In the current studied literature there is a lack of data and documentation on how outside factors affect the performance of ANC headphones. The purpose of this thesis is to investigate how these factors affect ANC headphone performance. The investigation into these factors was done by gathering quantitative data with experiments. The analysis method chosen was an ANOVA-inspired method that compared the differences found in the processed data. The results show that the sample variation between the number of speakers used did not differ by much. However, the variability in the samples collected using different noise types was noticeably higher while short noise resulted in odd-shaped graphs. When combining parameters from the different tests, effects such as graph shapes, seem to remain. These are the conclusions made. When testing with pink noise, the amount of speakers used and how long the pink noise is played makes a minimal difference for attenuation and variation. However, having more speakers and playing the sound for longer durations creates slightly more stable measurements. Unstable noise recordings are unsuitable for product quality testing due to the unreliable results they give. These noise recordings are still suitable for other research purposes.