Rooms & neighbours

Acoustics and sound insulation before you rent: how to judge noise when viewing a flat

Rooms & neighbours · Published 2026-10-25

Every window on a street front is a path for traffic noise, and every shared wall a path for the neighbours'. Photo: Chris Barbalis, Wikimedia Commons, CC0 1.0.

Noise is one of the few things about a flat that you cannot repaint, rearrange or replace. A cheap rent next to a bus depot, or a bedroom under a neighbour's hard floor, costs sleep every night of the lease. The good news is that most noise problems can be spotted, or at least suspected, during a viewing, if you know where sound comes from and how buildings let it through.

Where the noise in a flat comes from

It helps to sort sound by source and by path, because each calls for a different check.

• Outdoor noise: road traffic, trains, aircraft, bars and restaurants, deliveries, schools and building sites. It comes in mainly through windows, doors and ventilation openings.
• Airborne noise from neighbours: voices, television, music. It travels through separating walls and floors and around their edges.
• Impact noise: footsteps, dropped objects, furniture dragged on a hard floor, doors slamming. It is generated in the structure itself and is usually the most complained-about noise in flats.
• Building services: lifts, pumps, extract fans, plumbing, rubbish chutes, heat pumps and air-conditioning units on the roof or a neighbour's balcony.

Before you sign a lease, compare several flats and the neighbourhoods around them, and note what you hear at each one.

A little acoustics

Sound levels are measured in decibels (dB), a logarithmic scale: a rise of about 10 dB is heard as roughly twice as loud. Building insulation is described the same way, as the number of decibels a wall, floor or window takes off. Three principles explain most of what you will hear in a flat:

1. Mass blocks sound. Heavy, dense walls (brick, block, concrete) insulate better than light ones. In theory, doubling the mass of a single wall improves its insulation by only around 5 to 6 dB, which is why good light walls rely on separate layers instead.
2. Low frequencies get through most easily. A wall that turns a neighbour's voice into a murmur may let the bass of their music and the thud of their footsteps straight through.
3. Gaps and side paths ruin good walls. A keyhole-sized gap, a shared duct or a floor that runs continuously under a wall (so-called flanking paths) can carry more sound than the wall itself.

The street and the neighbourhood

Outdoor noise varies by hour and by day, so one visit tells you little. If you can, return at the times that matter to you: a weekday rush hour, a Friday or Saturday night, and early morning if you sleep lightly.

• Look for traffic lights, junctions, bus stops and speed bumps right outside, where vehicles brake and accelerate.
• Note bars, takeaways with late extraction fans, loading bays and anything that operates at night.
• Check whether the bedroom faces the street or a courtyard. A quiet side for sleeping matters more than a quiet living room.
• Look up official noise maps. EU member states publish strategic noise maps for major roads, railways, airports and large cities under the Environmental Noise Directive; England publishes its own road and rail maps; in the United States, the Bureau of Transportation Statistics publishes a national transportation noise map. They are modelled long-term averages, not measurements at your window, but they show where the loud corridors are.

For context, the World Health Organization's Environmental Noise Guidelines for the European Region recommend keeping average road traffic noise below 53 dB L_den (a day-evening-night average) and below 45 dB L_night at night, levels above which it found evidence of adverse health effects. Many city streets exceed them, which is why the windows and the bedroom's orientation matter so much.

Walls, floors and ceilings

Separating walls

Ask which walls are shared with other flats, and which rooms are on the other side. A bedroom against a neighbour's living room or kitchen is a common source of trouble. Knock on the shared wall: a dull, solid sound suggests masonry; a hollow, drum-like sound suggests a lightweight partition, which can be very good if it was built as a separating wall with separate layers and insulation, or poor if it was not.

Floors

Impact noise from above is the hardest to fix once you live there. Look at, or ask about, the floor in the flat above. Carpet with underlay is far quieter for the people below than hard floors; many residential leases require carpet or an acoustic underlay for this reason, but not all are enforced. In your own flat, the floor finish matters mostly to your downstairs neighbour, and to the reverberation of your rooms.

Conversions and older buildings

Flats created by dividing an older house can have floors made of timber joists and boards with little between one home and the next. Ask when and how the building was converted. Purpose-built blocks with concrete floors usually perform better against footsteps.

Windows, doors and ventilation

• Windows: close them and listen. Note whether they seal properly when shut and whether there are gaps around the frame. Double glazing helps, and secondary glazing with a wide air gap between the panes is often better still against traffic noise.
• Trickle vents and air bricks: necessary for ventilation, but they are openings. Some acoustic versions exist; ask what is fitted.
• Entrance door: a lightweight door onto a busy stairwell, with a gap underneath, lets in conversations, lift noise and the main door slamming.
• Ventilation and heating: if a flat relies on keeping windows open in summer, the closed-window quiet you hear at the viewing may not be how you live.

Simple tests during a viewing

1. Stand still and stay quiet for a minute in each room, especially the bedroom, with the windows closed and then open. Ask the agent or landlord to stop talking for that minute; it is a reasonable request.
2. Listen for building services: lifts, pumps, fans, a neighbour's washing machine or boiler on the other side of the wall.
3. Use your phone as a rough meter. Sound level apps vary in accuracy, and phone microphones are not calibrated instruments, but comparing readings between rooms or between flats on the same phone is still informative. The U.S. National Institute for Occupational Safety and Health has published its own sound level meter app.
4. Look at the neighbours' doors and windows: a baby buggy, a drum kit visible through a window, a dog barking at the door; none is a reason to walk away, but all are worth knowing.
5. Ask direct questions: have there been noise complaints? Who lives above and below? Why is the current tenant leaving? Is any construction planned nearby?
6. Talk to a neighbour if you meet one in the stairwell. They know exactly what the building sounds like.

What the building should achieve

New flats are built to minimum sound insulation standards, and knowing that a building was built to them, or before them, is useful.

• England: the building regulations' guidance, Approved Document E, sets minimum airborne sound insulation for walls and floors between new purpose-built flats (45 dB D_nT,w + C_tr) and a maximum impact sound level for floors (62 dB L'_nT,w), with slightly relaxed values for conversions. New buildings are normally tested before completion or built to approved robust details.
• United States: the International Building Code, adopted with local amendments by many states and cities, requires walls and floor-ceilings between dwelling units to have a sound transmission class (STC) of 50 and floors an impact insulation class (IIC) of 50 in laboratory tests, or 45 when tested in the field.

Older buildings may predate any such rules. Meeting the minimum also does not mean silence: loud music, bass and footsteps on hard floors can still be heard through compliant constructions.

If noise becomes a problem

Start by talking to the neighbour; many people have no idea how far their sound carries. Keep a log of dates, times and what you heard. If the source is in the building itself, such as a faulty pump or a slamming communal door, report it in writing to the landlord or managing agent.

Formal routes depend on where you live. In England, for example, councils must investigate complaints about noise from premises that may be a statutory nuisance and can serve abatement notices; road traffic and aircraft noise are generally outside those powers. Many cities elsewhere have noise ordinances with quiet hours enforced by the city. Your lease may also contain rules about noise and floor coverings that the landlord can enforce.

What you can improve without building work

A tenant can rarely change a wall or a floor, but several reversible measures help, especially with higher-pitched noise and with how loud your own rooms sound.

• Seal gaps: self-adhesive seals around the entrance door and a door sweep or draught excluder at the bottom cut corridor noise noticeably.
• Window seals: replacing tired seals, or adding removable secondary glazing panels with the landlord's agreement, helps against traffic noise.
• Heavy curtains: they help a little with high frequencies and make a room less echoey, but they do little against traffic rumble or bass.
• Rugs with underlay: they reduce the noise you send downstairs and the reverberation in your own room.
• Furniture against the shared wall: a full bookcase makes a modest difference; moving the bed away from the shared wall or to a quieter room often makes more.
• Isolate machines: rubber feet under a washing machine and speakers, and loudspeakers kept off the shared wall and off the floor, cut the vibration you pass to neighbours. Our guide to listening-room acoustics covers placement in more detail.
• Masking sound: a fan or a steady background sound can make intermittent noise less disturbing at night.

If music matters to you, the same awareness works in reverse: keep the bass reasonable, mind the hours, and remember that a modest system set up well, as in good hi-fi on a tiny budget, sounds better at sensible levels than a big one fighting the room.

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