Room Acoustics Calculator

Calculate room reverberation time, identify room modes, and get recommendations for speaker placement and acoustic treatment based on your room’s dimensions and materials.

How to Use This Calculator

1. Enter room dimensions (length, width, height)
2. Select room surface materials
3. Input listening position
4. The calculator will provide:
   • Reverberation time (RT60)
   • Room modes analysis
   • Speaker placement recommendations
   • Acoustic treatment suggestions

Understanding Room Acoustics

Reverberation Time (RT60)

RT60 is the time it takes for sound to decay by 60 decibels after the source stops. Optimal RT60 varies by room use:

• Recording studios: 0.2-0.4 seconds
• Home theaters: 0.3-0.5 seconds
• Living rooms: 0.4-0.6 seconds
• Concert halls: 1.5-2.5 seconds

Room Modes

Standing waves that occur at specific frequencies based on room dimensions:

• Axial modes (between parallel surfaces)
• Tangential modes (involving four surfaces)
• Oblique modes (involving all six surfaces)

Surface Materials and Absorption

Common Materials and Coefficients

Walls

• Painted concrete: 0.01-0.02
• Drywall: 0.02-0.05
• Wood paneling: 0.10-0.30
• Acoustic panels: 0.50-0.90

Floor

• Concrete: 0.01-0.02
• Hardwood: 0.05-0.10
• Carpet: 0.20-0.45
• Heavy carpet: 0.35-0.70

Ceiling

• Painted concrete: 0.01-0.02
• Acoustic tile: 0.50-0.90
• Suspended ceiling: 0.40-0.70

Speaker Placement Guidelines

Distance from Walls

• Front wall: 2-3 feet minimum
• Side walls: 3-4 feet minimum
• Equal distances from side walls
• Avoid placing directly in corners

Listening Position

• 38% rule for room length
• Equilateral triangle with speakers
• Ear height at tweeter level
• Avoid room center points

Acoustic Treatment Recommendations

Bass Traps

• Room corners (tri-corner)
• Wall-ceiling junctions
• Wall-wall junctions
• Behind speakers

Absorption Panels

• First reflection points
• Rear wall
• Ceiling reflection points
• Front wall (behind speakers)

Diffusion

• Rear wall (if > 15 feet)
• Side walls (mid/rear)
• Ceiling (if high enough)

Room Mode Calculations

Frequency Formula

f = (c/2) × √[(l/L)² + (m/W)² + (n/H)²] Where:

• c = speed of sound (1130 ft/s)
• L = room length
• W = room width
• H = room height
• l,m,n = mode numbers (0,1,2,…)

Frequently Asked Questions

What is the ideal reverberation time?

Ideal reverberation time depends on room use:

• Critical listening: 0.2-0.4s
• Home theater: 0.3-0.5s
• Music playback: 0.4-0.6s
• Live music: 0.8-2.0s

How do I identify room modes?

Room modes can be identified by:

• Using a frequency generator
• Playing sine sweeps
• Using measurement software
• Calculating modal frequencies

Where should I place acoustic treatment?

Priority treatment locations:

1. Bass traps in corners
2. First reflection points
3. Front wall absorption
4. Ceiling reflection points
5. Rear wall treatment

How much treatment do I need?

Treatment coverage guidelines:

• Minimal: 15-25% of wall surface
• Moderate: 25-40% of wall surface
• Heavy: 40-60% of wall surface
• Critical: >60% of wall surface

Treatment Types and Applications

Absorption

1. Porous Absorbers

   • Fiberglass panels
   • Mineral wool
   • Acoustic foam
   • Purpose: Mid/high frequency control

2. Membrane Absorbers

   • Wood panels
   • Drum membranes
   • Purpose: Low frequency control

3. Resonant Absorbers

   • Helmholtz resonators
   • Slat absorbers
   • Purpose: Specific frequency control

Diffusion

1. Surface Diffusers

   • Quadratic diffusers
   • Primitive root diffusers
   • Binary amplitude diffusers
   • Purpose: Scatter reflections

2. Geometric Diffusers

   • Pyramidal diffusers
   • Polycylindrical diffusers
   • Purpose: Broad spectrum diffusion