000-Hz filtered click-stimulated ABR threshold. The difference between ABR threshold and the subjective puretone threshold at 1,000 Hz amounted to 19 dB in normal-hearing subjects and to 10 dB in subjects with a flat cochlear hearing loss. This is probably related to loss of temporal integration and an abnormal loudness growth (recruitment).

Automatic threshold detection techniques are described for auditory steady-state response (ASSR) elicited with a sinusoidally amplitude-modulated tone. The reliability and frequency specificity of ASSR are discussed. When applied to awake adults and detected by phase spectral analysis, 40-Hz ASSR threshold patterns closely resemble their corresponding audiograms. However, 40-Hz ASSR is insufficiently reliable for determining hearing thresholds in young children during sleep. On the other hand, 80-Hz ASSR is detected clearly in sleeping children. Moreover, 80-Hz ASSR threshold patterns also closely resemble the corresponding audiograms. Therefore, 80-Hz ASSR appears to be useful for objective audiometry in children.

When trying to detect a tonal signal in a continuous broadband noise, listeners attend selectively to both the frequency and the duration of the expected signal. However, it is not known whether they monitor separate or combined representations of these two attributes. To investigate this question, a probe-signal method was used to measure the detectability of signals of expected and unexpected durations at two expected frequencies. The four listeners expected only one of two signals to be presented at random: a brief tone at one frequency or a long tone at another frequency. For each signal frequency, the detectability of the signals of unexpected duration decreased to near chance as the difference between the expected and unexpected duration, at that frequency, increased. The frequency specificity of this duration tuning indicates that both the frequency and the duration of an expected stimulus are represented in a single template.

Distortion product otoacoustic emissions (DPOAEs) are thought to stem from the outer hair cells (OHCs) around the normally narrow place tuned to the primary tone stimuli. They are thus said to be frequency-specific: their local absence should accurately pinpoint local OHC damage. Yet the influence of impaired tuning on DPOAE frequency specificity is poorly documented. Mice with local damage to OHCs were examined. Their DPOAEs were frequency-specific in that audiometric notches were accurately tracked. The same cochleae were further impaired by ischemia or furosemide injection inducing strial dysfunction with flat loss of sensitivity and tuning, while the preexisting pattern of damaged OHCs remained unaltered. Despite the loss of cochlear activity, DPOAEs produced by high-level (or =70 dB SPL) primaries remained large in about the same interval where they had been initially normal, i.e., that with nondamaged OHCs, albeit with a slight frequency shift, of -1.1 kHz on average. Thus, the ability of DPOAEs to map structurally intact OHCs cannot be a mere consequence of cochlear tuning as it largely persists in its absence. The key element for this correct mapping is likely part of intact OHC structures (e.g., stereocilia bundles) and must have some tuning of its own.

The effect of frequency on N1m has been investigated by various methods. However, it has not yet been measured using forward masking. In this study, the frequency specificity of N1m was investigated using forward masking. Although the masker frequency had some influence on N1m amplitudes, the results suggested that the frequency specificity of N1m was worse than that of a single-neuron or psychological tuning curve. This is probably because N1m includes various components, both frequency-specific and non-specific, some of which may be less affected by masking. Thus, our results agree with those of previous studies using intervening tones that suggested widespread neural representation in the auditory cortex.

Frequency specificity of pulsed electro-magnetic energy is one of the most important factors in obtaining maximum benefits for pain relief and healing of damaged tissue. Waveforms, the harmonics available and the ON-OFF duty cycle must also be considered, and these are discussed. In summary, the parameters of the specifics discussed, demonstrate the most effective results to date in clinical use of extremely ultra low frequency pulsed electromagnetic field energy, over other previously accepted methodology. Further research and data collection from clinical studies are on-going to identify additional beneficial biological effects in this cutting edge of modern medical technology.

This study investigated the frequency specificity of the auditory brainstem and middle latency responses to 80 and 90 dB ppe SPL 500-Hz and 90 dB ppe SPL 2000-Hz tonebursts. The stimuli were brief (2-1-2 cycle) linear-gated tonebursts. ABR/MLRs were recorded using two electrode montages: (1) Cz-nape of neck and (2) Cz-ipsilateral earlobe. Cochlear contributions to ABR wave V-Na and MLR waves Na-Pa and Pa-Nb were assessed by plotting notched noise tuning curves which showed amplitudes and latencies as a function of center frequency of the noise masker [Abdala and Folsom, J. Acoust. Soc. Am. 97, 2394 (1995); ibid. 98, 921 (1995)]. Maxima in the response amplitude profiles for the ABR and MLR to 80 dB ppe SPL tonebursts occurred within one-half octave of the nominal stimulus frequency, with minimal contributions to the responses from frequencies greater than one octave away. At 90 dB ppe SPL, contributions came from a slightly broader frequency region for both stimulus frequencies. Thus, the ABR/MLR to 80 dB ppe SPL tonebursts shows good frequency specificity which decreases at 90 dB ppe SPL. No significant differences exist in frequency specificity of: (1) ABR wave V-Na versus MLR waves Na-Pa and Pa- Nb at either stimulus frequency or intensity; and (2) ABR/MLRs recorded using the two electrode montages.

Two experiments examined the frequency specificity of habituation of the acoustic startle response in the rat. Following the long-term habituation of startle to one of two pure tone stimuli in Experiment 1, animals were presented with the other stimulus. Startle response asymptotes were unaffected by this change in stimulus frequency. Short-term habituation of startle also was insensitive to stimulus frequency. In Experiment 2, pure tone stimuli were used to provoke both a startle response and the interruption of drinking. Long-term habituation of startle to either stimulus was unaffected by a change in frequency. Animals that received the two stimuli on alternating days showed as rapid a habituation as did the groups receiving only one stimulus frequency during acquisition. Conversely, the lick suppression measure was found to be frequency specific. Lick suppression durations rose to pre-habituation levels when the frequency of the stimulus was changed. Animals that received the two stimuli on alternating days showed retarded habituation compared to those groups presented with only one stimulus frequency during acquisition. Although long-term habituation of startle is not stimulus specific, it is mediated by central processes and thus remains a valuable model in the study of neurophysiological mechanisms of behavioral change.

This study investigated the frequency specificity of the auditory brainstem (ABR) and middle latency (MLR) responses to 500- and 2000-Hz brief tones using high-pass noise masking. Stimuli were linear- (2-1-2 cycles) and exact-Blackman- (5 cycles) gated tones presented at 80 dB peak-to-peak equivalent (ppe) SPL. Cochlear contributions to ABR wave V-V' and MLR wave Na-Pa were assessed by the effects of high-pass noise masking on response amplitudes and latencies. The high-pass noise results demonstrate that the ABR and the MLR to the 80 dB ppe SPL brief tones show good frequency and place specificity. Changes in ABR or MLR amplitude and latency with high-pass noise masking did not occur as the masker cutoff was decreased from 2 to 3 octaves above the stimulus nominal frequency until it was within one-half octave of this frequency, below which amplitudes rapidly decreased (500- and 2000-Hz tones) and latencies increased (500-Hz tones). No significant differences existed in the frequency specificity of the ABR versus MLR, or in these evoked potentials to exact-Blackman- versus linear-gated tones.

This study investigated the frequency specificity of the auditory brainstem (ABR) and middle latency (MLR) responses to 500- and 2000-Hz brief tones using narrow-band derived response analyses of the responses recorded in high-pass masking noise [Oates and Stapells, J. Acoust. Soc. Am. 102, 3597-3608 (1997)]. Stimuli were linear- and exact-Blackman-gated tones presented at 80 dB ppe SPI. Cochlear contributions to ABR wave V-V' and MLR wave Na-Pa were assessed by response amplitude profiles as a function of derived band center frequency. The largest amplitudes of waves V and Na-Pa occurred in the 500- and 707-Hz derived bands in response to the exact-Blackman- and linear-gated 500-Hz tones. The peak in the response amplitude profiles for wave V to both 2000-Hz stimuli was seen in the 2000-Hz derived band. For wave Na-Pa, the maxima in the amplitude profiles occurred in the 2000- and 1410-Hz derived bands for the exact-Blackman- and linear-gated tones. Smaller cochlear contributions to the ABR/MLR were also present at 0.5-1 octave above and below the nominal stimulus frequencies. The ABR/MLR to 500- and 2000-Hz 80 dB ppe SPL tones thus shows good frequency specificity, with no significant differences in the frequency specificity of: (1) ABR versus MLR; (2) these evoked potentials to 500-versus 2000-Hz tones; and (3) responses to exact-Blackman- versus linear-gated tones.

Transiently evoked otoacoustic emissions (TEOAE) and distortion product otoacoustic emissions (DPOAE) can be quantified concerning their amplitude and frequency. They are known to be diminished or absent in sensorineural hearing loss. It is therefore of interest how TEOAE and DPOAE correlate with the auditory threshold and whether the auditory threshold can be predicted by these variables. In a cross sectional study of 61 patients (102 ears) with sensorineural hearing loss, auditory threshold, tympanometry, stapedius reflexes, TEOAE and DPOAE were measured. Correlation coefficients of the hearing loss (0.5-6 kHz) and the amplitude of the distortion product 2f1-f2 (0.46 4 kHz) respectively TEOAE amplitude (1-4 kHz) were computed. TEOAE showed lower correlation coefficients and less frequency specificity than DPOAE. In order to increase the correlations with the auditory threshold we fitted a multivariate linear regression model with TEOAE and DPOAE simultaneously as predictors for the auditory threshold gaining 95% prediction intervals of 19-39 dB depending on the frequency investigated. By restricting the hearing loss to a maximum of 70 dB HL the 95% prediction interval of the auditory threshold could be decreased to 18-26 dB. Further improvements can be expected if the high inter- and intraindividual variability of TEOAE and particularly DPOAE measurements can be reduced. The results allow us to use TEOAE and DPOAE in addition to click-evoked brainstem audiometry in order to provide more frequency specific information about the hearing loss in newborns, which is of the utmost importance for an ideal fitting of hearing aids.

This study investigated the effects of signal-to-noise ratio (S/N) on the latency and amplitude of the auditory brainstem response (Wave V) using 1 and 4 kHz tone bursts in notch noise and broadband noise. Normal listeners were presented with 40 dB and 80 dB nHL tone bursts in quiet and in noise at S/Ns of 10, 15, 20, and 25 dB. The latency data suggest that at low intensity levels tone bursts in quiet may be preferred to testing in noise. At moderate and high intensities, however, notch noise or broadband noise is preferred to the quiet condition because of the improved frequency specificity provided by the masking. When testing patients with flat or gradually sloping audiometric configurations at moderate to high intensities with 4 kHz, either notch noise or broadband noise with an S/N of 15 to 25 dB may be used. When presenting 1 kHz tone bursts at high intensities to patients having flat and gradually sloping losses, a notch noise at S/Ns of 10 to 25 dB is preferred to broadband noise. The use of a notch noise at 10 dB S/N may be the stimulus of choice when testing patients with moderately to steeply sloping audiometric configurations with 1 or 4 kHz tone bursts.

The frequency specificity of the ABR threshold evoked by a 1000-Hz filtered click was determined in subjects with sloping cochlear hearing losses, both high- and low-frequency in character. The results show that the ABR threshold evoked by this stimulus is low-frequency specific. The standard error in estimating the 1000-Hz pure-tone threshold (PTT) is 10.4 dB, which equals that for estimating the 3 000-Hz PTT from the routinely used click-evoked ABR threshold [1]. The ABR threshold evoked by a 1000-Hz filtered click can therefore be regarded as an accurate tool to predict the pure-tone hearing loss at 1000-Hz. In comparison with the ABR threshold evoked by a click masked with 1590-Hz high-pass noise [6], the ABR threshold evoked by a 1000-Hz filtered click has a larger dynamic range, yields a larger number of useful responses and is less time consuming. For clinical low-frequency-specific ABR threshold assessment, the 1000-Hz filtered click is therefore preeminently useful.

Publisher Summary The measurement of transiently evoked otoacoustic emissions (TEOAEs) can identify a hearing loss exceeding 25–30 dB with high sensitivity. Distortion-product otoacoustic emission (DPOAE) measurements are being developed for clinical use and are more frequency-specific than TEOAEs. The TEOAEs and DPOAEs are compared in both normally hearing and hearing-impaired subjects to know more about the frequency specificity of these two types of emissions. In a first investigation, toneburst-evoked OAEs are compared to DPOAEs stimulated at 1, 2, and 4 kHz in ten ears without spontaneous otoacoustic emissions of ten normally hearing subjects. Input/output (I/O) functions of DPOAEs at frequency regions of 1 and 2 kHz are characterized by roll-overs and irregularities that are not present in either DPOAE I/O functions at 4 kHz or in TEOAE I/O functions at 1, 2. and 4 kHz. Mean slopes of the 110 functions increased with increasing frequency for DPOAEs and decreased for TEOAEs. In a second investigation, click-evoked OAEs and DPOAEs (stimulated by pure tones in the frequency range of 0.75–6 kHz) are measured in 42 ears of 21 normally hearing subjects and 128 ears of 64 subjects with varying degrees of sensorineural hearing loss.

Two experiments were performed in which 8 listeners used external sound to mask the tinnitus induced by a 95-dB SPL tone presented for 1 min. Wider bandwidth noises were more effective maskers than noises of critical bandwidth, which, in turn, were more effective than tonal maskers. Contralateral maskers were often effective, but less so than ipsilateral maskers. Tuning curves showed some degree of frequency specificity that was not related to the frequency of the tinnitus-inducing tone. There were consistent and pronounced differences between individual listeners. Overall, our results indicate both similarities and differences between the masking of induced tinnitus and the masking of pathological tinnitus.

In this study, the frequency specificity of the auditory brainstem response (ABR) threshold to a click masked with 1590-Hz high-pass masking noise is compared with the frequency specificity of the unmasked click-evoked ABR threshold. The ABR threshold to the high-pass-noise-masked click stimulus is low frequency specific and corresponds with the 1,000-Hz pure-tone threshold. Although the ABR threshold to the unmasked click stimulus corresponds with the '3,000'-Hz pure-tone threshold, the frequency specificity seems much less pronounced than that of the low-frequency-specific stimulus. This study shows, however, that this apparent lack of frequency specificity can be attributed to the selection of pure-tone hearing losses. The ABR threshold evoked by an unmasked click stimulus is, therefore, preeminently useful as a high-frequency point of a two-point audiogram. The possible reasons why the ABR threshold evoked by a broad-band stimulus as the unmasked click corresponds with the higher frequencies of the pure-tone audiogram are discussed.

The amplitude modulation-following response (AMFR) is an auditory scalp-recorded potential, evoked using continuous, amplitude-modulated tones. The current study was designed to explore the audiometric utility of the AMFR by demonstrating the frequency specificity of the response and assessing the relation between behaviorally measured pure-tone thresholds and AMFR detection thresholds. Subjects in this study were six normal-hearing and four hearing-impaired adults. High-pass masking results in the normal hearing subjects demonstrated that the AMFR is associated with a narrow range of activation along the cochlea around the carrier frequency. Frequency-specific results from the hearing-impaired subjects confirmed this finding. Thresholds for the AMFR, defined in spectral terms, were consistent with the behavioral estimates in both the normal and the hearing-impaired subjects.

Otoacoustic emissions provide an objective measure of hair-cell function that is independent of retrocochlear activity. Because of their frequency specificity, distortion-product emissions have great potential for clinical use. The present report describes the results of initial studies in patients with known cochlear or retrocochlear disease, diagnosed with standard otologic and audiologic tests. The cochlear group consisted of those diagnosed with noise-induced hearing loss, Meniere's disease, or hereditary hearing loss, whereas patients with acoustic neuroma comprised a retrocochlear group. A final group consisted of patients with sudden sensorineural hearing loss of unknown origin. Detailed distortion-product emission testing included the computer-controlled acquisition of "audiograms" and response/growth functions. The outcomes of these studies demonstrated that distortion-product emissions provide a noninvasive, frequency-specific test of sensory-cell function that objectively depicts the boundary between normal and abnormal hearing. These emissions were also able to effectively track dynamic changes in progressive disease processes. Finally, as a screening tool, acoustic distortion products provide an objective means of assessing cochlear status in infants and young children and in adults at risk for hearing loss. Because acoustic distortion products accurately measure the sensory component of a sensorineural hearing loss, distortion-product testing may play an important role in the diagnosis and treatment of cochlear dysfunction.

The reliability and frequency specificity of 80‐Hz auditory steady‐state response (80‐Hz ASSR) elicited by sinusoidally amplitude‐modulated (SAM tones) tones and detected by phase coherence were evaluated as a measure of the hearing level in young children. The 80‐Hz ASSR at a carrier frequency of 1000 Hz was monitored in 169 ears of 125 hearing‐impaired children and auditory brainstem response (ABR) elicited by tone pips was examined in 93 ears. Both responses were examined during sleep, and the thresholds were compared with the behavioral hearing threshold, which was determined by standard pure‐tone audiometry or play audiometry. In 24 ears with various patterns of audiogram, 80‐Hz ASSRs were examined at different carrier frequencies, and the threshold patterns were compared with the audiograms to investigate the frequency specificity of ASSR. The correlation coefficient between the threshold of 80‐Hz ASSR and pure‐tone threshold (r=0.863) was higher than that for ABR (r=0.828). The threshold patterns of 80‐Hz ASSR clearly followed the corresponding audiogram patterns in all types of hearing impairment. These findings suggest that 80‐Hz ASSR elicited by SAM tones and detected by phase coherence is a useful audiometric device for the determination of hearing level in a frequency‐specific manner in children.