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Sound Isolation Calculator

STC · Transmission Loss · NC Curves · Construction

Sound Transmission Class (STC) Calculator

Transmission Loss by Frequency

Select a construction type to see its transmission loss performance across the frequency spectrum.

Mass Law Calculator

Calculate transmission loss using the mass law: TL = 20×log₁₀(mass × frequency) - 47 dB

Mass Law Guidelines

  • Doubling the mass increases TL by ~6 dB
  • Doubling the frequency increases TL by ~6 dB
  • Mass law applies above the coincidence frequency
  • Low frequencies may not follow mass law due to stiffness control

Composite Wall Calculator

Calculate overall STC when different walls have different constructions (weakest link analysis).

Wall 1

Wall 2

Door/Window STC Impact

Calculate how doors and windows affect overall wall STC performance.

Improvement Guidelines

  • Seal all gaps around doors and windows
  • Use acoustic weatherstripping
  • Consider double-entry vestibules for critical applications
  • Acoustic windows can maintain higher STC ratings

Flanking Path Analysis

Identify potential sound transmission paths that bypass the main wall assembly.

Common Flanking Paths (Check all that apply):

Flanking Path Solutions

  • Floor/Ceiling: Resilient underlayment, floating floors
  • HVAC: Duct silencers, flexible connections
  • Electrical: Acoustic putty pads, offset outlets
  • Plumbing: Acoustic wrap, resilient mounting
  • Structural: Isolation clips, resilient connections
  • Gaps: Acoustic sealant, weatherstripping

Noise Criteria (NC) Curves

Select target NC rating to see allowable noise levels across frequency bands.

HVAC Noise Calculator

Estimate noise contribution from HVAC systems based on duct size, velocity, and distance.

HVAC Noise Control

  • Keep duct velocities under 1000 ft/min for quiet spaces
  • Use duct silencers for critical applications
  • Avoid sharp bends and restrictions
  • Isolate equipment with vibration pads
  • Use flexible connections to prevent vibration transmission

Required Isolation Calculator

Calculate the required STC based on source noise level and target background level.

Room-within-Room Guidance

Design principles for maximum sound isolation using decoupled construction.

Room-within-Room Best Practices

  • Complete Decoupling: No structural connections between rooms
  • Floating Floors: Isolate floor structure from walls
  • Suspended Ceilings: Hang from inner room structure only
  • Air Gaps: Minimum 2" gap, 4-6" optimal for low frequencies
  • Absorption: Fill gaps with absorptive material (not rigid)
  • Seal Everything: All penetrations must be sealed acoustically
  • Mass + Decoupling: Combine heavy construction with isolation

Impact Insulation Class (IIC) Rating

Floor impact ratings for different assemblies and treatments.

IIC Requirements

  • IBC Minimum: IIC 50 for multi-family residential
  • FHA Requirement: IIC 45 minimum
  • Luxury Standard: IIC 60+ recommended
  • Critical Spaces: IIC 65+ for recording studios

Construction Types Database

Reference database of common wall, floor, and ceiling constructions with their STC and IIC ratings.

Construction Type STC Rating IIC Rating Thickness Notes