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This line graph has a Y axis labelled ‘relative signal amplitude’, measured in decibels, and has points minus 80 (bottom) and 0 (top) marked.

The X axis is labelled as time, measured in milliseconds. It has points T and T plus 50 marked. A long vertical arrow, pointing upwards, is positioned at T, extending from Y equals minus 80 to Y equals 0. Four short, parallel vertical arrows are shown close to the T plus 50 position. The first is about one quarter of the length of the long arrow, the second about half the length, the third about a third of the length and the fourth about one quarter of the length of the long arrow.

The waveform starts at position minus 80 on the Y axis, at a position just before T on the X axis. It rises as a straight diagonal line, reaching its peak value of Y equals 0 just after time T. It then remains constant at a relative signal amplitude of 0 decibels until approximately T plus 30. It then drops as a smooth curve to a minimum at T plus 50.

The area under the waveform from just before time T through to time T plus 50 is shaded and labelled ‘inaudible signal amplitudes’.

 3.4 Perceptual encoding