redstone signal weakener

There can be a block that weakens the signal strength of a redstone on it by 2 instead of 1 per block. Say this block is glass, then when redstone block is paced on top of a floor of glass, the redstone signal will diminish after 7 redstone dust placed on this floor. Another alternative could be comparator-like block that will dampen the redstone signal. Even though comparator can do it in subtraction mode, it is not 1-wide.