Temporal integration as a funtion of masker bandwidth

Thresholds were measured for a 6-kHz sinusoid, temporally centered in a 500-ms masker which was either a bandpass Gaussian noise (20 dB SPL spectrum level) or a 6-kHz sinusoid (40 dB SPL). A notched noise centered on 6 kHz prevented the use of off-frequency cues. The signal, gated with 2-ms ramps, ranged in half-amplitude duration from 2 to 300 ms. The noise bandwidth was arithmetically centered on 6 kHz and was varied from 60 Hz to 12 kHz. For masker bandwidths below 300 Hz, the slope of integration for signal durations between 2 and 20 ms decreased with decreasing masker bandwidth. For the tonal masker, increasing signal duration from 2 to 20 ms had no effect on threshold. These results cannot be accounted for by lowpass-filter or temporal-window models of temporal integration or resolution. Instead, it is proposed that the auditory system performs a spectral analysis of the stimulus envelope, so that the rapid fluctuations (high modulation frequencies) introduced by gating the signal can be used as a cue for brief signals in narrowband noise and tones. For broadband maskers, this cue is not available due to the masker's inherent rapid envelope fluctuations. [Work supported by the Wellcome Trust.

Heart-Kidney Interaction: Epidemiology of Cardiorenal Syndromes

Cardiac and kidney diseases are common, increasingly encountered, and often coexist. Recently, the Acute Dialysis Quality Initiative (ADQI) Working Group convened a consensus conference to develop a classification scheme for the CRS and for five discrete subtypes. These CRS subtypes likely share pathophysiologic mechanisms, however, also have distinguishing clinical features, in terms of precipitating events, risk identification, natural history, and outcomes. Knowledge of the epidemiology of heart-kidney interaction stratified by the proposed CRS subtypes is increasingly important for understanding the overall burden of disease for each CRS subtype, along with associated morbidity, mortality, and health resource utilization. Likewise, an understanding of the epidemiology of CRS is necessary for characterizing whether there exists important knowledge gaps and to aid in the design of clinical studies. This paper will provide a summary of the epidemiology of the cardiorenal syndrome and its subtypes

Increment and decrement detection as a measure of auditory temporal resolution

The temporal resolution of the auditory system, or its ability to follow rapid fluctuations, is fundamental to the processing of all acoustic stimuli, including speech. A popular method of determining temporal resolution is to measure thresholds for detecting a brief decrement in the level of an otherwise continuous sinusoid. Background noise is often added in such experiments in order to mask 'spectral splatter'. Current models assume that detection is achieved if the maximum 'dip' in a smoothed internal representation of the stimulus exceeds a certain criterion level. The experiment described here was designed to test these models. Thresholds were measured for several durations of increments as well as decrements using a wide range of background-noise levels. Two important aspects of the results are not consistent with current models. Firstly, at short durations, there was a large asymmetry between increments and decrements; decrements were less easily detected than increments. Secondly, results were highly dependent on the level of the background noise. The data show the need for a revision of current models of temporal resolution, and cast doubt on the suitability of decrement detection as a measure of temporal resolution

Temporal integration as a funtion of masker bandwidth

Thresholds were measured for a 6-kHz sinusoid, temporally centered in a 500-ms masker which was either a bandpass Gaussian noise (20 dB SPL spectrum level) or a 6-kHz sinusoid (40 dB SPL). A notched noise centered on 6 kHz prevented the use of off-frequency cues. The signal, gated with 2-ms ramps, ranged in half-amplitude duration from 2 to 300 ms. The noise bandwidth was arithmetically centered on 6 kHz and was varied from 60 Hz to 12 kHz. For masker bandwidths below 300 Hz, the slope of integration for signal durations between 2 and 20 ms decreased with decreasing masker bandwidth. For the tonal masker, increasing signal duration from 2 to 20 ms had no effect on threshold. These results cannot be accounted for by lowpass-filter or temporal-window models of temporal integration or resolution. Instead, it is proposed that the auditory system performs a spectral analysis of the stimulus envelope, so that the rapid fluctuations (high modulation frequencies) introduced by gating the signal can be used as a cue for brief signals in narrowband noise and tones. For broadband maskers, this cue is not available due to the masker's inherent rapid envelope fluctuations. [Work supported by the Wellcome Trust.

Temporal integration at 6 kHz as a function of masker bandwidth

Thresholds were measured for a 6-kHz sinusoidal signal presented within a 500-ms masker. The masker was either a bandpass Gaussian noise of varying bandwidth, or a sinusoid of the same frequency as the signal. The spectrum level of the noise masker was kept constant at 20 dB SPL, and the level of the sinusoidal masker was 40 dB SPL. Thresholds for signal durations between 2 and 300 ms were measured for masker bandwidths ranging from 60 to 12 000 Hz. The masker was spectrally centered around 6 kHz. For masker bandwidths less than 600 Hz, the slope of the temporal integration function decreased with decreasing masker bandwidth. The results are not consistent with current models of temporal integration or temporal resolution. It is suggested that the results at narrow bandwidths can be understood in terms of changes in the power spectrum of the stimulus envelope or modulation spectrum. According to this view, the onset and offset ramps of the signal introduce detectable high-frequency components into the modulation spectrum, which provide a salient cue in narrowband maskers. For broadband maskers, these high-frequency components are masked by the inherent rapid fluctuations in the masker envelope. Additionally, for signal durations between 7 and 80 ms, signal thresholds decreased by up to 5 dB as the masker bandwidth increased from 1200 to 12 000 Hz. The mechanisms underlying this effect are not yet fully understood

Increment and decrement detection as a measure of auditory temporal resolution

The temporal resolution of the auditory system, or its ability to follow rapid fluctuations, is fundamental to the processing of all acoustic stimuli, including speech. A popular method of determining temporal resolution is to measure thresholds for detecting a brief decrement in the level of an otherwise continuous sinusoid. Background noise is often added in such experiments in order to mask 'spectral splatter'. Current models assume that detection is achieved if the maximum 'dip' in a smoothed internal representation of the stimulus exceeds a certain criterion level. The experiment described here was designed to test these models. Thresholds were measured for several durations of increments as well as decrements using a wide range of background-noise levels. Two important aspects of the results are not consistent with current models. Firstly, at short durations, there was a large asymmetry between increments and decrements; decrements were less easily detected than increments. Secondly, results were highly dependent on the level of the background noise. The data show the need for a revision of current models of temporal resolution, and cast doubt on the suitability of decrement detection as a measure of temporal resolution

Psychophysical consequences of peripheral auditory nonlinearity

SIGLEAvailable from British Library Document Supply Centre-DSC:D197925 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Modeling the effects of peripheral nonlinearity in listeners with normal and impaired hearing

Recent physiological studies of basilar rnembrane (BM) mechanics indicate that the response to tones presented at the characteristic frequency (CF) is nonlinear and cornpressive. Input-output functions show marked compression at medium input levels and become more linear at very low and very high levels. Damage to the cochlea, in particular the outer hair celis, generally results in a loss of sensitivity and a linearization of the BM transfer function. In this study we assume that listeners with cochlear hearing loss also exhibit reduced BM compression, and we investigate some possible psychoacoustic consequences of the reduced nonlinearity. Results from nonsimultaneous rnasking experiments in norrnally hearing listeners were modeled using a temporal window model, preceded by a compressive nonlinearity (Oxenham & Moore, 1994). When modeling sirnilar data from hearing-impaired listeners, only the input nonlinearity of the model was changed. The results suggest that the change in nonlinearity may be sufficient to account for some differences in performance in the additivity of nonsimultaneous masking, the decay of forward masking with increasing masker-signal interval, and the growth of forward masking with increasing masker level