Here is another article that ETS admits that a high noise level affects the test performance. In my opinion, it is a common sense that quiet environment should be a standard requirement for every test.
Influence of Irrelevant Speech on Standardized Test Perform
Influence of Irrelevant Speech on Standardized Test Performance
"Attempts to reduce distraction to an acceptable level were largely unsuccessful. The impact on actual test performance, however, was slight in the GMAT sample and negligible in both GRE and TOEFL samples.
The conclusion was that intermingling examinees with others who are taking a speaking test remains a concern, primarly because of strong negative perceptions by test takesr. More effective means need to be devised to reduce or control distraction."