Reduction of Mimic Sound in Outside Mirrors Using Jury Test

The so called “mimic” noise centered around a certain frequency from a folding-type outside mirror in vehicles originates from the folding gap of the mirror and is subject to complaints by acoustically sensitive customers. The noise usually is concentrated around a certain frequency above 2 kHz and is heard intermittently depending on the direction of the wind. The noise is thus difficult to identify using general analysis methods using ensemble averages. The sound, however, is clearly identifiable by human ears. Jury testing is performed by recording sound samples inside of vehicles and designing the experiment. Analysis of the test result reveals that the maintenance of gap uniformity as well as the filling of the cavity within the gap is crucial to the noise reduction.