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 vehiclesound systems. The placebo method is designed to reduce or eliminate bias eflects that mayoccur with typical sighted in-situ subjective evaluations. With the placebo method, somemodified program selections are added to the normal program sets that the listeners are toevaluate. Program modifications can be made to one or more spectral. spatial, dvnamic, ortemporal parameters. The listeners are instructed that the modified programs are randomlydistributed in their program list, and the vehicle s sound system, the modtjied programs, or bothcould effect thej’udgements they make. Hypothetically, this should cause the listeners to focus onjudging each individual program selection instead of the vehicle. The placebo method iscompared statistically and.finctionally against blind and sighted in-situ methods and the resultsare given.