Right, I wasn't thinking about it this way, and I probably wouldn't for the purpose of blocking EM. In principle, low frequency penetrates better but as you say

Right, I wasn't thinking about it this way, and I probably wouldn't for the purpose of blocking EM. In principle, low frequency penetrates better but as you say high frequency can get into things more (but doesn't necessarily). Of course I didn't actually look up what frequencies we're talking about- low and high can mean a lot of different things