Tuffatuffa AC noise has different frequencies. One of them being Humm, which typically transfers mechanically (making adjacent structures vibrate with them). Wood is typically used in combination with space, creating sound "traps" for lower frequencies (the humming part of your AC noise). Remember, higher frequencies have shorter wave lengths, so combining different density materials is what you're going for, unless there's a specific frequency range you want to address. This seems like a good link. Let me know if it doesn't answer your questions and I'll do some more research Bass trap I think you're looking for acoustic insulation that wont look bad. Since AC noise will have a variation of frequencies, the more diverse materials you use, the more diverse the frequencies you will absorb. Then, the higher frequencies will just be reflected by the solid surface of the tufa. So, this is how I would do it: 1) Make your wall with a frame of 2x4s for shape 2) Take a piece of plywood or something to go along the interior. Staple it 2 inches from the border (so you're in the middle of the wall). 3) Fill the remaining space (which should be about 2 inches on each side) with foam, carpet or whatever you can find and dispose of. 4) Use some kind of metal lathe to give the tufa something to cling to, and stable it to your wooden frame. 5) If you want to take it a step further, before covering with tuva, cut a few sections of PVC pipe and place it at even intervals accross the side of your wall (about an inch or two of separation). This will insure different frequencies are reflected in different directions 6) Cover the whole thing with tufa. Then, cover with plastic so you can isolate the foam from your wet tufa when you apply Now you have an effective bass(humm) trap, and high and mid frequency absorbtion and reflection (with the interior foam for absorbtion and the corrugated tufa surface for reflection) If you can, lie your "wall" on the floor when applying the tufa. Or at least at an angle so our tufa doesn't slide down. You'll find this is where the lathe will come in handy ;-) Forget my comment about replacing the AC. I have a noisy AC myself, so I am biased towards just dumping the thing :-) OK, I'm typing a lot and I don't know if I'm answering your questions. Let me know if there's anything else I can do to help.

Thanks, Billie I didn't cover it for the first night. I didn't want the piece to get the same texture as the bag. The next morning I covered it up first thing. As for the bird baths and the like, when knocking on them, I think the peat moss gives them a more muffled sound. This is why I thought it wasn't made of concrete (straight mortar). I'm feeling pretty confident about what my next piece will be. As for the manhandling, my next piece will require me to flip it over at some point, before it's too late to carve. So far, both of my molds have been outter molds. I've noticed that the rim, which is up against the plastic, which in turn is up against the floor, always has a plastic glue-like finish. I want to make sure I can manipulate this before the tufa is dry, and that will require flipping over. Also, I am going for a rock-like look, which means thicker walls, which means heavier piece, which means, handling it will require precise timing. You'd think I'm crazy going for something more difficult when this simple thing failed, but I think I learned some valuable lessons here. I'm going to start creating the mold. One of the lessons I learned, is you can make a mold out of anything. This new approach is going to be really interesting and I am surely going to post it here, hopefully with successful results this time :-) As for working outside, now is a good time here in FL, because it's not raining, although I did have a stroke of bad luck the next day, because it did rain. Luckily, my tufa had been covered by then ;-)

No, I don't, I just posted about concrete work I need done. I told one guy if I could have exactly what I wanted, I'd have it all ripped out and faced with brick like you want to do, sidewalks and all, except the public sidewalk. I just saw a photo somewhere and it looked fantastic. It would have to be done right or it isn't going to work, and you will have to keep the steps in proper proportion and not so high (adding bricks will make them higher). Maybe it would be better to repour all the steps and have them right, but the stoops would be a problem. I have them, too, and if it hadn't been for the odd configuration of porch roof, gutters, and added expense, etc., I'd have ripped that all out and put a deck type front (not wood but poured slab) on it with quality wood or iron (not from the big box stores) railing and bannisters. I saw one in a magazine and kept the photo for years.

Would suggest filling crack w/ ridged foam board before using the calking material of choice. The calk goo will just ooze to the bottom of the void (w/o this or a similar step) and result in a big drippy mess as well as a waste of your $$.