Manufacturers love sound-insulation figures, but few explain what they actually mean in practice. Let us break it down.
The decibel scale is non-linear
A 10 dB reduction is perceived by the human ear as roughly twice as quiet. So the difference between 25 dB (Lite) and 35 dB (Premium) is not “a little better” — it is a substantially different level of privacy.
- A normal office conversation: ~65 dB
- A Premium booth cuts 35 dB → you hear ~30 dB from the inside
- 30 dB is the level of a quiet whisper or a library
What ISO 11957 is
It is the international standard for measuring the sound insulation of booths. When a manufacturer states “35 dB to ISO 11957”, it means the insulation was measured in an independent laboratory following a defined method — not a marketing figure someone made up.
Why insulation is asymmetric
The five-layer Silentbox wall dampens high frequencies more strongly than low ones. This is no accident: it is precisely in the high-frequency range that speech intelligibility lies. So even if a low hum passes through slightly, the words cannot be made out — and that is exactly what confidentiality is.
−35 dB is the threshold beyond which a confidential conversation stays confidential. That is why the Premium series is chosen by banks, law firms and audit companies.
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