# Acoustics: how a room sounds, not just looks > How sound travels, why rooms echo, what absorbs it, and how to keep it out of the next room. Source: https://guide.rayon.design/knowledge/foundations/acoustics · Foundations · Updated 2026-10-18 © 2026 Rayon. Quote short excerpts with a link to the source page. Full terms: https://guide.rayon.design/about ## Introduction A room is heard as much as it is seen. Sound travels through air and through the building itself, rooms make it linger or fade, surfaces reflect or absorb it, and walls, floors and doors decide what reaches the next room. Learn how each works, and a home can be calm without feeling dead. ## Sound basics Understanding what we hear. Sound begins as a vibration and travels through air or through solid materials. Its frequency, measured in hertz (Hz), is its pitch: low frequencies sound deep, high ones sound sharp. Its sound pressure level, measured in decibels (dB), is how strong the pressure changes are; how loud it seems also depends on its pitch and on who is listening. Voices and music travel as [airborne sound](https://guide.rayon.design/lexicon/airborne-sound). Footsteps, slammed doors and running machines shake the structure itself as [impact sound](https://guide.rayon.design/lexicon/impact-sound), which travels through floors and walls before it is heard in another room. Find the source and its path first: each path needs its own answer. *Interactive diagram:* A voice travels through the air to a listener; a footstep travels through the floor into the room below. *Interactive diagram:* One sound wave: across sets its frequency, how many waves fit; up and down sets its amplitude, how tall they are. ### Frequency **Hz** Pitch. Speech sits mostly between about 250 and 4000 Hz. ### Sound level **dB** Strength. A quiet bedroom is about 30 dB; conversation about 60. ### Reverberation **RT60** Seconds for a sound to fall by 60 dB once it stops. ### Absorption **NRC** From 0, all reflected, to 1, all absorbed, averaged over speech pitches. ## Sound within a room Why some rooms sound lively and others quiet. We hear a sound directly from its source and again as it reflects off every surface around us. Those reflections pile up into [reverberation](https://guide.rayon.design/lexicon/reverberation): sound that lingers after its source has stopped. Reverberation time is how long it takes to fall by 60 dB. Volume, finishes, furniture and people all change it. Large rooms with hard surfaces hold sound longest; absorbent surfaces let it fade fast. The right amount depends on the use: talking wants clear speech and a short time, while some music wants a longer, fuller one. *Interactive diagram:* The same room bare and treated: one sound bounces on and on in the bare room and fades fast in the treated one. *Point across the figure to move through time after one sound: it keeps bouncing in the bare room and stops at the panel in the treated one.* ### Living room **0.4–0.6 s** Clear for talking, still warm. Rugs, a sofa and curtains usually get it there. ### Bedroom **0.3–0.5 s** The softest room in the home: bedding and textiles do most of the work. ### Open kitchen and living **0.5–0.7 s** Hard worktops and floors push it up; an acoustic ceiling brings it down. ## Materials and absorption Choosing surfaces that control reflected sound. Hard, smooth finishes such as glass, stone and concrete reflect most of the sound that reaches them. Porous and fibrous materials absorb part of it, so less comes back into the room: acoustic ceilings, wall panels, curtains and upholstery all help. Absorption changes with pitch, thickness and how the material is fixed. A thin fabric and a thick panel can look alike and behave very differently, and a panel held off the wall absorbs more of the low notes than the same panel glued flat. The [noise reduction coefficient](https://guide.rayon.design/lexicon/noise-reduction-coefficient) (NRC) sums absorption over the speech range in one number. Compare tested products and build-ups: how a surface looks says nothing about how it absorbs. *Interactive diagram:* A hard wall, a thin textile and a backed panel: how much sound each reflects and absorbs, at a low, mid or high pitch. *Point left, centre or right for a low, mid or high pitch. The ray back is the sound reflected; the column under each sample is the sound absorbed.* ### Painted plaster or glass **0.05** Typical NRC. Almost everything comes back into the room. ### Heavy curtain, gathered **0.5** Typical NRC. [Fullness](https://guide.rayon.design/lexicon/fullness) and a gap behind it help. ### Acoustic panel, 50 mm **0.8–0.95** Typical NRC, mounted with a gap behind. Check the tested figure. ## Sound between spaces Designing for quiet and privacy. Sound reaches the next room through a wall, through gaps around it, and round it through the floors, ceilings and walls that connect the two rooms: these are [flanking paths](https://guide.rayon.design/lexicon/flanking-path). A strong wall still fails if a door, an opening or a joint lets sound past it. Start with the [plan](https://guide.rayon.design/lexicon/plan): keep noisy rooms away from those that need quiet. Then treat the whole enclosure: walls, floors, doors, seals and every pipe and cable that passes through. And keep the two jobs apart: absorption calms the sound inside a room; insulation stops it reaching the next one. Each needs its own answer. *Interactive diagram:* Sound leaves one room three ways: through the wall, under the door, and round the wall through the floor. *Point at the wall, the door or the floor to follow each path from the speaker into the next room.* ### Absorption, inside a room Soft, porous surfaces, rugs, curtains and panels reduce echo and make speech clearer. They do little to stop sound reaching the next room. ### Insulation, between rooms Mass, airtight seals, separate layers and resilient fixings stop sound passing. A gap under a door can undo much of a good wall. ## Questions What people ask most about sound at home. ### How do I soundproof a room? Soundproofing stops sound passing between spaces, and it relies on three things: mass, airtightness and separation. Seal gaps first, around doors, windows and sockets. Then add mass, such as an extra layer of dense plasterboard, and, where you can, separate the new layer from the old wall on resilient fixings with insulation in the gap. Soft furnishings reduce echo inside the room, but they do little to stop sound getting out. ### How do I soundproof a door? Most noise passes around a door, not through it. Fit seals around the frame and an automatic drop seal or a [threshold](https://guide.rayon.design/lexicon/threshold) at the bottom. A solid-core or acoustic door blocks far more sound than a hollow one. ### How do I soundproof windows? Seal the frame with acoustic sealant and replace worn gaskets. Laminated acoustic glass, or secondary glazing with a gap of 10 cm or more from the existing window, makes the biggest difference. Heavy, lined curtains help a little, mostly with higher pitches. ### How do I soundproof a wall? Add mass and decouple it: fix a second layer of dense or acoustic plasterboard on resilient bars or an independent frame, with mineral wool in the cavity. Seal every edge and box in the back of sockets, because small holes let a lot of sound through. ### How do I block noise from outside? Start with the windows and doors, the weakest parts of any wall: seal them, then upgrade to acoustic glazing or secondary glazing. Fill gaps around pipes and vents, fit acoustic trickle vents, and place bedrooms on the quieter side when you can [plan the layout](https://guide.rayon.design/knowledge/foundations/use). ### How do I soundproof an apartment as a renter? Focus on what you can remove later: door seals, draught strips, heavy lined curtains, thick rugs with dense underlay, and bookcases full of books against shared walls. These reduce noise and echo noticeably, even though they cannot fully stop low-pitched sound. ### How do I reduce echo in a room? Echo comes from hard, parallel surfaces bouncing sound back and forth. Add soft, porous materials: a large rug, upholstered furniture, curtains, cushions, full bookshelves and acoustic panels. Spread them across different surfaces, including the ceiling in large rooms, rather than putting all of them on one wall. ### Do acoustic panels work? Yes, for echo inside a room: they absorb sound and shorten reverberation, so speech and music sound clearer. They do not soundproof, so they will not stop noise passing to the next room. Place them where sound first reflects, opposite or beside the people talking, and cover about 15 to 30 percent of the wall area. ### How do I soundproof a ceiling from noisy neighbours? Impact noise from footsteps is best stopped at its source, with a soft underlay or carpet upstairs. From below, add a new ceiling hung on resilient bars or acoustic hangers, with mineral wool above it and two layers of dense plasterboard, sealed at the edges. ### How do I soundproof a floor? Lay an acoustic underlay or a floating floor that sits on a resilient layer, so footsteps do not shake the structure. Rugs with dense felt pads help further. For airborne noise from below, add mineral wool between the joists and seal any gaps at the edges.