This test aims at evaluating the perceived quality of a voice timbre transformation to produce a mouth opening/closing effect.
Some of the sounds that you will hear are original unprocessed recordings of various sustained vowels from 2 singers.
Those original sounds have also been transformed in order to apply the desired timbre effect. This test aims at evaluating the quality of those transformations.
Those original and transformed sounds are presented to you in a random order.

You are asked to evaluate and score each sound on a 1 to 5 scale, where numbers correspond to the following labels:

Rating	Label
5	Excellent
4	Good
3	Fair
2	Poor
1	Bad

A score of 1 thus corresponds to a highly degraded sound with very audible artifacts and/or an unnatural timbre, and a score of 5 corresponds to a perfectly natural-sounding sound, for which no processing of any kind is perceived, as it should be the case for original recordings.

There is no "correct" answer. It is only about your subjective preference.