Abstract
This study considers whether the psychological impression for annoyance of noise during a mental task can be reduced by use of masking effect. More specifically, the authors first discussed how the psychological impression for annoyance of noise and performance indicated by factor such as the percentage of correct answers and reaction time would change under the influence of meaningless noise or interested/uninterested meaningful noise. Next, an investigation was made into how the above items would change when meaningful noise was masked with meaningless noise.