If you experiment with listening to the sound of each number it gets easier to understand Albert each time. When you are practicing, I recommend that you do so on the earlier notebooks. To get rid the ambiance you can turn off and on your monitor (not the computer as a whole like putting it to sleep, just the screen), doing this really helps you hear each detail of the pronunciation of each number. Keep in mind that the game keeps running while the screen is off.
Also, the difference between 1 and 5 is that 5 sounds and has more of an "ah-i" sound while 1 sounds like the word "on". 5 also has a very slight vibrato at the start of the word with an "f" sound as in four.