In a laboratory study on the effects of noise on cognitive performance and wellbeing, a standardised concentrationperformance test (KLT-R) was applied as one of two cognitive tasks. The KLT-R consists of small arithmetic problems. Solving the problems requires concentration as well as memorization of instruction and interim results.

The study was carried out in a repeated measurement design, with an interval of around one week between T1 and T2. Each participant (N=68) worked on the test once under a silent condition and once under a condition with one of three pre-recorded experimental sounds (open-plan office, checkout at fashion retailer, construction site).

In total, results showed on average a significant increase of correctly finished items between T1 and T2, but only a small difference between the silent and the sound condition. However, the amount of this increase (T1, T2) varied with the presentation order of the acoustical conditions and slightly between the three groups with different experimental sounds.

Although a small degree of influence of noise was observed, critical issues arose whether this performance test is appropriate for studies with a repeated measurement design, especially with a very ambitious group of participants, who apparently found ways to optimise their performance between both measurement points.