In normal ears, threshold intensity as a function of the duration of a tonal pulse is determined. Identical results are obtained by a reciprocal determination. The reciprocal determination is made by fixing the intensity level at specified points above reference threshold to measure thetime threshold. The duration‐intensity relationship reveals a marked dependency upon frequency; the differences observed are equivalent to the alteration of loudness function for the various test frequencies. A new measure ofloudness increment degree, as well as conversion of decibel values into phon and sone values, indicates a close relationship between time threshold and loudness sensation. Therefore, the relationship between pulse duration and loudness level presents no artifacts reflecting frequency‐dependent changes. The time threshold (Tmsec), as a fraction of pulse durationrethe “adjusting time” of the auditory mechanism (150/T), seems to indicate the loudness of related levels above threshold in sones. General conclusions deriving from these relationships and some limitations of their applicability are discussed in detail; these are confirmed by a comparison between monaural and binaural time‐threshold measurements.