Are you planning a practice? Here you can find out everything you need to know about the necessary decibel levels (dB), the SIA 181 standard and why ventilation is often your biggest sound bridge.
For doctors, therapists and solicitors, the standard sound insulation in modern offices is often insufficient. To maintain confidentiality, insulation values of at least 50–55 dB are required. The biggest weak points are usually not the walls themselves, but doors without floor seals and continuous ventilation ducts. Anyone planning a practice must comply with the SIA 181 standard.
Imagine a patient sitting in your waiting room. He is leafing through a magazine, and it is quiet. Suddenly, he hears voices coming from the treatment room next door. He cannot understand every word, but he can hear that the patient is upset.
At that moment, the relationship of trust is damaged – not only with the patient in the room, but also with the one waiting outside. He now knows: ‘You can hear everything here. Even about me.’
This is a classic problem for tenants of practice premises: many commercial spaces are let as ‘standard office space’. But what is perfectly acceptable for a marketing team or an accounting department (you can hear your colleagues laughing) is an absolute no-go for a psychotherapy or doctor's practice.
Before we get to the solutions, we need to distinguish between two terms that are often confused:
Room acoustics: How does sound reverberate in the room? (Solution: carpets, acoustic panels).
Building acoustics (sound insulation): How much noise penetrates through the wall to the outside?
Building acoustics are almost exclusively decisive for your discretion. And here in Switzerland, the hard figures of the SIA 181 standard reign supreme.
Sound insulation is measured in decibels (dB). The value $R'_w$ indicates how much sound the wall ‘absorbs’. The higher the better. Here is a realistic assessment for everyday practice:
35–40 dB (standard drywall, single planking): This is the standard in many inexpensive office fittings. Normal conversations can be heard in the next room. Unsuitable for a practice.
40–45 dB (office partition, insulated): Conversations can be heard as murmurs, loud words are understandable. Still risky for confidential therapy sessions.
50–55 dB (increased sound insulation): Normal conversations are inaudible. Loud arguments or shouting are only faintly perceptible, but the content cannot be understood. This is your target value.
You can have the best walls built – but if you ignore the following three sound bridges, the investment will have been in vain. Sound behaves like water: it seeks out the smallest hole.
1. The doors (the eye of the needle)
A solid wall is useless if it is next to a hollow honeycomb door from the DIY store. Practice doors require a high sound insulation class (at least 37 dB, preferably 42 dB). The killer: the air gap under the door. Without a drop seal (Schallex) that automatically presses against the floor when the door is closed, the sound simply creeps through underneath.
2. The suspended ceiling (the high flyer)
In many offices, the partition walls only go up to the suspended grid ceiling (Odenwald ceiling), but not to the ‘real’ concrete ceiling above. The cavity above the ceiling panels is often open. The sound simply climbs over the wall and falls back down into the neighbouring room (longitudinal sound insulation). Solution: The plasterboard walls must be raised to the raw ceiling and sealed there. Alternatively, ‘sound baffles’ must be installed in the ceiling cavity.
3. Ventilation and cable ducts (the telephone)
Does a shared ventilation duct connect two treatment rooms? Without a silencer in the pipe, the ventilation acts like a telephone. If you speak into the outlet in room A, the sound comes through crystal clear in room B. Continuous parapet ducts for sockets are also popular sound transmitters.
When viewing a space or planning tenant improvements, pay attention to these points:
Wall construction: Ask about double panelling. Two layers of plasterboard (2x 12.5 mm) on each side of the stud frame provide significantly more soundproofing and mass than a single layer.
Floor plan: Do not place sensitive rooms (therapy) directly next to the waiting room. Use buffer zones such as the archive, the laboratory or a corridor in between.
Sound masking: A modern solution when structural changes are no longer possible. Special loudspeakers in the waiting room generate a barely perceptible background noise (white noise) that overlays speech frequencies and makes conversations from the treatment room incomprehensible.
Soundproofing is not a luxury, but the basis of your professional existence as a doctor or therapist. Do not rely on statements such as ‘This is a quiet building’. Insist on specific dB values in accordance with SIA 181 for the partition walls and doors of your treatment rooms in the rental agreement or building specifications. It is significantly cheaper to invest an additional CHF 5'000 in drywall and doors when moving in than to have to close your practice for renovation later due to complaints.
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