Impact sound

Professional Definition

A specific form of impact noise generated by the vibration of the ceiling during its use.

Impact sound is produced as a result of direct mechanical contact between a source and the structure (e.g., the floor). The kinetic energy of the impact excites vibrations in the ceiling slab, which are then radiated as an acoustic wave to the room below. In construction, the parameter that defines sound insulation from this type of noise is weighted normalized impact sound level (L'n,w) – the lower its value, the better the acoustic protection of the ceiling.

Acoustics in Simple Terms

Imagine that the ceiling of your neighbor is a large drum membrane. When your neighbor walks on their floor in hard shoes, they hit this membrane like a drumstick. You, sitting in the room below, are inside the resonating box of this drum. Even if the ceiling is thick and airtight to conversations (airborne noise), a hammering (or heel) directly against the concrete makes the whole structure vibrate and "play," emitting noise into your apartment.

Summary

Impact sound is noise resulting from the mechanical excitation of the ceiling, e.g., from footsteps. Its effective suppression requires the use of floating floors that separate the usable layer from the load-bearing structure of the building.