The Acoustics of Floors in Condominiums

35 causes the floor to deflect like a trampoline as he pads along. Floor squeak sounds like a birdcall, which produces noise by metal rubbing on wood. Most floor-ceiling noise problems fall into one or more of these categories although occasionally there are structurally transmitted sounds due to equipment, doors or drawers closing, or furniture sliding along the floor. Airborne noise Airborne noise is created in one space and is transmitted through the air and through an intervening partition into the adjacent space. Sources might include TV, stereo systems, or simple conversation. The isolation of airborne noise such as speech is well characterized by the Sound Transmission Class (STC) rating. The STC rating is the result of a test performed in accordance with ASTM E 90 or ISO 140 laboratory test standards. To do the test a partition is built into a heavy wall separating two concrete test chambers in a laboratory. A standard sound is created in one room, called the source room, and transmitted through the partition and into the receiver room. The difference between the levels in the source and receiver room, adjusted for the area of the partition and the absorption in the receiver room is the transmission loss in decibels. The measured transmission loss values in 16 third-octave frequency bands are compared to a standard curve (ASTM E413) to determine the STC rating. The higher the STC rating, the better the partition is at stopping airborne noise. Under field (F) conditions the measured FSTC rating is about five points lower than the laboratory rating, and this difference is acknowledged in the building codes. Thus if an STC 50 is the required laboratory rating, a field test of 45 is equivalent. In California the test procedure has been diluted by eliminating the inclusion of the correction for the absorption in the receiving room Reasonable expectation of the buyer In selecting the appropriate design criterion for a given level of quality, the designer should consider the type of building and the level of quality expected by the buyer. As the perceived quality of a residence increases, so too do the expectations for a quiet environment. This expectation of quality may be based on cost, location, sales information provided to the buyer, or because a person is purchasing a permanent home rather than renting an apartment. Unfortunately, too often builders put money into the appearance of a residential …