Henoch-Schönlein purpura with severe ileal involvement responding to plasmapheresis.
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Adult↗
Biomedical subjects
H Gaskell
Publications and source records attributed to H Gaskell.
The precedence effect.
When two similar transient sounds are presented binaurally in rapid succession, observers hear a single sound from a location which depends mainly on the properties of the first sound to reach the ears. This phenomenon, known as the precedence effect, was explored using stimuli consisting of 20 mus pulses presented using earphones; experiments were carried out on both the classical precedence effect (in which interaural delays provide the cues to lateralization) and on an amplitude-based precedence effect, where interaural amplitude differences provide the cues. Some experiments on the amplitude-based precedence effect led to unexpected but highly consistent anomalous results. The spectral characteristics of stimuli used in studies of both the classical and amplitude-based precedence effect were considered and, provided the delay between the two pairs of pulses used in the experiments is 600 mus or less, observers' behaviour is simply related to the amplitude and phase spectra of the stimuli.
Acoustic Stimulation↗
The effect of noise on time-intensity trading in lateralization.
A two-interval forced-choice lateralization task was used to determine interaural delays and interaural amplitude ratios which, when opposed in quiet, led to chance lateralization; the opposed cues formed time-intensity trades. Three types of signal were used: (1) 20-microseconds clicks; (2) 250-ms bursts of a 305 Hz tone; and (3) 250-ms bursts of 3965 Hz carrier amplitude modulated to a depth of 100% at a modulation rate of 305 Hz. The addition of various levels of broad-band white noise did not influence the relative effectiveness of the two lateralization cues with pure tone signals; however, the addition of noise to clicks and to AM waveforms led to lateralization judgements in which the cue based on interaural delay appeared to be less effective than in quiet.
Acoustic Stimulation↗
Binaural masking level differences with a variety of waveforms.
Binaural masking level differences (BMLDs) were measured in a standard two-interval forced-choice detection task. The signals were (a) 250-ms bursts of pure tones, (b) amplitude-modulated waveforms with either high- or low-frequency carriers, and (c) 20-microseconds clicks. The pure tones and clicks were presented either eith zero phase difference between the ears or with an 180 degrees phase difference between the ears: the AM tones were presented in several different interaural phase conditions, only some of which lead to changes in the apparent location of the signal source. The noise against which all the signals were detected was white, broad-band, and identical at the ears. BMLDs were invariably small with high-frequency signals and with clicks. Although the magnitude of the BMLD obtained with low-frequency signals appeared to be related to the Observers' ability to lateralize the signal, there is a simpler explanation based on the assumption that detection of low-frequency AM signals is determined by independent detection of its components.
Acoustic Stimulation↗