Web browsers have almost since birth sought to host and run feature-rich, compute-intensive and complex applications, within their execution environments (EEs), thereby achieving performance akin to native desktop applications. Studies that have proposed performance improvements to these Web browser EEs together with their respective benchmarks have endeavoured to use proven methodologies with which they confirmed the scientific rigour of those benchmarks, but have often overlooked operating system (OS) noise and the negative impact that it has on benchmarks. This paper identifies the various types of OS noise that exist within a typical Intel-based computer system that utilises a Linux-based OS. While also reviewing what related studies have done to mitigate against them. A series of mitigations were then proposed for the Linux-based system that was then benchmarked using the PolyBench/C benchmarking suite. Whilst not all OS noise was mitigated against, our results confirm that the OS noise mitigations that were provided, significantly reduced OS noise. Further significance of this study is that a more controlled benchmarking environment is made available, due to focusing the CPU processing almost entirely on the benchmarks only, while also enhancing the precision and accuracy of the benchmarks. In this study, we lay down a foundation that will make future Web browser EE as well as any other type of computer software benchmarking more precise and accurate, thereby improving the scientific rigour of those benchmarks.