A major thrhust in this floor project is the collection of low-frequency impact information, below 100 Hz, using special impactors: a tire-dropping machine, two experimental rubber balls supplied by H. Tachibana, and a walker. The frequency range for the standard ISO tapping machine is also extended at 50 Hz. A preliminary analysis of the data collected so far in the project will be presented. Factors that were expected to change the shape of the impact spectrum drastically at low frequencies, so far, have had little or no effect. Changing joist depths from 185 to 285 mm had negligible effect on low-frequency transmission. Changing I-beam depth from 235 to 460 mm did have a significant effect. The best wood joist floor tested to date is still worse than a 150-mm concrete slab. So far in the project, the most effective remedy for excessive low-frequency impact sound is mass.