If you are taking the TOEFL Home Edition, make sure to check your microphone. Don’t just use the ProctorU website test, but actually make a recording and listen to it.
I often get sample answers from students that sound horrible. They sound like they were recorded using Thomas Edison’s wax tube machine. I can barely understand what they are saying. The worst part is that the TOEFL raters will have the same challenge! G-d only knows how this problem will affect the automated scoring engine used by ETS nowadays.
Internal microphones (like in your laptop) are often terrible. If yours is bad, consider getting an external microphone to use on the test. Just remember that you cannot use headphones. You should use one that sits on your desk.
I’m not a microphone expert, but my favorite cheap and tiny model is this one, from Samson.