Temporal loudness weights: Primacy effects, loudness dominance and their interaction

Loudness judgments of sounds varying in level across time show a non-uniform temporal weighting, with increased weights assigned to the beginning of the sound (primacy effect). In addition, higher weights are observed for temporal components that are higher in level than the remaining components (loudness dominance). In three experiments, sounds consisting of 100- or 475-ms Gaussian wideband noise segments with random level variations were presented and either none, the first, or a central temporal segment was amplified or attenuated. In Experiment 1, the sounds consisted of four 100-ms segments that were separated by 500-ms gaps. Previous experiments did not show a primacy effect in such a condition. In Experiment 2, four- or ten-100-ms-segment sounds without gaps between the segments were presented to examine the interaction between the primacy effect and level dominance. As expected, for the sounds with segments separated by gaps, no primacy effect was observed, but weights on amplified segments were increased and weights on attenuated segments were decreased. For the sounds with contiguous segments, a primacy effect as well as effects of relative level (similar to those in Experiment 1) were found. For attenuation, the data indicated no substantial interaction between the primacy effect and loudness dominance, whereas for amplification an interaction was present. In Experiment 3, sounds consisting of either four contiguous 100-ms or 475-ms segments, or four 100-ms segments separated by 500-ms gaps were presented. Effects of relative level were more pronounced for the contiguous sounds. Across all three experiments, the effects of relative level were more pronounced for attenuation. In addition, the effects of relative level showed a dependence on the position of the change in level, with opposite direction for attenuation compared to amplification. Some of the results are in accordance with explanations based on masking effects on auditory intensity resolution.

Probability characteristics and sensitivity of wideband noise-like signal detector with duration selectivity

Для широкополосного обнаружителя шумового сигнала с квадратором и селекторами сигнала по уровню и длительности разработана методика определения порогов селекции по уровню и длительности, если задана вероятность ложной тревоги на максимально возможном интервале ожидания сигнала. В основе методики – применение «выбросовой» вероятностной модели работы обнаружителя в режиме ожидания и использование многомерной функции распределения вероятностей нормализованного помехового индикаторного процесса. Получена вероятностная характеристика обнаружения и изложена методика оценки чувствительности двухселекторного обнаружителя. Показано, что применение селекции по длительности позволяет повысить чувствительность двухселекторного обнаружителя по сравнению с односелекторным при равной вероятности ложной тревоги. Показано, что существует оптимальное сочетание порогов селекции по уровню и длительности, когда критерием оптимальности является максимум чувствительности обнаружителя. Этот максимум достигается, когда порог селекции по длительности составляет 0.1 от периода средней квадратичной частоты флуктуаций помехового индикаторного процесса. This article proposes a method for determining the level and duration thresholds in a wideband noise-like signal detector if the probability of a false alarm is set at the maximum possible signal waiting interval. The method is based on the use of «emissional» probabilistic model of the detector in standby mode and the use of a multidimensional probability distribution function of the normalized noise indicator process. A probabilistic characteristic of detection is obtained and also described a technique for the estimation of sensitivity of a two-step selection detector. It is shown that the use of selection by duration makes possible to increase the sensitivity of a two-step selection detector in comparison with a single-step selection detector with an equal probability of a false alarm. It is shown that there is an optimal combination of selection thresholds in terms of level and duration, when the optimality criterion is the maximum sensitivity of the detector. This maximum is reached when the duration selection threshold is about 0.1 of the period of the root-mean-square fluctuations frequency of the noise indicator process.