Binary informational video

In class today we watched a guy talking about the binary code. One new thing I learned was instead of using ten digits to count the binary system uses two digits "1" and "0". A second new thing I learned was analog signal in electronics and when sound has a high pitch it has a high voltage while a sound with a low pitch will have low voltage. A third new thing I learned was digital signal in electronics and how it can be balanced out in digits for the right sound output. One thing I don't understand well is the big picture of how sound relates to the binary system. A second thing that I don't understand well is the base numerals. One thing I would like to know more about is what are the differences between the 3 methods (decimal, base four, binary).