You probably have faced the situation of not being happy with the recording you have for your Powerpoint presentation. It is not very easy to find a way out of that.
Basically, Powerpoint creates an icon and gives you the opportunity to give a name to the recording for each slide, so that you can use that resource a bit better than you currently do: Name all recordings in a unique way. Then use the search button from MS (the rectangle that is found to the side of the MS button) to find the file. Click on open file location after right clicking over the name, which will appear at the top of the rectangle that is built over the MS button after you press enter on the search bar.
You then convert the file, if necessary, or you record the message using the Voice Recorder from your computer. You can even use iTunes to rename the extension of the file, as we have explained here earlier on (will give you a .wav). You then drag the file to inside of Audacity and perform at least these actions: Leveling, Noise Reduction, Equalizer, and Normalizer. This sequence, per se, will give you a much better quality of sound. You then must export the file to be able to insert it in your Powerpoint presentation. You will use the resource Insert Audio in this case.