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The Maximum Tolerable Delay (MTD) was measured for speech and music and was found to be one-third the repetition rate of the syllables or notes. The maximum tolerable delay increases slightly for positive echo intensity levels and increases moderately for negative echo intensity levels. The maximum tolerable delay does not exist for echo intensity levels of +14 dB and greater and -14 dB and smaller. Total sound pressure level and echo angle of incidence do not affect the maximum tolerable delay. Drum taps proved to be the most convenient test signal. The results obtained with headphones were almost identical to those obtained with loudspeaker systems.