High-pass Masking Research Articles

Relations between speech‐reception, psychophysical temporal processing, and subcortical electrophysiological measures of auditory function in humans

There is a large amount of variability in performance in masked-speech reception tasks, as well as in psychophysical auditory temporal processing tasks, between listeners with normal or relatively normal low-frequency hearing. In this study we used a cross-sectional dataset collected on 102 listeners (34 young, 34 middle-aged, 34 older) to assess whether variance in these tasks could be explained by variance in subcortical electrophysiological measures of auditory function (auditory brainstem responses and frequency following responses), and whether variance in speech-reception performance could be explained by variance in auditory temporal processing tasks. The potential confounding effect of high-frequency sensitivity was strictly controlled for by using highpass masking noise. Because each high-level construct (masked-speech reception, auditory temporal processing, and subcortical electrophysiological function) was indexed by several variables, we used principal component analyses to reduce the dimensionality of the dataset. Multiple-regression models were then used to assess the associations between the extracted principal components while controlling for a range of possible confounders including age and audiometric thresholds. We found that masked-speech reception was credibly associated with psychophysical auditory temporal processing abilities. No credible associations were found between masked-speech reception and electrophysiological measures of subcortical auditory function, or between psychophysical measures of auditory temporal processing and electrophysiological measures of subcortical auditory function. These results suggest that either the electrophysiological measures of subcortical auditory function used were not sufficiently sensitive to the subcortical neural processes limiting performance in the speech-reception and psychophysical auditory temporal-processing tasks, or that variance in these tasks is largely unrelated to variance in subcortical neural processes in listeners with near-normal hearing.

Effects of age on electrophysiological measures of cochlear synaptopathy in humans

Age-related cochlear synaptopathy (CS) has been shown to occur in rodents with minimal noise exposure, and has been hypothesized to play a crucial role in age-related hearing declines in humans. Because CS affects mainly low-spontaneous rate auditory nerve fibers, differential electrophysiological measures such as the ratio of the amplitude of wave I of the auditory brainstem response (ABR) at high to low click levels (WIH/WIL), and the difference between frequency following response (FFR) levels to shallow and deep amplitude modulated tones (FFRS-FFRD), have been proposed as CS markers. However, age-related audiometric threshold shifts, particularly prominent at high frequencies, may confound the interpretation of these measures in cross-sectional studies of age-related CS. To address this issue, we measured WIH/WIL and FFRS-FFRD using highpass masking (HP) noise to eliminate the contribution of high-frequency cochlear regions to the responses in a cross-sectional sample of 102 subjects (34 young, 34 middle-aged, 34 older). WIH/WIL in the presence of the HP noise did not decrease as a function of age. However, in the absence of HP noise, WIH/WIL showed credible age-related decreases even after partialing out the effects of audiometric threshold shifts. No credible age-related decreases of FFRS-FFRD were found. Overall, the results do not provide evidence of age-related CS in the low-frequency region where the responses were restricted by the HP noise, but are consistent with the presence of age-related CS in higher frequency regions.

Forward masking recovery in bottlenose dolphins (Tursiops truncatus): Auditory brainstem responses to paired-click stimuli in high-pass masking noise

Adaptation is a fundamental process in the auditory system and underlies the automatic gain control system of echolocating bottlenose dolphins. As pulse-echo delay increases, auditory brainstem response (ABR) amplitudes to the echoes progressively increase. This study examined adaptation across cochlear frequency regions using a paired-click (i.e., forward masking) paradigm and high-pass masking noise. Bottlenose dolphins passively listened to paired click stimuli (20–160 kHz “pink” spectra). A “conditioning” click was followed by a “probe” click with equal amplitude and a time delay ranging from 125 to 750 μs. ABRs to click pairs were obtained with and without high-pass masking noise that precluded the basal turn of the cochlea from responding to the click stimuli. The ABR evoked by a single click (temporally aligned with the first click of the paired-click condition) was subtracted from the click-pair ABR to visualize the response evoked by the probe click. Probe ABR amplitudes recovered linearly with increasing delay relative to the conditioning click, and were approximately 70% of full response amplitude at 750-μs delay. Paired-click interval ABR amplitude recovery functions were similar for the unmasked and high-pass masked conditions. [Work sponsored by ONR.]

Place specificity of dolphin auditory evoked potentials assessed with high-pass masking noise

Auditory evoked potential measurements are commonly used for hearing assessment in marine mammals for which psychophysical testing is not practical. Evoked potential measurements typically employ electrical signals consisting of short-duration tone-pips or sinusoidal amplitude modulated tones, which are then presented to piezoelectric underwater sound projectors. Although tone-pip and short-duration tonal stimuli may possess relatively narrow frequency bandwidth, the resulting physiological responses may possess much greater bandwidth, especially for lower frequency stimuli at higher stimulus levels. In this study, high-pass masking noise techniques were used to examine the place specificity of auditory evoked responses from click, tone-pip, and sinusoidal amplitude modulated tones in bottlenose dolphins (Tursiops truncatus). The experimental methods for generating and spectrally equalizing masking noise and click stimuli will be presented, along with the effect of compensated clicks with uncompensated clicks and ABR latencies and amplitudes. [Funded by U.S. Navy Living Marine Resources Program.]

Effect of hearing loss, age, and gender on the outcome of the cochlear hydrops analysis masking procedure.

The aims of the study are to investigate the effect of hearing loss, age, and gender on the outcome of the cochlear hydrops analysis masking procedure (CHAMP) and to assess the clinical utility of CHAMP for the diagnosis of Ménière's disease (MD). Prospective observational study. Otolaryngology department of a tertiary referral hospital. We recruited MD patients (MD, 12 subjects) and hearing loss patients (HL, 10 subjects). Control subjects (NC, 43 subjects) were matched for gender and age. CHAMP was performed in the patients and control subjects. The mean difference in latency between the wave V for the click alone response and wave V for the 0.5-kHz high-pass masking noise condition was compared among groups, and the effects of gender and age on the results were analyzed in the NC group. Both the MD group and the HL group had a smaller difference in latency compared to the NC group. The MD group and HL group showed no significant difference in latency. In the NC group, there were no significant differences in latency depending on gender and age. Hearing level seems to significantly affect the CHAMP results, making it unreliable to differentiate between MD patients and non-MD hearing loss patients. Therefore, the diagnostic value of CHAMP might be limited in MD.

Subcortical representation of musical dyads: Individual differences and neural generators

When two notes are played simultaneously they form a musical dyad. The sensation of pleasantness, or “consonance”, of a dyad is likely driven by the harmonic relation of the frequency components of the combined spectrum of the two notes. Previous work has demonstrated a relation between individual preference for consonant over dissonant dyads, and the strength of neural temporal coding of the harmonicity of consonant relative to dissonant dyads as measured using the electrophysiological “frequency-following response” (FFR). However, this work also demonstrated that both these variables correlate strongly with musical experience. The current study was designed to determine whether the relation between consonance preference and neural temporal coding is maintained when controlling for musical experience. The results demonstrate that strength of neural coding of harmonicity is predictive of individual preference for consonance even for non-musicians. An additional purpose of the current study was to assess the cochlear generation site of the FFR to low-frequency dyads. By comparing the reduction in FFR strength when high-pass masking noise was added to the output of a model of the auditory periphery, the results provide evidence for the FFR to low-frequency dyads resulting in part from basal cochlear generators.

Effects of the intensity of masking noise on ear canal recorded low-frequency cochlear microphonic waveforms in normal hearing subjects

Compared to auditory brainstem responses (ABRs), cochlear microphonics (CMs) may be more appropriate to serve as a supplement to the test of otoacoustic emissions (OAEs). Researchers have shown that low-frequency CMs from the apical cochlea are measurable at the tympanic membrane using high-pass masking noise. Our objective is to study the effect of such noise at different intensities on low-frequency CMs recorded at the ear canal, which is not completely known. Six components were involved in this CM measurement including an ear canal electrode (1), a relatively long and low-frequency toneburst (2), and high-pass masking noise at different intensities (3). The rest components include statistical analysis based on multiple human subjects (4), curve modeling based on amplitudes of CM waveforms (CMWs) and noise intensity (5), and a technique based on electrocochleography (ECochG or ECoG) (6). Results show that low-frequency CMWs appeared clearly. The CMW amplitude decreased with an increase in noise level. It decreased first slowly, then faster, and finally slowly again. In conclusion, when masked with high-pass noise, the low-frequency CMs are measurable at the human ear canal. Such noise reduces the low-frequency CM amplitude. The reduction is noise-intensity dependent but not completely linear. The reduction may be caused by the excited basal cochlea which the low-frequency has to travel and pass through. Although not completely clear, six mechanisms related to such reduction are discussed.

How is periodicity pitch encoded on basilar membrane of the cochlea?

Pitch is the perceptual correlate of periodicity of sound. Even if all the energy at the fundamental frequency (F0) is removed, a periodic complex tone retains the same pitch of missing fundamental frequency. The periodicity pitch has been mostly discussed in the central auditory system while less reported in the peripheral system. The purpose of this study was to investigate how the periodicity pitch is encoded in the cochlea. Cochlear microphonics (CM) was recorded from the round window for confirming frequency characteristics of vibration of the basilar membrane (BM) to periodic complex tones in order to generate F0. The experiments were carried out in the condition which a frequency component corresponding to F0 or frequency components of the sound stimuli were masked by low or high frequency band pass noises respectively. The forward masking did not have temporal overlap of the sound stimuli on the BM. The results showed that the frequency component of F0 existed in the CM. The frequency component of F0 decreased for high frequency band pass masking but little for low frequency band pass masking. The findings suggest that the periodicity pitch is encoded using rates of amplitude modulation rather than the location on the BM.

A comparison of electrocochleography and high-pass noise masking of auditory brainstem response for diagnosis of Ménière's disease

Objective: To study differences between electrocochleography (ECochG) and cochlear hydrops analysis masking procedure (CHAMP) in diagnosis of Ménière's disease. Design: Retrospective case review from a tertiary referral center. Study sample: Thirty patients suspected to have Ménière's disease were assessed by ECochG and CHAMP tests. Results: Positivity of ECochG with SP/AP amplitude ratio >.40 or >.35 was compared with CHAMP V-delay or CHAMP R × D. Positive ECochG results were found in 43% (>.40 SP/AP ratio) and 63% (>.35 SP/AP ratio) of patients, comparing to positive CHAMP V delay in 27% and CHAMP R × D in 30% of patients. A significant difference (p <.01) was found between ECochG and CHAMP in diagnostic sensitivity. Also, a positive inter-aural correlation was found in CHAMP results (p <.003), but not in ECochG (p =.082) results. Conclusions: ECochG is a more sensitive test than CHAMP in detecting the presence of endolymphatic hydrops in Ménière's patients. CHAMP covaried interaurally in unilateral Ménière's patients whereas ECochG did not.

Mapping auditory nerve firing density using high-level compound action potentials and high-pass noise masking

Future implementation of regenerative treatments for sensorineural hearing loss may be hindered by the lack of diagnostic tools that specify the target(s) within the cochlea and auditory nerve for delivery of therapeutic agents. Recent research has indicated that the amplitude of high-level compound action potentials (CAPs) is a good predictor of overall auditory nerve survival, but does not pinpoint the location of neural damage. A location-specific estimate of nerve pathology may be possible by using a masking paradigm and high-level CAPs to map auditory nerve firing density throughout the cochlea. This initial study in gerbil utilized a high-pass masking paradigm to determine normative ranges for CAP-derived neural firing density functions using broadband chirp stimuli and low-frequency tonebursts, and to determine if cochlear outer hair cell (OHC) pathology alters the distribution of neural firing in the cochlea. Neural firing distributions for moderate-intensity (60 dB pSPL) chirps were affected by OHC pathology whereas those derived with high-level (90 dB pSPL) chirps were not. These results suggest that CAP-derived neural firing distributions for high-level chirps may provide an estimate of auditory nerve survival that is independent of OHC pathology.

Study of characteristic of the cochlear hydrops analysis masking procedure in normal adults

To study the characteristic of the cochlear hydrops analysis masking procedure (CHAMP) in normal adults, and to evaluate the diagnostic values of its parameters for membranous labyrinth hydrops. Twenty otologically normal adults were recruited (male:female = 10:10), and their auditory brainstem responses (ABR) were obtained to six stimulus conditions using Bio-logic auditory evoked potential system: clicks presented alone (unmasked condition) and clicks presented with ipsilateral pink noise high-pass filtered at 8, 4, 2, 1, and 0.5 kHz respectively. The wave V latency of ABR to the high-pass masking pink noise clicks were longer than ABR to clicks alone. The latency delays of wave V for clicks presented with ipsilateral pink noise high-pass filtered at 8, 4, 2, 1, and 0.5 kHz compared to clicks alone were (0.30 ± 0.18), (0.97 ± 0.43), (1.65 ± 0.64), (3.21 ± 0.56), (4.66 ± 0.37) ms respectively. The complex amplitude ratio between ABR to click + 0.5 kHz high-pass noise and click alone was 0.95 ± 0.11. CHAMP is a promising diagnostic method for membranous labyrinth hydrops, and the latency delay of wave V might be used as the normal criterion. The specificity of the complex amplitude ratio need further evaluation in clinical work.

Scale dependence and channel switching in letter identification

Letters are broadband visual stimuli with information useful for discrimination over a wide range of spatial frequencies. Yet, recent evidence suggests that observers use only a single, fixed spatial-frequency channel to identify letters and that the scale of that channel, in units of letter size, is determined by the size of the letter (scale dependence). We report two letter-identification experiments using critical-band masking. With sufficiently high-amplitude, low- or high-pass masking noise, observers switched to a different range of spatial frequencies for the task. Thus, letter channels are not fixed for a given letter size. When an additional white-noise masker was added to the stimulus to flatten the contrast-sensitivity function, the letter channel used by the observer still depended on letter size, further supporting the hypothesis that letter identification is scale dependent.

RESPONSE TO "LACK OF DIAGNOSTIC VALUE OF HIGH-PASS NOISE MASKING OF AUDITORY BRAINSTEM RESPONSES IN MÉNIÈRE'S DISEASE BY CLAUDIA F. J. DE VALCK, GERD M. E. CLAES, FLORIS L. WUYTS, AND PAUL H. VAN DE HEYNING. OTOLOGY &amp; NEUROTOLOGY 2007;28:700-7"

In the recent paper “Lack of Diagnostic Value of High-Pass Noise Masking of Auditory Brainstem Responses in Meniere’s Disease” by De Valck et al. (2007), the authors concluded that, due to its low sensitivity (31%) and low specificity (28%), the ABR high-pass noise masking technique (Don et al., 2005), commercially known as CHAMP (Natus/Bio-logic Corp.), had “…no discriminative value in differentiating Meniere’s from non-MD subjects with otovestibular symptoms” (p. 706). In reviewing their data and analyses, we found errors that led to misleading and inappropriate conclusions. This response will briefly review the errors and suggest that once these errors are corrected, the revised values of 100% sensitivity and 80% specificity are consistent with the excellent sensitivity and specificity described in the original paper (Don et al., 2005). Before discussing the errors, it is important to note that the authors state, “…when only definite MD patients were included, and only the interpretable tests were used, a 100% sensitivity was obtained as in the study of Don et al. (11).” (p.705) In addition, they state, “…none of our definite MD patients had a test within normal ranges.” (p. 706) Thus, as in our study (Don et al., 2005), these authors found that in all the patients with definite Meniere’s disease (MD) and measurable responses, the test results were abnormal. So, what errors led De Valck et al. (2007) to their erroneous conclusion about the value of the CHAMP test?

Can the binaural system extract fine-structure interaural time differences from noncorresponding frequency channels?

Due to the phase differences in the basilar membrane response between neighboring places along the cochlea, it is generally assumed that the processing of interaural time differences (ITDs) in the temporal fine structure relies on comparisons between corresponding frequency channels from the two ears. This study was aimed to test whether the auditory system is capable of extracting fine-structure ITDs from noncorresponding channels. For that, the ITD discrimination threshold was measured for a 500 Hz pure tone partially masked by a lowpass masker in one ear and a highpass masker in the other. The maskers were intended to obscure the apical or basal part of the tone's excitation pattern, respectively, and thus force the listener to extract ITDs from disparate channels. While the results did not allow any definite conclusions as to whether or not ITD processing in these conditions was based on cross-channel comparisons, some aspects of the data suggest that it was. Modeling simulations showed that any cross-channel comparisons would have to be limited to a fairly narrow frequency range of little more than one auditory-filter bandwidth. However, the between-channel phase differences within even such a narrow range would be sufficient to explain ITD sensitivity in neurophysiological data.

An Alternative Diagnostic Test for Active Ménière’s Disease and Cochlear Hydrops Using High-Pass Noise Masked Responses: The Complex Amplitude Ratio

We [Don et al.: Otol Neurotol 2005;26:711–722] previously demonstrated that patients diagnosed with an active case of Ménière’s disease could be distinguished from non-Ménière’s normal-hearing subjects by a special auditory brainstem response method involving clicks and ipsilateral high-pass masking pink noise. Specifically, auditory brainstem responses to clicks presented alone and clicks with masking noise high-pass filtered at 8, 4, 2, 1 and 0.5 kHz were recorded. It was shown that the level of masking noise sufficient to progressively mask the response to clicks in non-Ménière’s normal-hearing subjects was insufficient to appropriately mask the responses in Ménière’s disease subjects, resulting in an obvious undermasked component. A relative latency measure of wave V or the undermasked component in the response to clicks with 0.5 kHz high-pass masking noise and wave V in the response to clicks presented alone clearly distinguished these two groups on an individual level, thus making it a valuable clinical tool. However, determining the peak latency of wave V or the undermasked component can be difficult in some cases. In anticipation of this difficulty, we investigated and present in this paper several amplitude measures that may help in the evaluation of these cases. One amplitude measure, the ‘complex amplitude ratio’, appears to be a good alternative when the latency measure of the undermasked component is difficult to determine.

Lack of Diagnostic Value of High-Pass Noise Masking of Auditory Brainstem Responses in M??ni??re's Disease

Lack of Diagnostic Value of High-Pass Noise Masking of Auditory Brainstem Responses in M??ni??re's Disease

Interactive Effects of High-Pass Filtering and Masking Noise on Word Recognition

This study sought to examine the word recognition performance in noise of individuals with a simulated low-frequency hearing loss. The goal was to understand how low-frequency hearing impairment affects performance on tasks that challenge temporal processing skills. Twenty-two normal-hearing young adults participated. Monosyllabic words were presented in continuous and interrupted noise at 3 signal-to-noise ratios of -10, 0, and +10 dB. High-pass filtering of the stimuli at 3 different cutoff frequencies (ie, 1,000, 1,250, and 1,500 Hz) simulated the low-frequency hearing impairment. In general, performance decreased with increasing cutoff frequency, was higher for more favorable signal-to-noise ratios, and was superior in the interrupted condition relative to the continuous noise condition. One important revelation was that the magnitude of the performance superiority observed in the interrupted noise condition did not diminish with high-pass filtering; ie, the release from masking in interrupted noise was preserved. The results of the present study complement previous findings in which this paradigm was used with low-pass filtering to simulate a high-frequency hearing loss. That is to say, low-frequency hearing channels are inherently poorer than high-frequency channels in temporal resolution.

Monaural and interaural intensity discrimination: level effects and the "binaural advantage".

This study examined whether the level effects seen in monaural intensity discrimination (Weber's law and the "near miss") in a two-interval task are also observed in discrimination of interaural intensity differences (IIDs) in a single-interval task. Both tasks were performed for various standard levels of 4-kHz pure tones and broadband noise. The Weber functions (10 log deltaI/I versus I in dB) in the monaural and binaural conditions were parallel. For noise, the Weber functions had slopes close to zero (Weber's law) while the Weber functions for the tones had a mean slope of -0.089 (near miss). The near miss for the monaural and binaural tasks with tones was eliminated when a high-pass masker was gated with the listening intervals. The near-miss was also observed for 250- and 1000-Hz tones in the binaural task despite overall decreased sensitivity to changes in IID at 1000 Hz. The binaural thresholds showed a small (about 2-dB) advantage over monaural thresholds only in the broadband noise conditions. More important, however, is the fact that the level effects seen monaurally are also seen binaurally. This suggests that the basic mechanisms responsible for Weber's law and the near miss are common to monaural and binaural processing.

The role of call frequency and the auditory papillae in phonotactic behavior in male Dart-poison frogs Epipedobates femoralis (Dendrobatidae).

Territorial males of the pan-Amazonian Dart-poison frog, Epipedobates femoralis, are known to present stereotypic phonotactic responses to the playback of conspecific and synthetic calls. Fixed site attachment and a long calling period within an environment of little temperature change render this terrestrial and diurnal pan-Amazonian frog a rewarding species for field bioacoustics. In experiments at the field station Aratai, French Guiana, we tested whether the prominent frequency modulation of the advertisement-call notes is critical for eliciting phonotactic responses. Substitution of the natural upward sweep by either a pure tone within the species frequency range or a reverse sweep did not alter the males' phonotactic behavior. Playbacks with artificial advertisement calls embedded in high levels of either low-pass or high-pass masking noise designed to saturate nerve fibers from either the amphibian papilla or basilar papilla showed that male phonotactic behavior in this species is subserved by activation of the basilar papilla of the inner ear.

Effects of Decreased Audibility Produced by High-Pass Maskers in Younger and Older Adults

A recurring problem in aging research is separating the effects of age per se from the effects of high-frequency hearing loss. One approach is to present test stimuli in the presence of a high-pass masker to control confounding differences in high-frequency audibility across age groups. However, there is evidence that such maskers may affect older and younger listeners differently. In this study, pure-tone thresholds were measured for younger and older listeners in the presence of high-pass maskers. The age groups were carefully selected based on similar unmasked thresholds at each frequency. Thresholds were measured in quiet and in seven masker conditions. Both younger and older listeners showed increased threshold shift below the masker passband as the masker level increased. The degree of threshold shift was not greater for older versus younger listeners. Results suggest that high-pass maskers may be used to reduce high-frequency sensitivity differences between younger and older listeners without introducing differential masking effects.