Bandpass Noise Research Articles

The gap-startle paradigm for tinnitus screening in animal models: Limitations and optimization

In 2006, Turner and colleagues (Behav. Neurosci., 120:188–195) introduced the gap-startle paradigm as a high-throughput method for tinnitus screening in rats. Under this paradigm, gap detection ability was assessed by determining the level of inhibition of the acoustic startle reflex produced by a short silent gap inserted in an otherwise continuous background sound prior to a loud startling stimulus. Animals with tinnitus were expected to show impaired gap detection ability (i.e., lack of inhibition of the acoustic startle reflex) if the background sound containing the gap was qualitatively similar to the tinnitus pitch. Thus, for the gap-startle paradigm to be a valid tool to screen for tinnitus, a robust startle response from which to inhibit must be present. Because recent studies have demonstrated that the acoustic startle reflex could be dramatically reduced following noise exposure, we endeavored to 1) modify the gap-startle paradigm to be more resilient in the presence of hearing loss, and 2) evaluate whether a reduction in startle reactivity could confound the interpretation of gap prepulse inhibition and lead to errors in screening for tinnitus. In the first experiment, the traditional broadband noise (BBN) startle stimulus was replaced by a bandpass noise in which the sound energy was concentrated in the lower frequencies (5–10 kHz) in order to maintain audibility of the startle stimulus after unilateral high-frequency noise exposure (16 kHz). However, rats still showed a 57% reduction in startle amplitude to the bandpass noise post-noise exposure. A follow-up experiment on a separate group of rats with transiently-induced conductive hearing loss revealed that startle reactivity was better preserved when the BBN startle stimulus was replaced by a rapid airpuff to the back of the rat’s neck. Furthermore, it was found that transient unilateral conductive hearing loss, which was not likely to induce tinnitus, caused an impairment in gap prepulse inhibition as assessed with the traditional BBN gap-startle paradigm, resulting in a false-positive screening for tinnitus. Thus, the present study identifies significant caveats of the traditional gap-startle paradigm, and describes experimental parameters using an airpuff startle stimulus which may help to limit the negative consequences of reduced startle reactivity following noise exposure, thereby allowing researchers to better screen for tinnitus in animals with hearing loss.

Formerly known as inhibitory: effects of 1‐Hz rTMS on auditory cortex are state‐dependent

The major repetitive transcranial magnetic stimulation (rTMS) paradigm applied to the treatment of tinnitus has been the 1-Hz variant due to its alleged inhibitory effects. Clinical effects have, however, been hampered by great interindividual variability as well as the fact that TMS includes no explicit mechanism to modulate excitability in circumscribed regions of tonotopically organised auditory fields. Following studies showing that the effect of TMS depends on the activational state preceding the stimulation, participants were exposed to 10 min of either notch- or bandpass-filtered noise prior to 1-Hz rTMS applied to the left auditory cortex. A control group was additionally assessed using bandpass noise - albeit with subsequent sham stimulation - to assess whether effects were due to the differential sounds alone or to a genuine interaction between sound and rTMS. Electroencephalogram was recorded from 128 electrodes before and after the experimental treatment while participants performed an auditory intensity discrimination task. While state-dependency effects from the behavioural data are not conclusive, several condition × (sound) frequency effects (some specific to the stimulated side) could be observed. Importantly, many of these could not be explained by the use of rTMS or the filtered noise alone. The resulting patterns are, however, complex and temporally variable, which currently prohibits recommendations on how to design a clinically effective approach to treat tinnitus. Nevertheless, our study gives the first evidence that state-dependency principles can induce sound frequency-specific effects in the auditory cortex, providing a crucial proof-of-principle upon which future studies can build.

Application of Hilbert–Huang transform based instantaneous frequency to seismic reflection data

Abstract Empirical mode decomposition (EMD) is designed to decompose non-stationary, nonlinear data into a series of intrinsic mode functions (IMFs) adaptively. This procedure is automatic, data-driven and time-variant. And then a Hilbert transform is applied to these IMFs. The combination of EMD with a Hilbert transform is known as Hilbert–Huang transform (HHT). HHT can be used to calculate meaningful multi-resolution instantaneous frequency (HHT based instantaneous frequency). Currently, the application of EMD and HHT to seismic data is performed mainly for noise attenuation. In this paper, we demonstrate new insights of EMD and HHT to seismic data analysis. We first extend the research of Flandrin et al. and analyze how EMD behaves on a Gaussian band-pass signal; we then employ HHT based instantaneous frequency on wedge model and real seismic data to delineate thickness variations. Numerical examples of Gaussian band-pass noise indicate that EMD acts as an adaptive, multi-band overlapping filter bank. The analysis of a wedge model and 2D real seismic data illustrates that HHT based instantaneous frequency is more effective than conventional Hilbert transform based instantaneous frequency in delineating the thickness variation of seismic thin bed.

Frequency discrimination under conditions of comodulation masking release (L)

Masked detection thresholds can often be improved by introducing coherent masker amplitude modulation across frequency, a phenomenon referred to as comodulation masking release (CMR). While CMR can be large for detection, it is smaller for supra-threshold tasks, such as intensity discrimination. In this experiment, frequency discrimination for a 1000-Hz tone near threshold was found to be poorer in an amplitude-modulated than a steady bandpass noise. These results parallel previous findings for intensity discrimination. Although this study examined the relatively simple task of frequency discrimination, the results may have implications for more complex tasks, such as speech recognition in fluctuating noise.

Inhibition of Oscillation in a Neural Oscillator Model for Sound Therapy of Tinnitus

Perception of continuous or intermittent sounds ringing in the ears without any external source is referred to as tinnitus. For the management of tinnitus one of the most effective approaches is sound therapy. Previously, we demonstrated a conceptual and computational plastic neural oscillator model for the mechanisms of tinnitus generation and the clinical effects of sound therapy on tinnitus. The proposed model has a stable oscillatory state and a stable equilibrium (non-oscillatory) state. It can be hypothesized that the oscillation state corresponds to the generation of tinnitus and the equilibrium state corresponds to the state in which the tinnitus is inhibited. Through numerical simulations of this model it was found that the oscillation can be inhibited by supplying band-pass noise (BN) stimuli, which clinically has been used as a stimulus for treatment of tinnitus (i.e., sound therapy). The current paper describes the inhibition of the oscillation by yet two different types of noise stimuli: Gaussian white noise (GWN) and additive uniform noise (AUN). This investigation shows that only smaller RMS value of GWN input could inhibit the oscillation. When larger RMS values of GWN were employed the inhibition of oscillation was not frequent. It was observed that AUN can inhibit the oscillation with higher possibility than GWN or BN. It is an interesting result although it does not directly suggest that AUN is better than GWN or BN in clinic.

Recovery of stereopsis through perceptual learning in human adults with abnormal binocular vision

Stereopsis, the perception of depth based on the disparity of the images projected to the retinas of the two eyes, is an important process in our three-dimensional world; however, 3-5% of the population is stereoblind or has seriously impaired stereovision. Here we provide evidence for the recovery of stereopsis through perceptual learning, the repetitive practice of a demanding visual task, in human adults long deprived of normal binocular vision. We used a training paradigm that combines monocular cues that were correlated perfectly with the disparity cues. Following perceptual learning (thousands of trials) with stereoscopic gratings, five adults who initially were stereoblind or stereoanomalous showed substantial recovery of stereopsis, both on psychophysical tests with stimuli that contained no monocular cues and on clinical testing. They reported that depth "popped out" in daily life, and enjoyed 3D movies for the first time. After training, stereo tests with dynamic random-dot stereograms and band-pass noise revealed the properties of the recovered stereopsis: It has reduced resolution and precision, although it is based on perceiving depth by detecting binocular disparity. We conclude that some human adults deprived of normal binocular vision can recover stereopsis at least partially.

Functional Correlates of the Anterolateral Processing Hierarchy in Human Auditory Cortex

Converging evidence supports the hypothesis that an anterolateral processing pathway mediates sound identification in auditory cortex, analogous to the role of the ventral cortical pathway in visual object recognition. Studies in nonhuman primates have characterized the anterolateral auditory pathway as a processing hierarchy, composed of three anatomically and physiologically distinct initial stages: core, belt, and parabelt. In humans, potential homologs of these regions have been identified anatomically, but reliable and complete functional distinctions between them have yet to be established. Because the anatomical locations of these fields vary across subjects, investigations of potential homologs between monkeys and humans require these fields to be defined in single subjects. Using functional MRI, we presented three classes of sounds (tones, band-passed noise bursts, and conspecific vocalizations), equivalent to those used in previous monkey studies. In each individual subject, three regions showing functional similarities to macaque core, belt, and parabelt were readily identified. Furthermore, the relative sizes and locations of these regions were consistent with those reported in human anatomical studies. Our results demonstrate that the functional organization of the anterolateral processing pathway in humans is largely consistent with that of nonhuman primates. Because our scanning sessions last only 15 min/subject, they can be run in conjunction with other scans. This will enable future studies to characterize functional modules in human auditory cortex at a level of detail previously possible only in visual cortex. Furthermore, the approach of using identical schemes in both humans and monkeys will aid with establishing potential homologies between them.

Zur objektiven Beurteilung der Zischlautbildung

The inaccurate production of 's-sounds', i. e. sibilants represents the most common speech disorder. An objective description of such inaccurate speech sound production is mandatory. Several tools have been proposed and might be of great value, amongst them spectral analysis. The latter can nowadays be performed easily without the need for expensive equipment. Different sibilants were uttered either as isolated speech sounds or embedded in test words and sentences. These were then digitized and spectral analysis was performed. Since several protocols have been put forward on how to execute the spectral analysis of sibilants, we replicated those protocols and evaluated how they exert influence on the analysis results. The selection of time windows or frequency bands regarding the computation of spectral moments will be considered in particular. Sibilants are characterised by a band-pass noise. Usage of power spectral density functions for the extraction of features from temporal and spatial signals is a standard approach. Thus, we calculated spectral moments to describe noise signals derived from sibilant productions. We demonstrate differing results based on varying frequency and time analysis windows. Unfortunately to date there is no generally accepted "gold standard" for the spectro analysis of speech sounds. For clinical routine, we recommend using a time window of 40 ms around the temporal midpoint, extracted from utterances or words. It is important, however, that recording conditions and analysis parameters are identical pre- and post therapy.

A Gerbil Model of Sloping Sensorineural Hearing Loss

The goal of the overall project is to develop knowledge about cochlear physiology during cochlear implantation and develop procedures for assessing its status during hearing preservation surgery. As a step toward this goal, for this study, we established an animal model of sloping high frequency sensorineural hearing loss that mimics the hearing condition of candidates for combined electric-acoustic stimulation. Mongolian gerbils were exposed to band-pass noise using various cutoff frequencies, intensities, exposure times, and survival times. Hearing loss was assessed in far-field recording using preexposure and postexposure auditory brainstem responses (ABRs), and in acute, near-field recordings of the cochlear microphonic and compound action potential from an electrode on the round window. Anatomic loss of hair cells was assessed from dissections. Postexposure ABRs and near-field recordings from the round window revealed sensorineural hearing loss that varied with the overall noise exposure. Loss of hair cells ranged from relatively sparse to large areas of complete absence depending on the noise exposure. Cases with high intensity (120 dB SPL) and long exposure times (3 h) showed sloping patterns of hearing loss with profound high-frequency loss and mild-to-moderate low-frequency loss. These cases showed complete loss of hair cells in the basal cochlea and preserved hair cells in the apical cochlea. The frequencies comprising the slope in the ABRs and the location of the transition zone between preserved and lost hair cells varied according to the cutoff frequency used. We were able to reliably induce sensorineural hearing loss and loss of hair cells in the gerbil that is comparable to candidates for hearing preservation surgery. This model can be used to evaluate the effects of electrode introduction in a system with a hearing condition similar to that in cases of hearing preservation operations.

Auditory cortical tuning to band-pass noise in primate A1 and CM: A comparison to pure tones

We examined multiunit responses to tones and to 1/3 and 2/3 octave band-pass noise (BPN) in the marmoset primary auditory cortex (A1) and the caudomedial belt (CM). In both areas, BPN was more effective than tones, evoking multiunit responses at lower intensity and across a wider frequency range. Typically, the best responses to BPN remained at the characteristic frequency. Additionally, in both areas responses to BPN tended to be of greater magnitude and shorter latency than responses to tones. These effects are consistent with the integration of more excitatory inputs driven by BPN than by tones. While it is generally thought that single units in A1 prefer narrow band sounds such as tones, we found that best responses for multi units in both A1 and CM were obtained with noises of narrow spectral bandwidths.

Speech perception in steady and amplitude modulated band-pass noise.

The purpose of the current study was to examine the effects of temporal and spectral interferences on sentence recognition for cochlear (CI) implant listeners. Nie and Nelson (2010) investigated vocoded speech perception in amplitude-modulated band-pass noises in order to assess young normal-hearing (NH) listeners’ speech understanding through cochlear implant simulations. They reported that while the spectra of the noise bands affected vocoder speech perception, there was no significant effect of the noise AM rate on performance, indicating spectral but not temporal interference. As a follow-up, young CI listeners with various devices and processing strategies participated in the current study. IEEE sentences and white noise were divided into 16 bands, and band-pass noise maskers were formed from varying combinations of 4–6 adjacent bands. The spectra of the maskers relative to the spectra of speech were set to be one of the following: completely overlapping, partially overlapping or completely separate from the speech. Noise was sinusoidally modulated at three rates: 4, 16, and 32 Hz. It is hypothesized that sentence recognition scores for CI listeners are affected by both spectral and temporal characteristics of the noise, which is different from the performance for NH listeners reported previously.

Age‐related changes in the binaural temporal window.

Substantial data indicate that monaural temporal processing, sound localization ability, and spatial release from masking decline with advancing age. Physiological and psychophysical evidence indicate that the auditory system is quite sensitive to patterns of interaural cross correlation (IACC) as determined by the combined input from the two ears. Here we test the hypothesis that age‐related changes in temporal processing lead to an elongation of the binaural temporal window as measured with an interaural correlation change interval (ICCI) task. The ICCI threshold was measured as a function of the duration change in interaural correlation. Band pass (400–3200 Hz) noise bursts were separated into three segments. Initial and final segments were interaurally uncorrelated while central segments were interaurally uncorrelated in the standard intervals and interaurally correlated in the signal interval. The duration of the central segment was adaptively varied to determine ICCI threshold. The just noticeable difference in static interaural correlation also was measured. The perception of static and dynamic changes in interaural correlation as well as estimates of the equivalent rectangular duration of the binaural temporal window will be compared across groups of younger and older adult subjects.

Spatial influences on the spectral restoration of narrowband speech.

In phonemic restoration, both perceived continuity and intelligibility of temporally interrupted speech improve with the addition of noise in the speech gaps. Perceived continuity decreases slightly when interrupted speech and “filler” noise are presented from different directions; however, a recent study found that intelligibility is not strongly influenced by spatial cues. A few studies have demonstrated spectral restoration: improvements in the intelligibility of speech that has spectral notches when band-passed filler noise is added to the spectral gaps. Here, we explored whether the spatial location speech and filler noise influence intelligibility in spectral restoration conditions. We tested intelligibility of two 3/4-wide speech bands in a variety of configurations. Control conditions included diotic presentation of a low-frequency speech band alone, a high-frequency band alone, and the two bands together. Intelligibility was poor for either band alone, but significantly better with the two bands together. When we added diotic noise to the spectral gap between the low- and high-frequency bands, intelligibility improved. Finally, when we presented the noise with an ITD so that it was perceived from off center, intelligibility was lower than when both filler noise and speech bands were diotic. Results demonstrate a spatial influence on spectral restoration.

Subjective evaluation of across‐frequency delays.

Basilar‐membrane filtering introduces frequency‐dependent cochlear delays. Cochlear models predict that the delay between the peaks in responses to 100‐Hz versus 10‐kHz tones may be as long as 10 ms. This study investigated the role of across‐frequency delays for asynchrony perception. A method of constant stimuli was used to evaluate the perception of delays between two tones, a 250‐Hz tone paired with a higher‐frequency tone at 1, 2, 4, or 6 kHz for a range of delays between the high‐ and low‐frequency tones. Bandpass noise located between the two tones was used to avoid within‐channel cues. Listeners judged whether the tone pairs appeared synchronous or asynchronous. For each pair, the proportion of “synchronous” responses was plotted as a function of the delay between the tones. Since cochlear‐filter bandwidths depend on level, the perception of across‐frequency delays was evaluated for two levels of the tones, 20 dB SL and 85 dB SPL. Overall, the data support the hypothesis of a higher‐level mechanis...

Correlation of neural response properties with auditory thalamus subdivisions in the awake marmoset.

As the information bottleneck of nearly all auditory input that reaches the cortex, the auditory thalamus serves as the basis for establishing auditory cortical processing streams. The functional organization of the primary and nonprimary subdivisions of the auditory thalamus is not well characterized, particularly in awake primates. We have recorded from neurons in the auditory thalamus of awake marmoset monkeys and tested their responses to tones, band-pass noise, and temporally modulated stimuli. We analyzed the spectral and temporal response properties of recorded neurons and correlated those properties with their locations in the auditory thalamus, thereby forming the basis for parallel output channels. Three medial geniculate body (MGB) subdivisions were identified and studied physiologically and anatomically, although other medial subdivisions were also identified anatomically. Neurons in the ventral subdivision (MGV) were sharply tuned for frequency, preferred narrowband stimuli, and were able to synchronize to rapid temporal modulations. Anterodorsal subdivision (MGAD) neurons appeared well suited for temporal processing, responding similarly to tone or noise stimuli but able to synchronize to the highest modulation frequencies and with the highest temporal precision among MGB subdivisions. Posterodorsal subdivision (MGPD) neurons differed substantially from the other two subdivisions, with many neurons preferring broadband stimuli and signaling changes in modulation frequency with nonsynchronized changes in firing rate. Most neurons in all subdivisions responded to increases in tone sound level with nonmonotonic changes in firing rate. MGV and MGAD neurons exhibited responses consistent with provision of thalamocortical input to core regions, whereas MGPD neurons were consistent with provision of input to belt regions.

Effects of non-simultaneous masking on the binaural masking level difference

The present study sought to clarify the role of non-simultaneous masking in the binaural masking level difference for maskers that fluctuate in level. In the first experiment the signal was a brief 500-Hz tone, and the masker was a bandpass noise (100-2000 Hz), with the initial and final 200-ms bursts presented at 40-dB spectrum level and the inter-burst gap presented at 20-dB spectrum level. Temporal windows were fitted to thresholds measured for a range of gap durations and signal positions within the gap. In the second experiment, individual differences in out of phase (NoSπ) thresholds were compared for a brief signal in a gapped bandpass masker, a brief signal in a steady bandpass masker, and a long signal in a narrowband (50-Hz-wide) noise masker. The third experiment measured brief tone detection thresholds in forward, simultaneous, and backward masking conditions for a 50- and for a 1900-Hz-wide noise masker centered on the 500-Hz signal frequency. Results are consistent with comparable temporal resolution in the in phase (NoSo) and NoSπ conditions and no effect of temporal resolution on individual observers' ability to utilize binaural cues in narrowband noise. The large masking release observed for a narrowband noise masker may be due to binaural masking release from non-simultaneous, informational masking.

Where orientation tuning arises

Introduction: The neural circuitry underlying orientation selectivity, a fundamental question in vision, remains the center of controversy. Some advocate a modified feedforward model, originating in connections from LGN to V1, while others maintain that intracortical activity plays a crucial role in shaping selectivity. To test the role of intracortical activity in shaping orientation selectivity in humans, we employed TMS to attenuate cortical responses to an oriented stimulus and used noise masking to estimate orientation-tuning curves psychophysically. Methods: Prior to each block of experimental trials, we applied TMS pulses at 1 Hz continuously for 2.5 minutes, thereby depressing neural activity at a specific retinotopic site in early visual cortex including V1. In each trial, a filtered noise patch appeared inside or outside the visual region corresponding to the TMS site. A vertically oriented Gabor was embedded within the upper or lower portion of this noise patch, for which observers performed a 2AFC location discrimination task. To obtain psychophysical tuning functions, we used an orientation-bandpass noise masking procedure in which the noise and probe ranged from being identical in orientation, to the noise orientations being orthogonal to the Gabor probe. An adaptive procedure produced estimates of contrast thresholds for the probe embedded within varying orientation bandpass noise, yielding tuning curves for conditions when the stimuli appeared within or outside of the TMS site. Results and Conclusion: Contrast thresholds were elevated for several minutes following TMS (but only at the TMS site), confirming its effectiveness at depressing neural activity at that location. Orientation-tuning bandwidths, however, were unchanged by TMS stimulation. To confirm that TMS disrupts intracortical activity, we found that TMS weakens an illusion known to involve intracortical interactions. These results imply that orientation tuning is governed largely by thalamocortical feedforward signals, with intracortical activity contributing little to the sharpness of orientation tuning.

Overshoot measured physiologically and psychophysically in the same human ears

A nonlinear version of the stimulus-frequency otoacoustic emission (SFOAE) was measured using stimulus waveforms similar to those used for behavioral overshoot. Behaviorally, the seven listeners were as much as 11 dB worse at detecting a brief tonal signal (4.0 kHz, 10 ms in duration) when it occurred soon after the onset of a wideband masking noise (0.1–6.0 kHz; 400 ms in duration) than when it was delayed by about 200 ms, and the nonlinear SFOAE measure exhibited a similar effect. When either lowpass (0.1–3.8 kHz) or bandpass noise (3.8–4.2 kHz) was used instead of the wideband noise, the physiological and behavioral measures again were similar. When a highpass noise (4.2–6.0 kHz) was used, the physiological and behavioral measures both showed no overshoot-like effect for five of the subjects. The physiological response to the tone decayed slowly after the termination of the noise, much like the time course of resetting for behavioral overshoot. One subject exhibited no overshoot behaviorally even though his cochlear responses were like those of the other subjects. Overall, the evidence suggests that some basic characteristics of overshoot are obligatory consequences of cochlear function, as modulated by the olivocochlear efferent system.

Analysis and Design of a Multistage CMOS Band-Pass Low-Noise Preamplifier for Ultrawideband RF Receiver

A CMOS low-noise preamplifier for application in a 3.1-10.6-GHz ultrawideband radio-frequency (RF) receiver system is presented. This is essentially a wideband-pass multistage RF preamplifier using a cascade of a three-segment band-pass LC ? -section filter with a common-gate stage as the front end. Fundamental design analysis in terms of gain, bandwidth, noise, and impedance matching for the amplifier is presented in detail. The preamplifier was fabricated using the low-cost TSMC 0.18-?m 6M1P CMOS process technology. The amplifier delivered a buffered power gain (S 21) of ? 14 dB with a -3-dB bandwidth (between the corner frequencies) of around 7.5 GHz. It consumed around 30 mW from a 2.5-V supply voltage. It had a minimum passband noise figure of around 4.7 dB, an input-referred third-order intercept point of -5.3 dBm, and reverse isolation (S 12) under -65 dB.

Auditory stream segregation using amplitude modulated vocoder bandpass noise.

We investigated the contribution of amplitude modulation (AM) rate and spectral separation to stream segregation of vocoder bandpass noises. Stimulus sequences were repeated pairs of A and B bursts, where bursts were white noise or vocoder bandpass noise carrying sinusoidal AM (100% modulation depth). Bursts differed either in the center frequency of the noise, or the AM rate, or both. Eight vocoder bands were used. The lowest four bands (1‐2‐3‐4) were combined into one bandpass noise (B bursts) and the higher three bands (3‐4‐5, 4‐5‐6, and 6‐7‐8) were combined to constitute the A bursts. Results show that stream segregation ability increases with greater spectral separation. Larger AM rate separations were associated with stronger segregation abilities, but not when A and B bursts were both white noise. Significant inter‐subject differences were noted. Results suggest that, while both spectral and AM rate separation separations could be cues for auditory stream segregation, stream segregation based on AM rate is more successful when combined with spectral separation. Correlations between segregation ability and understanding of vocoded speech will be discussed.