soz to post about a minor point, but i hope everyone learns!!!!!
when you upload a video onto the internet,
take the audio file for the video,
and load it into an audio editor.
look at the waveform. if it's very small, people using laptops cannot hear. open the effects/process menu on your wave editor, and amplify it/adjust gain/normalise/compress it until the waveform takes up most of the available range.
any of those processes will work, you only need to use one, whichever is easiest. always, the trick is to limit the peaks and bring up the average level, so a compressor or limiter with make-up gain are good choices, but it's better even to just amplify it and clip the peaks off, which may sound distorted, than be too quiet.
it's easy to do and it makes all the difference between whether your video has sound for the audience or not