Estimates of internal templates for the detection of sequential tonal patterns.

In this experiment, listeners detected sequential tonal patterns embedded in multitone multiburst random maskers. The maskers consisted of eight 30 ms bursts of random-frequency tones. The signal, when present, occupied the central six bursts and was centered at 1000 Hz. The six sequential signal tones formed several spectro-temporal patterns: an equal-frequency pattern, three ascending patterns with frequency ranges spanning 0.5-, 1-, and 2-equivalent rectangular bandwidths (ERBs), and a random pattern with frequencies drawn at random from the range of 925-1075 Hz. The total number of tones in each burst, m, was varied to determine detection threshold. The detectability of the signal pattern declined as the frequency range of the signal pattern increased, and when the signal was random. Relative weights as a function of time and frequency, interpreted as listeners' internal templates, depended systematically on the properties of the signal pattern tested. The templates indicated that when sensitivity was poor, listeners integrated increasingly broad spectro-temporal regions around the signal frequencies, and sometimes integrated energy from the final burst even though the signal tones never occupied the final burst.