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Andrew J Oxenham - One of the best experts on this subject based on the ideXlab platform.
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auditory enhancement under Forward Masking in normal hearing and hearing impaired listeners
Journal of the Acoustical Society of America, 2019Co-Authors: Heather A. Kreft, Andrew J OxenhamAbstract:A target within a spectrally notched masker can be enhanced by a preceding copy of the masker. Enhancement can also increase the effectiveness of the target as a Forward masker. Enhancement has been reported in hearing-impaired listeners under simultaneous but not Forward Masking. However, previous studies of enhancement under Forward Masking did not fully assess the potential effect of differences in sensation level or spectral resolution between the normal-hearing and hearing-impaired listeners. This study measured enhancement via Forward Masking in hearing-impaired and age-matched normal-hearing listeners with different spectral notches in the masker, to account for potential differences in frequency selectivity, and with levels equated by adding a background Masking noise to equate both sensation level and sound pressure level or by reducing the sound pressure level of the stimuli to equate sensation level. Hearing-impaired listeners showed no significant enhancement, regardless of spectral notch width. Normal-hearing listeners showed enhancement at high levels, but showed less enhancement when sensation levels were reduced to match those of the hearing-impaired group, either by reducing sound levels or by adding a Masking noise. The results confirm a lack of Forward-masked enhancement in hearing-impaired listeners but suggest this may be partly due to reduced sensation level.
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Auditory Enhancement in Cochlear-Implant Users Under Simultaneous and Forward Masking
Journal of the Association for Research in Otolaryngology, 2017Co-Authors: Heather A. Kreft, Andrew J OxenhamAbstract:Auditory enhancement is the phenomenon whereby the salience or detectability of a target sound within a masker is enhanced by the prior presentation of the masker alone. Enhancement has been demonstrated using both simultaneous and Forward Masking in normal-hearing listeners and may play an important role in auditory and speech perception within complex and time-varying acoustic environments. The few studies of enhancement in hearing-impaired listeners have reported reduced or absent enhancement effects under Forward Masking, suggesting a potentially peripheral locus of the effect. Here, auditory enhancement was measured in eight cochlear-implant (CI) users with direct stimulation. Masked thresholds were measured under simultaneous and Forward Masking as a function of the number of Masking electrodes, and the electrode spacing between the maskers and the target. Evidence for auditory enhancement was obtained under simultaneous Masking, qualitatively consistent with results from normal-hearing listeners. However, no significant enhancement was observed under Forward Masking, in contrast to earlier results with normal-hearing listeners. The results suggest that the normal effects of auditory enhancement are partially but not fully experienced by CI users. To the extent that the CI users’ results differ from normal, it may be possible to apply signal processing to restore the missing aspects of enhancement.
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behavioral estimates of basilar membrane compression additivity of Forward Masking in noise masked normal hearing listeners
Journal of the Acoustical Society of America, 2011Co-Authors: Melanie J Gregan, Peggy B Nelson, Andrew J OxenhamAbstract:Cochlear hearing loss is often associated with a loss of basilar-membrane (BM) compression, which in turn may contribute to degraded processing of suprathreshold stimuli. Behavioral estimates of compression may therefore be useful as long as they are valid over a wide range of levels and frequencies. Additivity of Forward Masking (AFM) may provide such a measure, but research to date lacks normative data from normal-hearing (NH) listeners at high sound levels, which is necessary to evaluate data from hearing-impaired (HI) listeners. The present study measured AFM in six NH listeners for signal frequencies of 500, 1500, and 4000 Hz in the presence of background noise, designed to elevate signal thresholds to levels similar to those experienced by HI listeners. Results consistent with compressive BM responses were found for all six listeners at 500 Hz, five listeners at 1500 Hz, but only two listeners at 4000 Hz. Further measurements in the absence of background noise also indicated a lack of consistent com...
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recovery from on and off frequency Forward Masking in listeners with normal and impaired hearing
Journal of the Acoustical Society of America, 2010Co-Authors: Magdalena Wojtczak, Andrew J OxenhamAbstract:The aim of this study was to investigate the possible mechanisms underlying an effect reported earlier [Wojtczak, M., and Oxenham, A. J. (2009). J. Acoust. Soc. Am. 125, 270–281] in normal-hearing listeners, whereby recovery from Forward Masking can be slower for off-frequency tonal maskers than for on-frequency tonal maskers that produce the same amount of Masking at a 0-ms masker-signal delay. To rule out potential effects of confusion between the tonal signal and tonal masker, one condition used a noise-band Forward masker. To test whether the effect involved temporal build-up, another condition used a short-duration (30-ms) Forward masker. To test whether the effect is dependent on normal cochlear function, conditions were tested in five listeners with sensorineural hearing loss. For the 150-ms noise maskers, the data from normal-hearing listeners replicated the findings from the previous study that used tonal maskers. In contrast, no significant difference in recovery from on- and off-frequency Masking was observed for the 30-ms tonal maskers in normal-hearing listeners, or for the 150-ms tonal maskers in hearing-impaired listeners. Overall, the results are consistent with a mechanism based on efferent feedback that affects the recovery from Forward Masking in the normal auditory system.
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On- and Off-Frequency Forward Masking by Schroeder-Phase Complexes
Journal of the Association for Research in Otolaryngology, 2009Co-Authors: Magdalena Wojtczak, Andrew J OxenhamAbstract:Forward Masking by harmonic tone complexes was measured for on- and off-frequency maskers as a function of masker phase curvature for two masker durations (30 and 200 ms). For the lowest signal frequency (1 kHz), the results matched predictions based on the expected interactions between the phase curvature and amplitude compression of peripheral auditory filtering. For the higher signal frequencies (2 and 6 kHz), the data increasingly departed from predictions in two respects. First, the effects of the masker phase curvature became stronger with increasing masker duration, inconsistent with the expected effects of the fast-acting compression and time-invariant phase response of basilar membrane filtering. Second, significant effects of masker phase curvature were observed for the off-frequency masker using a 6-kHz signal, inconsistent with predictions based on linear processing of stimuli well below the signal frequency. New predictions were generated assuming an additional effect with a longer time constant, consistent with the influence of medial olivocochlear efferent activation on otoacoustic emissions in humans. Reasonable agreement between the predicted and the measured effects suggests that efferent activation is a potential candidate mechanism to explain certain spectro-temporal Masking effects in human hearing.
Enrique A Lopezpoveda - One of the best experts on this subject based on the ideXlab platform.
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Forward Masking recovery and the assumptions of the temporal Masking curve method of inferring cochlear compression
Trends in hearing, 2014Co-Authors: Enrique A Lopezpoveda, Patricia Perezgonzalez, Peter T JohannesenAbstract:The temporal Masking curve (TMC) method is a behavioral technique for inferring human cochlear compression. The method relies on the assumptions that in the absence of compression, Forward-Masking recovery is independent of masker level and probe frequency. The present study aimed at testing the validity of these assumptions. Masking recovery was investigated for eight listeners with sensorineural hearing loss carefully selected to have absent or nearly absent distortion product otoacoustic emissions. It is assumed that for these listeners basilar membrane responses are linear, hence that Masking recovery is independent of basilar membrane compression. TMCs for probe frequencies of 0.5, 1, 2, 4, and 6 kHz were available for these listeners from a previous study. The dataset included TMCs for masker frequencies equal to the probe frequencies plus reference TMCs measured using a high-frequency probe and a low, off-frequency masker. All of the TMCs were fitted using linear regression, and the resulting slope and intercept values were taken as indicative of Masking recovery and masker level, respectively. Results for on-frequency TMCs suggest that Forward-Masking recovery is generally independent of probe frequency and of masker level and hence that it would be reasonable to use a reference TMC for a high-frequency probe to infer cochlear compression at lower frequencies. Results further show, however, that reference TMCs were sometimes shallower than corresponding on-frequency TMCs for identical probe frequencies, hence that compression could be overestimated in these cases. We discuss possible reasons for this result and the conditions when it might occur.
Albert S Berrebi - One of the best experts on this subject based on the ideXlab platform.
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Forward Masking in the superior paraolivary nucleus of the rat
Brain Structure and Function, 2017Co-Authors: Fei Gao, Alexandra Kadner, Richard A. Felix, Liang Chen, Albert S BerrebiAbstract:In natural acoustic environments, perception of acoustic stimuli depends on the recent contextual history. Forward Masking describes a phenomenon whereby the detection threshold of a probe stimulus is markedly increased when it is preceded by a Masking stimulus. The aim of this study was to characterize the offset response of single units in the superior paraolivary nucleus (SPON) to a Forward Masking paradigm. We observed two distinct response types to Forward-masked stimuli, namely inhibited and facilitated responses. In the presence of a default Masking stimulus, inhibited responses to probe stimuli were characterized by elevated thresholds and/or diminished spike counts, whereas facilitated responses were characterized by reduced thresholds and increased spike counts. In units with inhibited responses to the probe stimuli, probe thresholds increased and spike counts decreased as masker intensity was raised or the masker-to-probe delay was shortened. Conversely, in units with facilitated responses to the probe stimuli, probe thresholds decreased and spike counts increased as masker intensity was raised or the masker-to-probe delay was shortened. Neither inhibited nor facilitated responses to the Forward Masking paradigm were significantly dependent on masker frequency. These findings suggest that SPON responses are not themselves consistently subject to the same Forward Masking properties observed in other nuclei along the ascending auditory pathway. The potential neural mechanisms of the Forward Masking responses observed in the SPON are discussed.
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Forward Masking in the medial nucleus of the trapezoid body of the rat
Brain Structure & Function, 2016Co-Authors: Albert S BerrebiAbstract:Perception of acoustic stimuli is modulated by the temporal and spectral relationship between sound components. Forward Masking experiments show that the perception threshold for a probe tone is significantly impaired by a preceding masker stimulus. Forward Masking has been systematically studied at the level of the auditory nerve, cochlear nucleus, inferior colliculus and auditory cortex, but not yet in the superior olivary complex. The medial nucleus of the trapezoid body (MNTB), a principal cell group of the superior olive, plays an essential role in sound localization. The MNTB receives excitatory input from the contralateral cochlear nucleus via the calyces of Held and innervates the ipsilateral lateral and medial superior olives, as well as the superior paraolivary nucleus. Here, we performed single-unit extracellular recordings in the MNTB of rats. Using a Forward Masking paradigm previously employed in studies of the inferior colliculus and auditory nerve, we determined response thresholds for a 20-ms characteristic frequency pure tone (the probe), and then presented it in conjunction with another tone (the masker) that was varied in intensity, duration, and frequency; we also systematically varied the masker-to-probe delay. Probe response thresholds increased and response magnitudes decreased when a masker was presented. The Forward suppression effects were greater when masker level and masker duration were increased, when the masker frequency approached the MNTB unit’s characteristic frequency, and as the masker-to-probe delay was shortened. Probe threshold shifts showed an exponential decay as the masker-to-probe delay increased.
Brian C J Moore - One of the best experts on this subject based on the ideXlab platform.
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frequency selectivity in the modulation domain estimated using Forward Masking effects of masker modulation depth and masker signal delay
Hearing Research, 2021Co-Authors: Christian Fullgrabe, Aleksander Sek, Brian C J MooreAbstract:The threshold for detecting amplitude modulation (AM) of a sinusoidal or noise carrier is elevated when the signal AM is preceded by masker AM applied to the same carrier. This effect, called AM Forward Masking, shows selectivity in the AM domain, consistent with the existence of a modulation filter bank (MFB). In this paper we explore the effect of two factors that can influence AM Forward Masking, using an 8-kHz sinusoidal carrier and a range of masker AM frequencies, fm, both below and above the signal AM frequency, fs, of 40 Hz. The first factor was the time delay, td, between the end of the masker AM and the start of the signal AM. The second was the AM depth, m, of the masker, which was either 1 or 0.25. The AM Forward Masking patterns in all conditions showed tuning in the AM domain; signal thresholds were highest when fm was close to fs. The amount of AM Forward Masking decreased with increasing td in a similar way for all fm, so the shapes of the Masking patterns did not change markedly with td. Remarkably, the amount of AM Forward Masking decreased by only about 3 dB (a non-significant effect) when the masker m was decreased from 1 to 0.25. This result appears to be inconsistent with an explanation of AM Forward Masking in terms of adaptation in a MFB or in terms of a sliding temporal integrator.
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Forward Masking of amplitude modulation across ears and its tuning in the modulation domain
Journal of the Acoustical Society of America, 2021Co-Authors: Christian Fullgrabe, Aleksander Sek, Brian C J MooreAbstract:Frequency selectivity in the amplitude modulation (AM) domain has been demonstrated using both simultaneous AM Masking and Forward AM Masking. This has been explained using the concept of a modulation filter bank (MFB). Here, we assessed whether the MFB occurs before or after the point of binaural interaction in the auditory pathway by using Forward Masking in the AM domain in an ipsilateral condition (masker AM and signal AM applied to the left ear with an unmodulated carrier in the right ear) and a contralateral condition (masker AM applied to the right ear and signal AM applied to the left ear). The carrier frequency was 8 kHz, the signal AM frequency, fs, was 40 or 80 Hz, and the masker AM frequency ranged from 0.25 to 4 times fs. Contralateral Forward AM Masking did occur, but it was smaller than ipsilateral AM Masking. Tuning in the AM domain was slightly sharper for ipsilateral than for contralateral Masking, perhaps reflecting confusion of the signal and masker AM in the ipsilateral condition when their AM frequencies were the same. The results suggest that there might be an MFB both before and after the point in the auditory pathway where binaural interaction occurs.
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detecting dead regions using psychophysical tuning curves a comparison of simultaneous and Forward Masking
International Journal of Audiology, 2006Co-Authors: Karolina Kluk, Brian C J MooreAbstract:A dead region (DR) is a region of the cochlea where there are no functioning inner hair cells and/or neurones. We compared the edge frequencies, fe, of DRs estimated using four methods: the TEN(HL) test; psychophysical tuning curves (PTCs) measured in simultaneous Masking (320-Hz wide noise masker) using a 'fast' method (sweeping masker) and a 'classical' method; and PTCs measured in Forward Masking (sinusoidal masker) using a 'classical' method. Fourteen subjects with high-frequency DRs were tested. For measurement of PTCs, the signal frequency was chosen to fall inside the DR; the tip frequencies of the PTCs were taken as indicating the values of fe. The values of fe obtained from the PTCs in Forward and simultaneous Masking (both fast and classical methods) were similar and were usually close to, but somewhat above, the values of fe estimated from the TEN(HL) test. Fast PTCs measured in simultaneous Masking are recommended for use in clinical practice, as they give a precise estimate of fe and are quick to administer.
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effects of masker component phase on the Forward Masking produced by complex tones in normally hearing and hearing impaired subjects
Hearing Research, 2004Co-Authors: Brian C J Moore, Thomas H Stainsby, Esme TarasewiczAbstract:For normally hearing subjects, harmonic complex tones that give "peaky" waveforms on the basilar membrane (Schroeder-positive phase, sine phase or cosine phase) lead to less Forward Masking than complex tones that give less peaky waveforms (Schroeder-negative phase or random phase), but have the same power spectrum. This difference has been attributed mainly to the combined effects of peripheral compression and suppression, both of which depend on the operation of the active mechanism in the cochlea. If this explanation is correct, the phase effect should be reduced or absent for subjects with moderate cochlear hearing loss. We measured growth-of-Masking functions for Forward maskers containing the first 40 harmonics of a 100-Hz fundamental, with components added either in cosine phase or random phase, using both normally hearing subjects and subjects with moderate cochlear hearing loss. The signal frequency was 1 or 2 kHz. For the normally hearing subjects, the mean slopes of the growth-of-Masking functions at 1 and 2 kHz, respectively, were 0.53 and 0.44 for the random-phase masker and 0.31 and 0.26 for the cosine-phase masker. For high masker levels, the former produced considerably more Masking than the latter. The phase effect was smaller for the hearing-impaired than for the normally hearing subjects, which is consistent with the idea that it is partly caused by peripheral compression and suppression. However, three of the five hearing-impaired subjects showed a significant effect of masker phase for at least one signal frequency. In one case, this occurred when the hearing loss at the signal frequency was 65 dB. The slopes of the growth-of-Masking functions were consistently less than one for the hearing-impaired subjects. Further testing suggested that the efferent system was not involved in producing the phase effect.
Laurel H. Carney - One of the best experts on this subject based on the ideXlab platform.
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Modeling Responses in the Superior Paraolivary Nucleus: Implications for Forward Masking in the Inferior Colliculus.
Journal of the Association for Research in Otolaryngology : JARO, 2017Co-Authors: Nima Salimi, Muhammad S. A. Zilany, Laurel H. CarneyAbstract:A phenomenological model of the responses of neurons in the superior paraolivary nucleus (SPON) of the rodent is presented in this study. Pure tones at the characteristic frequency (CF) and broadband noise stimuli evoke offset-type responses in these neurons. SPON neurons also phase-lock to the envelope of sinusoidally amplitude-modulated (SAM) stimuli for a range of modulation frequencies. Model SPON neuron received inhibitory input that was relayed by the ipsilateral medial nucleus of the trapezoid body from the contralateral model ventral cochlear nucleus neuron. The SPON model response was simulated by detecting the slope of its inhibitory postsynaptic potential. Responses of the proposed model to pure tones at CF and broadband noise were offset-type independent of the duration of the input stimulus. SPON model responses were also synchronized to the envelope of SAM stimuli with precise timing for a range of modulation frequencies. Modulation transfer functions (MTFs) obtained from the model response to SAM stimuli resemble the physiological MTFs. The output of the proposed SPON model provides an input for models of physiological responses at higher levels of the ascending auditory pathway and can also be utilized to infer possible mechanisms underlying gap detection and duration encoding as well as Forward Masking at the level of the auditory midbrain.
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Forward Masking in the Amplitude-Modulation Domain for Tone Carriers: Psychophysical Results and Physiological Correlates
Journal of the Association for Research in Otolaryngology, 2011Co-Authors: Magdalena Wojtczak, Neal F Viemeister, Paul C. Nelson, Laurel H. CarneyAbstract:Wojtczak and Viemeister (J Acoust Soc Am 118:3198–3210, 2005 ) demonstrated Forward Masking in the amplitude-modulation (AM) domain. The present study examined whether this effect has correlates in physiological responses to AM at the level of the auditory midbrain. The human psychophysical experiment used 40-Hz, 100% AM (masker AM) that was imposed on a 5.5-kHz carrier during the first 150 ms of its duration. The masker AM was followed by a 50-ms burst of AM of the same rate (signal AM) imposed on the same (uninterrupted) carrier, either immediately after the masker or with a delay. In the physiological experiment, single-unit extracellular recordings in the awake rabbit inferior colliculus (IC) were obtained for stimuli designed to be similar to the uninterrupted-carrier conditions used in the psychophysics. The masker AM was longer (500 ms compared with 150 ms in the psychophysical experiment), and the carrier and modulation rate were chosen based on each neuron’s audio- and envelope-frequency selectivity. Based on the average discharge rates of the responses or on the temporal correlation between neural responses to masked and unmasked stimuli, only a small subset of the population of IC cells exhibited suppression of signal AM following the masker. In contrast, changes in the discharge rates between the temporal segments of the carrier immediately preceding the signal AM and during the signal AM varied as a function of masker-signal delay with a trend that matched the psychophysical results. Unless the physiological observations were caused by species differences, they suggest that stages of processing higher than the IC must be considered to account for the AM-processing time constants measured perceptually in humans.