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Room Acoustics Calculator — RT60 Reverb Time (Sabine Formula)

Calculate RT60 reverb time and room modes for acoustic treatment

RT60

0.68s

Volume

85 m³

Absorption

20 sabins

Reverberation Time (RT60)

0.68s

Good for speech and small rooms

Volume

85 m³

Absorption

20

Room Modes (Axial)

Length Mode28.1 Hz
Width Mode37.5 Hz
Height Mode56.3 Hz

Example Calculations

1Home Studio (20×15×10 ft)

Inputs

Length20 ft
Width15 ft
Height10 ft
WallsDrywall
FloorCarpet
CeilingDrywall

Result

RT600.52s

Volume = 6.1×4.6×3.05 = 85.6 m³. Total absorption = walls × 0.05 + floor × 0.55 + ceiling × 0.05 = 26.6 sabins. RT60 = 0.161 × 85.6 / 26.6 = 0.52s.

2Concrete Garage (24×20×10 ft)

Inputs

Length24 ft
Width20 ft
Height10 ft
All SurfacesConcrete

Result

RT603.5s

Concrete α = 0.02. Very reverberant, needs significant acoustic treatment for music use.

Frequently Asked Questions

Q

What is RT60 and why does it matter?

RT60 is the time for sound to decay by 60 dB after the source stops. It determines how "live" or "dead" a room sounds. Studios aim for 0.3-0.5s. Lecture rooms need 0.6-0.8s. Concert halls are 1.5-2.5s.

  • Recording studio: 0.2-0.4s
  • Home studio/control room: 0.3-0.5s
  • Classroom/meeting room: 0.6-0.8s
  • Lecture hall: 0.8-1.2s
  • Concert hall: 1.5-2.5s
Room TypeIdeal RT60VolumeTreatment
Vocal booth0.2-0.3s<50 m³Heavy absorption
Control room0.3-0.5s50-150 m³Balanced absorption
Classroom0.6-0.8s150-500 m³Ceiling panels
Concert hall1.8-2.2s>5000 m³Diffusion + reflection
Q

What is the Sabine formula?

RT60 = 0.161 × V / A, where V = room volume (m³) and A = total absorption (sabins). Absorption = sum of each surface area × its absorption coefficient (α). Higher α means more absorption.

  • V = room volume in cubic meters
  • A = total absorption in sabins (m²)
  • α ranges from 0.01 (concrete) to 0.99 (anechoic wedges)
  • Formula assumes diffuse sound field
  • Works best for rooms with even absorption distribution
Q

What are room modes?

Room modes are resonant frequencies determined by room dimensions. The first axial mode = 343/(2×L) Hz where L is the dimension in meters. A 6m room has a first mode at 28.6 Hz. Modes cause bass buildup at certain frequencies.

  • Axial mode: f = 343 / (2 × dimension in meters)
  • Length mode is usually the lowest
  • Ideal: no two dimensions are equal or exact multiples
  • Bass traps treat room modes effectively
  • Tangential and oblique modes also exist but are weaker
Q

How do I reduce RT60 in a room?

Add absorptive materials: acoustic panels (α = 0.85), heavy carpet (α = 0.55), thick curtains (α = 0.50). Focus on first reflection points. For bass, use corner bass traps. 2" panels absorb 500+ Hz; 4" panels absorb 250+ Hz.

  • 2" acoustic panels: absorb 500+ Hz
  • 4" panels: absorb 250+ Hz
  • Corner bass traps: absorb below 250 Hz
  • Heavy curtains: quick, affordable treatment
  • First reflection points: most impactful placement

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Last Updated: Mar 20, 2026

This calculator is provided for informational and educational purposes only. Results are estimates and should not be considered professional financial, medical, legal, or other advice. Always consult a qualified professional before making important decisions. UseCalcPro is not responsible for any actions taken based on calculator results.

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