Theoretical reference + browser-based calculation tools
Understand room acoustics, explore estimates, and plan what to measure.
Explore room modes, speaker placement and reverberation with worked examples and interactive models. Calculated estimates, external references and site measurements are labeled separately. The 6 published guides currently publish theoretical explanations and proposed verification methods, with no completed site field tests.
Open 3D Room Mode, Schroeder & 38% Placement PlannerOpen 24-Material Octave-Band Absorption & RT60 Matrix
What the numbers mean
- Calculated estimates: model outputs based on your inputs and stated assumptions.
- Reference data: background sources and provisional material values; all 24 material rows still need matching original reports.
- Site measurements: require documented setup, raw data and limitations. The guides' proposed experiments are not completed measurements.
Static HTML acoustic reference matrices + 100% browser-local calculators
Both workbenches include reference tables and default outputs in static HTML. Browser-based calculators estimate room modes, boundary-interference frequencies, listening geometry and Sabine/Eyring RT60. The material coefficients are provisional reference values, not verified laboratory results published by this site.
Static HTML Matrix + Local Solver
Small Room Axial/Tangential/Oblique Standing-Wave Mode, Schroeder Frequency & 38% Listening Geometry Planner
Static Bolt/Sepmeyer/Louden room ratio tables and interactive 3D Rayleigh eigenfrequency solver computing axial, tangential, and oblique room modes (20–300 Hz), Schroeder crossover frequency, SBIR quarter-wave front-wall cancellation nulls, and 38% equilateral monitor coordinates.
Static HTML Matrix + Local Solver
Acoustic Material Octave-Band Absorption Coefficient (125 Hz – 4000 Hz) & Air-Gap Reference Matrix
Provisional 24-material reference matrix (original report verification incomplete) (Owens Corning 703/705, Rockwool Safe’n’Sound & Comfortboard 80, acoustic foam, PET felt, drywall, concrete, glazing, carpet) with octave-band Sabine coefficients, NRC, gas flow resistivity (Pa·s/m²), and live Sabine/Eyring RT60 estimator.
Four physical wave equations that govern every small room
1. Rayleigh 3D standing-wave eigenfrequencies
The ideal rectangular-room equation estimates axial, tangential and oblique mode frequencies. Actual peak levels and decay depend on boundaries, losses and source/receiver positions; the calculator does not predict them.
2. Schroeder crossover & SBIR quarter-wave nulls
The Schroeder frequency (f_s = 2000·√(RT60/V)) estimates a transition region. The front-wall expression f_null = c / (4·d) is a simplified starting point; the placement tool also estimates reflection path differences for the chosen geometry.
3. Particle-velocity maxima & gas flow resistivity
Ideal pressure and velocity patterns help explain why mounting and thickness matter. They do not establish a product's absorption coefficient or a fixed improvement from adding an air gap; that requires an appropriate material model or matching measurements.
4. Sabine vs. Eyring reverberation estimates
The material matrix compares Sabine and Norris-Eyring reverberation estimates using room volume, surface area and absorption coefficients. Its provisional inputs and diffuse-field assumptions limit how the results apply to a real room.
In-depth small-room acoustics & treatment monographs (6 articles)
Each guide explains a physical or geometrical model and states its scope, source limitations and proposed verification. Browse all 6 published guides by category.
Standing Waves & Modal Geometry
Axial, Tangential, and Oblique Room Modes: The Rayleigh Standing-Wave Equation
Derive Lord Rayleigh’s 3D standing-wave eigenfrequency equation, map pressure antinodes and velocity nodes, and compare axial, tangential, and oblique room modes.
Schroeder Crossover Frequency: Where Wave Acoustics Transitions to Ray Acoustics
Derive Manfred Schroeder’s modal transition frequency (f_s = 2000 × sqrt(RT60 / V)), understand modal density (dN/df), and divide small-room acoustics into four frequency zones.
Porous Absorbers & Bass Traps
Panel Air Gaps: Quarter-Wavelength Theory, Mounting Depth and Limits
Explore ideal pressure and particle-velocity patterns near a rigid wall, and distinguish air-gap geometry from measured material absorption.
Porous Absorber Gas Flow Resistivity: When Thick Low-Density Rockwool Beats Dense Fiberglass
Understand specific gas flow resistivity (σ in Pa·s/m²), the Delany-Bazley acoustic impedance model, and why low-density mineral wool outperforms dense boards in thick bass traps.
Monitor Placement, SBIR & Reflections
Speaker-Boundary Interference Response (SBIR): Quarter-Wave Cancellation From Front Walls
Derive the quarter-wavelength SBIR cancellation equation (f_null = c / 4d), understand why studio monitors radiate omnidirectionally below 250 Hz, and solve front-wall dips.
The 38% Listening Position Rule and Equilateral Monitor Triangle Geometry
Understand Wes Lachot’s 38% front-wall listening position rule, avoid the 50% and 25% axial modal nulls, and calculate 60-degree equilateral monitor triangle coordinates.