Reverb Room Size Estimator

Knowledge Base

How to Use the Reverb Calculator

The Reverb Calculator estimates room dimensions and reverb characteristics based on audio duration and frequency response. Use this when reverse-engineering a reverb sound or designing space for recording.

Understanding Reverb

Reverb is the collection of echoes that bounce off walls, floor, ceiling, and objects in a room. Small rooms have short, tight reverb. Large rooms have long, boomy reverb. Concert halls sound different from bedrooms.

Reverb Parameters

• Decay Time (RT60): How long sound takes to drop 60 dB after the source stops. Small room: 0.5s. Large hall: 2-3s.
• Pre-delay: Time before reverb starts. Longer pre-delay (20-80ms) sounds more spacious.
• Frequency-Dependent Decay: Low frequencies reverberate longer than highs (realistic).
• Early Reflections: First distinct bounces. Define room character.

Designing Reverb in Your DAW

Short reverb (0.5-1s) works for drums and percussion. Medium reverb (1-2s) for vocals. Long reverb (2-4s) for pads and ambient sounds. Always use pre-delay to keep source definition clear.

FAQ

Q: Should I use convolver or algorithmic reverb?
A: Convolvers sound more realistic (they're recordings of real spaces). Algorithmics are more tweakable. Use both.

Q: How much reverb is too much?
A: If you can't understand lyrics or instruments, reduce wet level. Reverb should enhance, not obscure.

Estimating and controlling reverberation

RT60 is the time taken for sound to fall by sixty decibels after the source stops. It is the standard single figure describing how live a space sounds. A recording booth aims very short, a control room somewhat longer, and a concert hall longer still, so there is no universally correct value, only a value appropriate to the use.

Sabine's equation estimates it from volume and absorption. Larger rooms hold sound longer because it travels further between surfaces, and more absorption shortens the time. The calculation assumes absorption is spread evenly, which real rooms rarely manage, so treat the figure as a guide to how much treatment to buy rather than as a measurement.

For speech, shorter is nearly always better. Reverberation arriving shortly after the direct sound is what makes a recording sound like a spare bedroom, and it cannot be removed afterwards with any convincing result. Getting close to the microphone helps by raising direct sound relative to reflected, and treatment reduces the reflected part itself.

Absorption coefficients vary with frequency, and this is where estimates diverge from reality. Thin materials absorb high frequencies effectively and low ones barely at all, so a room covered in thin foam ends up dull and still boomy. Balanced treatment needs thickness, or an air gap behind the panel, to reach lower frequencies.

Treat first reflections before covering area indiscriminately. The points where sound bounces once between source and listener carry more energy than anywhere else, and a modest amount of absorption placed there does more than a large amount spread evenly. Finding them takes a mirror and a few minutes.

Vocabulary

RT60. The time taken for sound in a room to decay by sixty decibels after the source stops. The standard measure of reverberation, quoted in seconds.

Sabine's equation. A formula estimating reverberation time from a room's volume and its total absorption. Assumes absorption is evenly distributed, so it gives a useful estimate rather than a measurement.

Absorption coefficient. How much sound a material absorbs rather than reflects, from zero for a perfect reflector to one for total absorption. Varies with frequency, which is why thin materials do little for bass.

First reflection. The point on a surface where sound bounces once on its way from source to listener. Carries more energy than later reflections, so treating those points first gives the largest improvement for the least material.

Worked example: the default room with five treatments

RT60 is the time a sound takes to fall by 60 decibels after the source stops. The tool uses the Sabine formula, which gives RT60 as 0.161 times the room volume in cubic metres, divided by the total absorption. Total absorption is the surface area times the average absorption coefficient. The default room, 5 by 4 by 2.7 metres, has a volume of 54.0 cubic metres and a surface area of 88.6 square metres.

The tool's podcast range is 0.3 to 0.5 seconds. Only light acoustic panels land inside it in this room, and untreated walls give nearly two seconds. The last column shows the absorption to add to reach 0.40 seconds, in square metres of perfectly absorbing surface. The tool divides that figure by 0.54 square metres per panel, which treats each panel as a perfect absorber. A panel with a coefficient below 1.0 absorbs less, so you need more of them.

Vocabulary

RT60. Reverberation time. The seconds a sound takes to decay by 60 decibels once its source stops. A long RT60 makes speech harder to follow and a very short one makes a room sound dead.

Absorption coefficient. The fraction of sound energy a surface absorbs, from 0 for a surface that reflects everything to 1 for one that absorbs everything. The tool asks for an average across all the surfaces in the room.