Extreme sound reduction
When it comes to reducing noise, it is important to look at 2 main criteria. The first is the STC (Sound transmission coefficient) which is the amount of noise reduction that helps stop the noise from passing on from another room, building or neighbour. The second criteria are NRC (Noise reverberation coefficient) which is the amount of noise reduction from within a room, building, echo or absorbing noise.
The next consideration after these two factors have been taken into account is the Pitch or Frequency. Low-pitched noises such as thuds or truck exhaust brakes are difficult to control, it needs thick dense matter in order to reduce the amount of sound. High Pitch noise is reduced with screens etc. Human voices, music (except drumming), car noise, machine cutting noise, healthcare trolley and electronic beeps.