Temporal masking-level differences: the effect of mask duration.
Psychometric functions were obatained for the interaural conditions NoSo and NoSπ in both forward and backward masking using masks of different durations. In addition, data were collected for the Sm, Sπ and So conditions without an external mask. The slope parameter k and the signal level required for 76% correct detection were computed with a least‐squares technique. The results were that both temporal masking and temporal masking‐level differences (MLDs) increased monotonically with longer mask durations. This mask‐duration effect was more pronounced for forward masking than for backward masking. Without an external mask, the signal was about 3 dB more detectable in the So configuration than in the Sπ configuration, and it was about 4 dB more detectabe in the Sπ configuration than in the Sm configuration. The psychometric functions were generally steeper for the NoSπ condition than for the NoSo condition in forward masking, but not in backward masking. They were also steeper for the Sπ condition than fo...
Masking of tone by tone as a function of duration.
A 500‐Hz tonal signal was masked by a continuous tone, both from the same oscillator. A two‐interval‐forced‐choice procedure was used to determine the level required for 80% correct. The masker level was 50 dB SPL, and the signal was always in phase with the masker. Signal durations from 20 msec to 2 sec were employed. The results showed a slope of approximately 3 dB per doubling over the entire range from 20 msec to 1 sec. Detection at 2 sec tended to be worse than at 1 sec. The slope of 3 dB per doubling is much steeper than has commonly been found with noise maskers, especially at the longer durations. Data from an electrical model are discussed.
Continuous calibration of a vacuum ultraviolet system from 65 to 125 nm by a cascade arc and comparison with the calibrated line radiation of a hollow cathode.
A high-power stationary helium cascade arc has been developed as a standard source for continuum radiation in the VUV spectral range from 65 to 125 nm. The calibration of the VUV system response was based on the calculated and measured continuum radiation of a 2-mmphi pure He arc. Diagnostics of the arc plasma in partial thermal equilibrium yielded the electron density and the temperature that were inserted in the calculations of the continuous radiation. The results were compared with the helium, argon, and krypton radiation lines of a high-current hollow cathode lamp. This lamp was built according to the construction drawings of a hollow cathode, which was calibrated by means of the electron synchrotron radiation at the Physikalisch Technische Bundesanstalt Berlin.