Impact level

Professional Definition

Impact sound level (Ln) is the level of sound pressure measured in the receiving room when a standardized reference tapping machine is operating in the room above (the source room).

In contrast to airborne sound insulation (where the higher the score, the better), here the lower the impact sound level, the better the insulation. This means that less noise has penetrated through the ceiling to the room below. Measurements are taken using a machine with hammers that generates a standard mechanical excitation on the ceiling.

Acoustics in Simple Words

Imagine the difference between shouting at a wall and hitting it with a hammer. Shouting is airborne sound – it reflects off the wall. Hitting the wall with a hammer causes it to vibrate, sending vibrations throughout the structure like electricity through a wire. Impact sound level tells us how loud it will be in the room below when someone is "hammering" on the floor above. If the floor is hard (e.g. tiles without insulation), the sound will travel perfectly. If we lay a thick carpet or a special mat (floating floor) there, the vibrations will be dampened at the source.

Summary

Impact sound level is a critical parameter in multi-family construction, determining the comfort of residents. Its reduction requires the use of construction solutions, such as floating floors, as simply thickening the ceiling rarely yields satisfactory results.