Due to the fact that psychophysical scaling is relative to<br>context, where stimuli are contrasted with those immediately<br>preceding, we decided to collect intensity and hedonic<br>ratings subsequent to the measurement of odor frequency.<br>After each single measurement of 10 minutes’ duration the<br>panelist had to evaluate Wrst intensity and then hedonic tone<br>on the second page of the data record form (see Fig. 2).<br>When making this decision only the positive records of the<br>source-speciWc odor and not all of the 60 samples were considered.<br>To assess odor intensity a six-point scale with values<br>from “1—very weak”, “2—weak”, “3—distinct”, “4—<br>strong”, “5—very strong” to “6—extremely strong”<br>(Guideline VDI 3882 Part 1 1992, page 9) was used. The<br>panelists were advised to use their own response time as a<br>hint and give this score at a point where the odor quality is<br>immediately identiWable and clearly evident. Having only<br>those records with source speciWc odors in mind, the panelist<br>evaluated how strong the strongest odor impression<br>was, how often it occurred (5—point scale from “1—<br>rarely” to “5—always”) and then he estimated the average<br>odor impression (6—point intensity scale). In assessing<br>hedonic tone a nine-point scale with values ranging from<br>“¡4—extremely unpleasant” through “0—neither pleas-
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