Click here to purchase the entire book in PDF format. Hedonic tests Typically, when people who don't do listening tests (or perceptual tests in general) for a living talk about listening tests, they mean a hedonic listening test. What they're usually interested in is which product people prefer - because they're interested in selling more of something. So, in a hedonic test, you're trying to find out what people like, or what they prefer. If I put a Burger King Whopper and a McDonald's Big Mac in front of you, which one would you prefer to eat (assuming that you are able to eat at least one of them...)? A second question after ``which one do you prefer'' is ``how much more do you you like it?'' This allows the greedy bean counters to set pricing levels. If you like a Whopper two times as much as a Big Mac, then you'll pay two times more for it. This makes the accountants at Burger King happy. Unfortunately, doing a hedonic test is not easy. Let's say that you're comparing two brands of loudspeakers. Your subjects must not, under any circumstances, know what they're listening to - they can't know the brands of the speakers, they shouldn't even be able to see empty speaker boxes on the way into the listening room. This will distort their response. In other words, it absolutely must be a blind test - where the subject knows nothing about what it is that you're testing, they can't even be allowed to think they know what you're testing. Also, you have to make sure that, apart from the independent variable, all other aspects of the comparison are equal. For example, if you were testing preference for amount of sugar in coffee by giving people coffee cup ``A'' with 1 teaspoon of sugar compared to cup ``B'' with no sugar, you have to make sure that the coffee in both cups is the same brand of coffee, they're both the same temperature, the two mugs look and feel identical etc. etc... If there are any differences other than the independent variable(s) then you will never know what you tested. If you're testing loudspeakers, you have to ensure that both pairs of speakers play at the same output level, and that they're in exactly the same location in the room, otherwise, you might be comparing the subject's preference for loudness, or room placement, for example. The danger with hedonic testing is that the results are almost always multidimensional. This means that your decision as to whether you prefer or like something is dependent on more than one thing. For example, if we do a ``how much do your like it'' test for loudspeakers, your answers will be dependent on the music that's used in the test. If you hate the music, you might like the speakers less. If your boyfriend broke up with you or your dog died the day before the test, you might like the speakers less (unless you hated your boyfriend and your dog, in which case, your might like the speakers more...). Think of the implications of doing a taste test on beer using a subject with a hangover - you probably won't be able to trust the results of that test... Everyone who does the test will have a different opinion about how much they like what's being tested, and you may not be able to figure out what attribute of the things being tested contribute to the person liking something or not, because it's possible that the reason they like it or not might have nothing to do with anything you know about what's being tested. Of course, you also have to consider that different people have different preferences. I like coffee with cream and sugar. Other people prefer it black. For this reason, you have to use a very large group of subjects when you do a hedonic test. It's not unusual to require something on the order of hundreds of people doing the test until you can get some reliable data that indicates what the general population will think about what you're testing.