So I like the first one better. It is simpler, will scale well looking good in a small size and captures the idea of Hertz really well. Green gives an idea of up movement, and the looking at it from this angles clearly shows it going up and down. This down angle balances the up of the green. The problem with the second image is the squares don't add value, ie communicate additional information. (I realize it shows a base or foundation for the wave length, but IMO that is not worth it.) Overall, I think this is a good very solid logo. In improvements, there is something about the coloring, I am not quite sure on. Take this with a grain of salt, but I think if there were multiple shades of green this is not the first one I would choose. I would go for a little darker. That said, overall really good job getting a lot into the logo.