Buying the sound of silence in your condo Some home buyers have discovered a problem with their luxury condos: noise. It's not noise from the outside, like traffic, it's from people living above and below them in the building. The qualities buyers look for in a home, huge windows, an open floor plan and central location, can translate into disruptive noise after they move in. After some months of talks with the neighbors, one couple hired Manhattan-based City Soundproofing to replace the ceilings for a cost of about $30,000. "People spend a lot of money on an apartment. When they get home, they don't want to hear their neighbors' techno music," said Benjamin Sachwald, director of acoustics at AKRF, a New York engineering firm. Buyers want the floor-to-ceiling windows, open layouts, and proximity to public transportation. But add to that noise from heating and cooling, elevators, spa filters, wine-cellar compressors and you have a lot of noise. Developers are pouring money into new buildings to combat the problem. In Florida one developer is pitching condos as having an acoustical rating above local requirements. Another luxury builder has flooring consisting of a 10-inch concrete slab topped by a rubber mat.