ПОРОГОВАЯ И НАДПОРОГОВАЯ МАСКИРОВКА ГРОМКОСТИ ТЕСТОВЫХ ИМПУЛЬСОВ, ВЫЗВАННАЯ ПЕРИОДИЧЕСКОЙ ПОСЛЕДОВАТЕЛЬНОСТЬЮ ИМПУЛЬСОВ

Abstract

In order to search for indicators of temporal processing of periodic sounds, we studied the effect of the periodicity of a train of masking pulses on the temporal resolution and masking of the loudness of the test pulse, which was the first or the last in the train. Measurements were carried out on listeners with normal hearing and age-related sensorineural hearing loss. The test pulse delay D relative to the train was equal to the pulse repetition period T in the train (D = T). The center frequencies and frequency bands of all pulses were 4 kHz and 240 Hz. Under such conditions, the basis for detecting test pulses was believed to be their loudness. The intensity of masking pulses Im was 80 dB SPL. The period T was varied within the range of 20–150 ms while the test pulse intensity Is within the range of 0–85 dB. The temporal resolution of the pulse loudness was equal to the minimum period Tmin, at which the listener could detect a test pulse. Threshold masking of the test pulse loudness (Is ≪ Im) corresponded to the shift in the test pulse detection threshold, SIО, obtained in the train presence relative to the threshold obtained in silence. If intensities of the masking and test pulses were equal, the latest pulse could not be detected, but the test pulse could be detected by increasing or decreasing its intensity. Thus, supra-threshold masking of the test pulse loudness (Is ∼ Im) was estimated by the shifts, SdIU and SdID, in the threshold intensity decrement and increment of the masked test pulse relative to the threshold intensity increment of a single masking pulse. It was shown that it is only SIO and SdID that were related to the temporal resolution of the test pulses loudness. These shifts depended both on the test pulse position relative to the train and auditory sensitivity of the listeners. The largest SIO and SdID shifts were recorded at the temporal resolution threshold of the test pulse loudness, i.e. at T min. For listeners with normal hearing, Tmin was 25 ms, while SIO and SdID shifts were 12 and 18 dB if the test pulse was ahead of the train and 23 and 0 dB if the test pulse followed the train. In listeners with age-related hearing loss, the Tmin period increased up to 80–150 ms. At T of 120 ms, SIО and SdID shifts were 1 and 4 dB if the test pulse was ahead of the train and 4 and 7 dB if the test pulse followed the train. The informational significance of the Tmin, SIО and SdID indicators was confirmed by their manifestations in the profiles oftest pulse detection threshold dependences on the test pulse delay D (D ≠ T). The Tmin, SIО and SdID indicators could be the characteristics of the temporal perception of periodic sounds, including speech. The causes of threshold and supra-threshold masking of the test pulse loudness at different positions of the test pulse relative to the masking pulse train are discussed.