If we hear of audio problems in classrooms, low volume while watching online content such as Youtube videos, check the following.
Right Click on the Speaker/sound icon in the system tray (bottom right). Select Playback Devices.
Double Click on the Speaker item.
Go to the Levels tab. Click the Balance on the top item usually labeled Output.
Make sure both sliders are pushed to the right for 100% volume.
Next, Click Enhancements (may or may not appear depending on sound system).
If present, enable sound effects mode Loudness Equalization. This should increase volume by roughly 25%.
Another thing that can be done is to enable the equalizer. then on the Settings below, click the ... and increase the middle 4 sliders to improve the mid-tones.