Soundproofing against neighbour noise: up to 60 dBA for €100/m2

Soundproofing against neighbour noise costs €100/m2 and doesn't always bring silence

The technical solution exists, it is quantified and it has a price. Soundproofing a home against airborne noise from the neighbour below —voices, television, music— can achieve overall insulation of up to 60 dBA if built as a box within a box, according to a calculation circulating in the debate. In other words: a person shouting at 90-95 dBA would no longer be heard. The problem is not the physics, it's the bill and the building's skeleton.

The figures used in the industry are specific: around 100 euros per square metre for the ceiling and 80 per square metre for walls and floors, with acoustic wooden doors that can exceed 900 euros per unit. For a 28 m2 living room and a 14 m2 bedroom, the investment soars above 6,000 euros in materials and specialised labour alone.

Which material actually works and which is a waste of money

The technical consensus dismantles much of the folklore. Egg-crate rubber panels, the typical anechoic foam cones and thin sheets of foam rubber are useful for acoustic treatment —conditioning a rehearsal room— but not for soundproofing. Absorbing sound inside a room and blocking it from outside are different problems. A layer of rock wool can absorb 99% of acoustic energy, but that only equals 20 dB of insulation. A solid concrete wall, on the other hand, exceeds 60 dB.

The system recommended by experts combines a self-supporting plasterboard structure, 40 kg/m3 rock wool, heavy 5 kg/m2 EPDM sheets and a decoupled installation with elastic springs or anti-vibration mounts. Lead sheeting of 1-2 mm appears in several interventions as the most effective insulation per unit of thickness, with the drawback of its weight and price. Asphalt fabric of the Danosa type is the usual resource in car audio, although its use in homes is not documented.

Impact noise is another battle entirely

Here comes the bad news. Impact noises —heels, dragged furniture, sharp knocks— travel through the building's structure: floor slabs, columns and beams. Insulating your own floor reduces part of the problem, but the columns keep transmitting vibration. The most repeated recommendation is to tackle the source: a simple rug at the neighbour's home prevents more noise than any works done from below. Being on the top floor helps, but it doesn't eliminate structural transmission.

How the problem evolves once the noise is already inside

The conversation drifts towards specific cases: a chest freezer against the party wall emitting low-frequency noise at night, roller shutter boxes filtering traffic from a street with two lanes each way and buses, or a pub installed below a bedroom that ended up with excellent insulation after running acoustic tests during the works. The pattern repeats itself: when the source cooperates, the result is good; when it doesn't, the tenant ends up with 80-euro custom earplugs which, according to several accounts, muffle no more than the 15-euro foam ones.

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The prediction with reservations: as long as regulations fail to penalise neighbour noise as harshly as other abusa, the burden will keep falling on whoever wants to sleep. And that person, today, pays for the works, the silence and the bill.