I'm listening BBC in 4-speed

I wrote I listened BBC twice speed maybe.

After 2-speed, I'm be able to listen to BBC 1-speed yesterday.
I thought it's interesting that.

So I'm listening 4-speed of BBC. I don't understand in 4-speed. But 2 days ago, I can't understand 2-speed, and now 3-speed a little. So someday I can understand in 4-speed, and I improve listening skill more.