Soundproof doors help to reduce or prevent nuisance caused by sound transmission from neighbouring rooms.
However, due to the standardised minimum requirements for sound insulation, it cannot be expected that noises of any kind will be completely imperceptible.
Insulating does not mean "hearing nothing"
Soundproof doors insulate the noise level by a certain amount. This level is determined in accordance with standardised boundary and measurement conditions. Sound insulation values of 27, 32, 37 or 42 dB(A) are common. While humans hear frequencies between 16 Hz and 16000 Hz, building acoustics measure between (50) 100-5000 Hz.
The sound level (dB) is a logarithmic quantity. A change of 1 dB cannot be detected by humans, +3 dB is perceived as noticeably louder, +5 dB as significantly louder and a difference of 10 dB is equivalent to halving or doubling the volume.
Many soundproof doors are specified with a sound insulation class (SSK). SSK1 would be 27 dB, SSK2 corresponds to 32 dB and SSK 3 stands for 37 dB - these are the values for installed, ready-to-operate doors. The laboratory values are always 5 dB higher.
With every increase in the sound insulation requirement (dB = logarithmic value), the effort required to realise this increase increases. For this reason, doors above 42 dB (laboratory value) are not the rule. Single-shell constructions can still be realised for doors up to 47 dB. Up to 52 dB, double-shell constructions are usually used. Above 52 dB, double doors are usually used.
The crux of installation and maintenance
It goes without saying that soundproof doors only work when closed. As the correct adjustment of the doors is important, the manufacturer's specifications should be regarded as binding. As a rule, the lowerable floor seals may only be shortened to the frame rebate dimension (i.e. the rubber seal protrudes from the bottom of the door leaf).
TPO installs automatic floor seals from Athmer, Planet and Deventer.
As with all functional doors, it is important to maintain the doors so that their function is guaranteed in the long term.
Sound insulation is more than just a question of comfort. The sound insulation values of doors are specified in DIN 4109 and are therefore binding.
You can find basic information on the subject of sound insulation here: Soundproofing_Introduction
