Accumulating evidence suggests that ultrasound visual feedback increases the treatment efficacy for persistent speech sound errors. However, the available evidence is mostly from English. This is a feasibility study of ultrasound visual feedback for treating distortion of Finnish [r]. We developed a web-based application for auditory-perceptual judgement. We investigated the impact of listener's experience on perceptual judgement and the intra-rater reliability of listeners. Four boys (10-11 years) with distortion of [r], otherwise typical development, partook in eight ultrasound treatment sessions. In total, 117 [r] samples collected at pre- and post-intervention were judged with visual analogue scale (VAS) by two listener groups: five speech and language therapists (SLTs) and six SLT students. We constructed a linear mixed-effects model with fixed effects for time and listener group and several random effects. Our findings indicate that measurement time had a significant main effect on judgement results, chi(2) = 78.82, p < 0.001. Effect of listener group was non-significant, but a significant main effect of interaction of group x time, chi(2) = 6.33, p < 0.012 was observed. We further explored the effect of group with nested models, and results revealed a non-significant effect of group. The average intra-rater correlation of the 11 listeners was 0.83 for the pre-intervention samples and 0.92 for post-intervention showing a good or excellent degree of agreement. Finnish [r] sound can be evaluated with VAS and ultrasound visual feedback is a feasible and promising method in treatment for distortion of [r], and its efficacy should be further assessed.