The Placebo Method, A Comparison of In-Situ Subjective Evaluation Methods for Vehicles

摘要

The "placebo" subjective evaluation method is investigated for sighted in-situ testing of vehicle sound systems. The placebo method is designed to reduce or eliminate bias effects that may occur with typical sighted in-siut subjective evaluations. With the placebo method, some modified program selections are added to the normal program sets that the listeners are to evaluate. Program selections are added to the normal program sets that the listeners are to evaluate. Program modifications can be made to one or more spectral, spatial, dynamic, or temporal parameters. The listeners are instructed that the modified programs are randomly distributed in their program list, and the vehicle's sound system, the modified programs, or both could effect the judgements they make. Hypothetically, this should cause the listeners to focus on judging each individual program selection instead of the vehicle. The placebo method is compared statistically against blind and sighted in-situ methods and the results are given.