Edward Cudahy

Frequency discrimination in the presence of another tone

The effects of an interference tone on frequency discrimination of a brief tonal signal were investigated. The interference tone was 500 msec in duration and the same intensity as the signal. Changes in frequency discrimination were measured as a function of signal duration, the frequency separation between the interference tone and signal, and the temporal delay between the two. Both ipsilateral‐ and contralateral‐interference conditions were investigated. The addition of an interference tone significantly degraded preformance in only one condition: 10‐msec signal, trailing interference tone delivered to signal ear. For all other stimulus configurations, frequency discrimination was unaffected by the presence of the interference tone. These data are generally consistent with analogous sensory masking effects characterizing backward and forward masking and do not support cognitive‐perceptual models of pitch and recognition.

Intensity discrimination for pulsed sinusoids of various frequencies

Studies of pure-tone intensity discrimination have shown that Weber’s law fails for tones in the region of 1 kHz. In this experiment, intensity discrimination of pulsed sinusoids ranging in frequency from 0.15 to 12 kHz is investigated. For each tone in this region, Weber’s law is found to fail. Some theoretical implications of these results are discussed.

Critical masking interval: a temporal analog of the critical band

The critical masking interval, the time period during which noise is effective in masking a brief click, was measured in two independent experiments. The first paradigm was the temporal analog of Fletchers critical band experiment. That is, the click was presented in the temporal center of the noise, and its threshold was measured as the masker duration was varied. The second paradigm investigated the temporal analog of Greenwoods [J. Acoust. Soc. Am. 33, 484–502 (1961a)] masking experiment; that is, a click was moved temporally through the noise burst. The two paradigms yielded similar numerical estimates of the critical masking interval. Further, the critical masking interval was not greatly affected by the stimulus bandwidth.

Masking with Continuous and Gated Sinusoids

The detection of a 5‐msec tonal signal presented at various delays after the onset of a 500‐msec tonal masker was investigated in several transient‐masking experiments. Changes in the amount of masking were measured as a function of the delay between onset of the signal and the onset of the longer‐duration masker. In agreement with previous investigations of transient masking there was a large decrease in masked threshold, 26 dB in some conditions, with an increase in signal delay. A “transient overshoot” at masker termination was also noted. These data are consistent with a short‐time energy‐sensing model of detection. In a second transient‐masking study, the masking produced by a gated sinusoid in the presence of a continuous tonal pedestal was investigated. The pedestal results indicate that a simple, linear, time‐invariant, energy‐detection scheme cannot account for the results of two‐tone masking experiments.

Effects of a contralateral interference tone on auditory recognition

The effects of a contralateral interference tone on identification of the frequency of a brief signal were investigated. The signal was a 20-reset sinusoid and was the same intensity as the 500-msec interference tone. Changes in frequency discrimination were measured as a function of the temporal intee, al between rdgnal and interference tone. Frequency discrimination was unaffected by the presence of a leading interference torte. However, the addition of a trailing interference tone produced a small (about 15%) decrement in performance relative to discriminability measured in quiet. In contrast to the data and supporting theory of Massaro (1970) percent correct identification did not vary appreciably with intertone interval. The present data suggest that interference effects previously obtained with untrained Os ;are greatly attenuated for well-practiced Ss

Masking patterns for continuous and gated sinusoids

The masking of a brief tonal signal by continuous and gated sinusoids was investigated. Masking patterns depicting the threshold of a signal of frequency fs as a function of masker frequency fm for the two masker presentations were compared. In the frequency region fm ≳ fs, the briefly presented gates masker was always a more effective masker than the continuous steady‐state background, even under conditions in which energy spread of the gated masker was minimized. For fm < fs, the gated–continuous threshold shift, sometimes called the ’’overshoot,’’ reversed when a low‐level background noise was added to the tonal nasker in order to mask audible combination tones. The presence of combination tones in the steady‐state masker condition precluded application of a simple energy detection model in the frequency region fm < fs. An attempt to simulate the results for fm ≳ fs with an energy‐detection scheme in conjunction with a detailed spectral analysis of the stimuli was also unsuccessful.Subject Classificati...

The effect of masker duration on forward and backward masking

Temporal masking of clicks by noise was investigated using forward and backward masking paradigms. Both the noise duration and the temporal separation, ΔT, between the click and noise were varied. For very brief ΔTs (100 microsec) and for very long ΔTs (100 msec), the duration of the masker did not greatly affect the click threshold. However, for intermediate ΔTs (3 msec), the threshold increased by as much as 44 dB as the noise duration increased from 0.1 to 100 msec. Temporal weighting functions, which describe the relative effectiveness of the noise as a function of ΔT, were computed from these data.

Temporal processing in noise by persons with noise‐induced and age‐related hearing loss

A variety of tasks, using a 21FC procedure, were employed to investigate auditory temporal processing in noise by hearing‐impaired and normal listeners. First, temporal integration functions were measured in wide‐band noise for tonal durations ranging from 3 to 985 msec at 500, 1500, 2000, and 4000 Hz. Second, detectability in the presence of a continuous narrowband (400–800 Hz) noise masker was measured for 5‐ and 146‐msec tonal signals at six frequencies from 500 to 4000 Hz. Finally, forward masking, backward masking, and gap masking were studied for a 5‐msec 1500‐Hz signal and a narrow‐band (400–800) noise masker. For gap masking, the masker was continuous except for a brief silence or “gap” of 20‐, 50‐, or 200‐msec duration during each observation interval. Several general trends emerged from the data. First, all hearing‐impaired subjects showed poorer than normal temporal integration at frequencies where their audiometric loss was greater than 40 dB. Second, listeners with noise‐induced hearing loss ...

Temporal masking patterns for hearing‐impaired and normal listeners

Forward masking, backward masking, and gap masking were employed to investigate temporal processing by hearing‐impaired and normal listeners. Masked thresholds for a 5‐reset 2500‐Hz tonal signal in the presence of a narrow‐band (1175–1725 Hz) noise masker were measured with a 21FC procedure. (This study represents an extension of previous work in a lower frequency region.) In the gap masking conditions, the noise was on continuously except for a brief silence, or “gap,” of 200‐, 50‐, or 20 msec. In general, hearing‐impaired listeners had less steep backward masking functions than did the normal Ss. They also showed less decrease in masking during the gap. As the duration of the gap decreased, the difference in the gap masking patterns between normal and hearing‐impaired Ss increased. The implications of these results for temporal processing by hearing‐impaired listeners will be discussed.

Backward and forward masking in normal and hearing‐impaired listeners

Backward‐ and forward‐masking patterns for a 10‐msec probe with a 10‐msec masker were measured for normal and hearing‐impaired listeners in a 2IFC adaptive procedure. The probe and masker were equal in frequency. In previous work masker level has been kept constant and probe level has been varied. The present study employed a procedure analogous to psychophysical tuning curve measurements, i.e., probe level was kept at a constant sensation level and masker level was varied. Masker level at masked threshold was measured as a function of delay of prove relative to masker for probe sensation levels of 10 and 30 dB and for probe frequencies of 1 and 3 kHz. In general, hearing‐impaired Ss showed broader than normal masking patterns in both backward‐ and forward‐masking conditions at both signal levels. Masking patterns narrowed for both groups of Ss as signal level was increased. Some possible implications of these results for temporal processing by hearing‐impaired listeners will be discussed.