You need to boost the volume of the songs or videos that been played on your Mac Os X if its too low to hear. Here are the simple instructions on how to boost the volume level of songs during playback in iTunes.

1. Make sure that you are in iTunes.

2. From the library select a song and then press Command+ i on the keyboard. You can also select the item and right click on it, then select Get Info.

3. Now you have info tab opened for you and you have to open Options tab.

4. Move the volume slider to make it 100% and click on OK.