Click here to purchase the entire book in PDF format. Non-hedonic tests Usually, but not always, non-hedonic tests (where the subject is asked to grade an aspect of the sound and you don't care whether he or she likes or prefers it) are a little easier to design. Again, you must be absolutely certain that, if you're comparing stimuli, the only differences between them are the independent variables. For example, if you're testing perception of image width with a centre speaker vs. a phantom centre, you must ensure that the two stimuli are the same loudness, since loudness might affect the perception of image width. Often, one of the big problems with doing a non-hedonic test is that you have to be absolutely certain that the subject understands the question you're asking them. For example, if you're testing sweetness of coffee, you give the subject 5 cups of coffee, each with a different amount of sugar, and you ask them to rank the cups from least sweet to most sweet. You have to be certain in this test that a subject that knows in advance that they like sweet coffee is not rating them from worst to best. You could ensure that this is the case by having one of the cups being much too sweet, or you could just make sure that your subjects are trained well enough to know how to answer the question they've been asked (and not another question that they've invented in their head...).