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Temporal MaskingTemporal masking occurs when a sudden stimulus sound makes inaudible other sounds which are present immediately preceding or following the stimulus. Masking that obscures a sound immediately preceding the masker is called backwards masking or pre-masking and masking that obscures a sound immediately following the masker is called forwards masking or post-masking. Temporal masking's effectiveness attenuates exponentially from the onset and offset of the masker, with the onset attenuation lasting approximately 10 ms and the offset attenuation lasting approximately 50 ms. Similar to simultaneous masking, temporal masking reveals the frequency analysis performed by the auditory system; forwards masking thresholds for complex harmonic tones (e.g., a sawtooth probe with a fundamental frequency of 500 Hz) exhibit threshold peaks (i.e., high masking levels) for frequency bands centered around the first several harmonics. In fact, auditory bandwidths measured from forwarding masking thresholds are narrower and more accurate than those measured using simultaneous masking. Temporal masking should not be confused with the ear's acoustic reflex, an involuntary response in the middle ear that is activated to protect the ear's delicate structures from loud sounds. One example of temporal masking is the illusory continuity of tones, an auditory illusion wherein a tone is interrupted by a burst of static but is perceived by the listener to be continuous.
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