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...
Auditory temporal masking and the perception of order.
An investigation of the effects of frequency, intensity, and time on the perception of temporal order and the amount of temporal masking produced under conditions of a short burst (12 msec) of tone separated temporally from a narrow‐band noise indicates a similarity of function underlying the two phenomena. Temporal masking is greater and the perception of temporal order is more difficult when the signal is centered in the band of noise. Temporal masking is greater and the perception of temporal order is more difficult for a weak signal than for a more intense signal. The observed temporal masking can be interpreted in terms of a cochlear model. The relationship between temporal masking and the perception of temporal order is discussed in terms of a hierarchy of level of perception brought about by temporal cues.
Control of the homopause level
Abstract This paper reviews the hypothesis that internal gravity wave breaking in the factor responsible for upper atmosphere turbulence generation and control of the number density at the homopause level. Available data from Mars and Earth support the hypothesis, originally introduced by Lindzen, that breaking thermal tides are responsible for the necessary turbulence. The lowest-order, equatorially trapped, westward-propagating diurnal tidal mode is the primary cause on the Earth, and lower-order westward-propagating semidiurnal modes are the primary cause on Mars. The frequencies and vertical wavenumbers of the responsible modes determine the eddy diffusion coefficients; energy density is only indirectly involved by determining which modes can break. A general scale relationship between tidal heating and velocity amplitude can be used to assess the breaking potential of tidal modes, and is used here as the basis for arguing that the number density at the Martian homopause is likely to have been stable over much of geologic time. Difficulties with this approach arise in the cases of Venus and Titan because of their peculiar zonal winds. For Jupiter and Saturn, internal gravity waves generated by nontidal mechanisms probably control the homopause.