The report presents an overview of the acoustic problems related to light-weight timber floors as they are typically found in modern buildings in the Nordic countries. After a review of recently published literature on the topic, a number of current projects in the Nordic countries are presented. 17 examples of current timber floor constructions are described and measuring results are given as well as subjective judgements of the acoustic quality.The relation between annoyance and impact sound level is analysed on the basis of a number of field investigations found in the literature. It is concluded that the frequency range for measurements should be extended below 100 Hz, at least down to 50 Hz and preferably down to 20 Hz. It is found that deflection and vibration of the floor are often evaluated as a problem in timber floor constructions.