To have an idea of what to expect, will this block someone in the next room with thin walls from hearing conversations in an office env?

For that to happen is quite costly and would require construction! You see sound moves in a wave, like water! Wherever there is space, sound will go there to get out! So....think the air vents, door frames, windows, and air gaps in the celular structure of the wall! Not only that though, sound vibrates things, and those things then re-produce that sound through vibration as well! So to kill sound you need mass! First thing you do is grab some MLV-mass loaded vinyl and cover your wall that you don't want people listening to you through! Then after doing that cover the MLV on the wall with another layer of drywall! If you can leave a 1" airgap between the MLV and the new layer of drywall! Then do the same to the ceiling! Then get special air-vents, and seal them from sound! Then on the walls put these all over the wall's on the entire room! Not on every single square inch of space, just around the room from crotch to head height! And that should work! Oh and get a door that's super thick and made of real wood, and not hallow! The heavier the better, the thicker the better, the more mass the better! The more mass you have the more soundproof it is!

can this be effective in blocking generator noise? what dBL reduction can be expected? building a generator box

Absolutely do not buy this for that, just pick up the heavy grade sound absorb material, just literally type in "sound absorbing material" in search box above and you will get a load of choices. http://www.amazon.com/s/ref=nb_sb_ss_i_3_12?url=search-alias%3Daps&field-keywords=sound+absorbing+material&sprefix=sound+absorbing+material%2Caps%2C151

How many panels come in this order.. Is it 4 like reflected on the picture or is it only one panel?

You get only 1 panel. They are just showing you the different colors they come in. The panels are somewhat expensive but I feel they are well worth it. They are also easy to hang on the wall.

I am trying to reduce sound and echo in a cafeteria area. The dimensions are approximately 40x80 feet. How many of these tiles do you think I need?

These panels appear to be quite effective in the small home recording studio I have. For a large area, some might argue the simple answer is the more the better. I think the main aim in your situation is to significantly cut the way sound waves bounce around a room, rather than achieving a more complete sound absorption desirable in a recording studio. I would aim to place the panels vertically about midway up each wall, leaving a space of perhaps no more than six feet between each. It's important to ensure that panels on opposing walls are not directly opposite each other. That way, a blank space on one wall should have a panel directly opposite it on the wall facing it, and visa versa. You are aiming to minimise sound waves bouncing between two hard surfaces. So, for example. you might have 10 panels on each long wall, staggered so as not to face each other, and maybe five or six on each shorter wall, again staggered so as to face a blank wall space on the opposite wall. If you have the budget and the room height, suspending some panels from the ceiling with a few inches gap between them and the ceiling should add considerably to the effect. Hope that helps

Manufacturer	ATS Acoustics
UPC	689466275049
Item Weight	3.74 Kilograms
Product Dimensions	121.92 x 60.96 x 0.25 cm; 3.74 kg
Item model number	B
Material Type	Wool

Ats Acoustic Panel 24X48X2 Inches In Black

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