Learn · Acoustics 101
An introduction to sound.
Sound surrounds us constantly — but what is it, and why does it behave so badly indoors? A plain-language primer.
01 · The Basics of Sound
Vibrations, moving through air.
Sound is movement. When something vibrates — a voice, a speaker cone, a closing door — it pushes against the air around it, compressing and rarefying the molecules in a rhythmic wave that radiates outward in every direction. Your ear catches that wave and your brain reads it as sound. Nothing is actually travelling across the room except the disturbance itself, passed molecule to molecule like a rumour.
Two properties describe almost everything about a sound. Its amplitude — how much the air is displaced — is what we hear as loudness; a bigger wave is a louder sound. Its frequency — how many times the wave cycles each second, measured in hertz — is what we hear as pitch; faster cycles read as higher notes. A double bass cycles slowly, a cymbal quickly.
In open air this is harmless and brief. The wave expands, loses energy, and fades. Indoors, where the same wave meets walls, glass and stone, it has nowhere to go — and that is where the trouble begins.
Term · Frequency
The number of wave cycles per second, measured in hertz (Hz). Low frequencies are deep and slow; high frequencies are bright and fast.
02 · Why Rooms Sound Bad
Hard surfaces never let go of sound.
A room is a box of reflections. When a sound wave reaches a hard, dense surface — marble, glass, concrete, gypsum — almost none of its energy is absorbed. Instead the wave bounces, and bounces again, ricocheting between parallel walls dozens of times before it finally dies. Each reflection arrives at your ear a few milliseconds after the last, smeared on top of the original sound.
This lingering is called reverberation, and a little of it is pleasant — it is why a cathedral feels grand and a shower feels resonant. Too much of it, in a working room, is exhausting. Speech loses its edges and becomes hard to follow. Music turns muddy. Open-plan offices fill with a wash of overlapping voices that no one can quite tune out.
The harder and emptier the room, the longer sound survives. A glass-walled meeting room in a Dubai tower can hold a clap for over three seconds — long after the speaker has moved on to their next sentence.
Term · Reverberation
The persistence of sound in a space after the source has stopped, caused by repeated reflections off hard surfaces.
Term · RT60
The time it takes for sound to decay by 60 decibels — effectively, how long an echo lingers. The single most useful number in room acoustics.
03 · How Absorption Works
Trading reflection for friction.
The fix is not to block sound but to absorb it. A porous material — dense felt, mineral wool, an open-celled foam — lets the sound wave enter rather than bounce off it. Inside that tangle of fibres, the moving air loses its energy to friction and heat. What goes in does not come back out. The reflection is gone, and with it the smear of reverberation.
How much a material absorbs is rated by its Noise Reduction Coefficient, or NRC — a single number from 0 to 1. A value of 0 reflects everything; a value of 1 absorbs everything. Bare drywall sits near 0.05. A heavy curtain might reach 0.4. A purpose-built acoustic panel can climb past 0.9, doing in a few centimetres of thickness what soft furnishings never could.
The art is in placing the right amount of absorption in the right places — enough to tame the reverberation, but not so much that the room goes lifeless and dead.
Term · NRC
Noise Reduction Coefficient — the fraction of sound energy a material absorbs, averaged across speech frequencies, from 0 (reflective) to 1 (fully absorptive).
04 · Before & After
The same room, measured twice.
The effect of treatment is not subjective. Point a measurement microphone at a calibrated burst of noise and you can watch the decay shorten in real time. Below is a single room recorded before and after acoustic panels were installed — the same space, the same source, the same microphone — plotted as sound level falling over time.
Before, the energy bleeds away slowly, taking more than three seconds to fall the 60 decibels that defines RT60. After, it is gone in under a second. To anyone in the room the change is immediate and physical: voices snap into focus, the strain of listening lifts, and the space simply feels calmer.
Good acoustics aren't added. They're designed in.
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