Geometrical interpretation of the expression for .

<p>In each panel, the thick, magenta curve represents the transducer function. The horizontal axes represent the transducer input, and the vertical axes represent the transducer output. is the pedestal level, and is the discrimination threshold. The gradient of the blue line, , is equal to <i>V</i>, defined in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0074815#pone.0074815.e230" target="_blank">Equation (39</a>). The green line is the tangent to the transducer at point ; its gradient is equal to <i>U</i>, defined in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0074815#pone.0074815.e229" target="_blank">Equation (38</a>). The ratio is equal to . For an expansive transducer (panel A), , so . For a compressive transducer (panel B), , so . For a linear transducer (panel C), , so .