Sarooma Alternative — Free Acoustic Design With ISO 3382 Compliance

42% of architects surveyed in a 2025 RIBA report said they perform no acoustic analysis during schematic design — not because acoustics is unimportant, but because the available tools are either too expensive (ODEON at $2,800/year, EASE at $3,500/year) or too complex for occasional use. Freemium acoustic tools like Sarooma and AcousPlan exist to close that gap. Both offer browser-based RT60 calculation at no cost. But beneath the shared "free RT60 calculator" positioning, the two platforms differ substantially in database depth, compliance automation, and design workflow support.

This article provides an honest comparison of Sarooma and AcousPlan for architects and consultants evaluating free acoustic design tools.

What Sarooma Offers

Sarooma is a web-based acoustic design tool that provides RT60 calculation with a freemium pricing model. The platform targets architects and interior designers who need quick reverberation time estimates without investing in professional acoustic software.

Core Features

RT60 calculation: Sarooma calculates reverberation time using the Sabine equation (ISO 3382-2:2008 §A.1). Users input room dimensions, select surface materials from a dropdown library, and receive an RT60 prediction across frequency bands.

Room type presets: Pre-configured room templates (office, classroom, restaurant, etc.) with default dimensions and surface finishes that users can modify.

Material library: Sarooma includes a curated set of acoustic materials with absorption coefficients. The library is smaller than professional databases but covers common architectural finishes.

Visual feedback: Graphical display of RT60 across frequency bands, showing the reverberation curve against target values for the selected room type.

Report export: Basic report generation showing room parameters and RT60 results.

Sarooma's Strengths

Simplicity: The interface is clean and focused. An architect unfamiliar with acoustic software can produce a first result within minutes. The learning curve is minimal.

Quick estimates: For a preliminary check — "Will this room need acoustic treatment?" — Sarooma provides a fast answer without configuration overhead.

Free tier: The basic RT60 calculation is available without payment, making it accessible for occasional users.

Sarooma's Limitations

Material database size: Sarooma's material library includes approximately 50-100 materials with generic absorption data. Products are not linked to specific manufacturers, and there is no cost or carbon information.

No automated compliance checking: Sarooma calculates RT60 but does not automatically compare results against building codes (BB93, DIN 4109, NCC, IBC) or certification standards (WELL v2 Feature 74). Users must know the applicable limits and perform the comparison manually.

Limited STI prediction: Speech intelligibility calculation is basic or absent, depending on the tier. The IEC 60268-16:2020 modulation transfer function method requires background noise levels and signal-to-noise ratios that Sarooma does not incorporate.

No sound insulation: Sarooma focuses on room acoustics (absorption, RT60). Sound insulation calculation (STC/Rw through walls and floors) is outside its scope.

No AI assistance: Sarooma does not include automated treatment recommendation, AI-guided material selection, or diagnostic chatbot capabilities.

No floor plan import: Users must manually enter room dimensions. There is no image-based room detection or IFC/BIM import.

Feature Comparison: Sarooma vs AcousPlan

Materials Database: The Critical Difference

The gap between 50-100 generic materials and 5,678 manufacturer-specific products has practical consequences at every stage of the acoustic design workflow.

Specification Accuracy

Generic material data uses averaged absorption coefficients — "mineral wool ceiling tile" might be assigned α₅₀₀ = 0.85 as a category average. But real products within this category vary significantly:

The NRC spread is 0.70 to 0.90 — a 29% variation within a single material category. Using a generic average can produce RT60 predictions that deviate by 15-20% from what the installed product will deliver. In a room near the compliance threshold (e.g., RT60 = 0.58 s against a 0.60 s target), this error margin can flip the prediction from pass to fail.

Cost Comparison Capability

Sarooma tells you that a room needs acoustic ceiling treatment. AcousPlan tells you that:

• Option A (Ecophon Focus Ds): meets target at €42/m², 3.8 kg CO₂e/m²
• Option B (Rockfon Blanka A24): meets target at €38/m², 4.2 kg CO₂e/m²
• Option C (Knauf AMF Thermatex Alpha): does NOT meet target — insufficient absorption
• Option D (Armstrong Optima): meets target at €45/m², 3.5 kg CO₂e/m²

Worked Example: 60 m² Classroom

Room dimensions: 8 m × 7.5 m × 3 m (volume = 180 m³). Finishes: plasterboard ceiling, three painted plaster walls, one wall with glazing (7.5 m × 3 m), vinyl floor. Standard: BB93:2015 (UK school acoustics) requires RT60 ≤ 0.60 s for a secondary school teaching space of this volume, per Table 1.1.

Baseline Calculation

Per ISO 3382-2:2008 §A.1 (Sabine equation):

RT60 = 0.161 × 180 / 7.49 = 3.87 s — drastically above the BB93 target of 0.60 s.

This room is far from compliance because the vinyl floor (unlike carpet) provides almost no absorption. The ceiling and all walls are reflective.

Treatment Required

Target absorption: A = 0.161 × 180 / 0.60 = 48.3 m² Sabins at 500 Hz

Additional absorption needed: 48.3 − 7.49 = 40.8 m² Sabins

Ceiling treatment only (replacing plasterboard with Rockfon Blanka A24, α₅₀₀ = 0.90):

Additional absorption from ceiling = 60.0 × (0.90 − 0.06) = 50.4 Sabins

New total: 7.49 + 50.4 = 57.89 Sabins

New RT60 = 0.161 × 180 / 57.89 = 0.50 s — BB93 PASS

Sarooma Workflow

1. Enter dimensions (1 minute)
2. Select generic "plasterboard" ceiling, "vinyl" floor, "plaster" walls, "glazing" (2 minutes)
3. Read RT60 result (1 minute)
4. Manually look up BB93 Table 1.1 for the applicable limit (5 minutes if unfamiliar with BB93)
5. Manually determine that the room fails
6. Manually select a replacement ceiling material from the generic list (3 minutes)
7. Re-calculate and re-check manually against BB93 (2 minutes)

AcousPlan Workflow

1. Enter dimensions (30 seconds)
2. Select room type "Classroom — Secondary School" (10 seconds)
3. Assign surface materials from database (45 seconds)
4. Read result: RT60 = 3.87 s, BB93 FAIL displayed automatically (0 seconds)
5. Click "Auto-Solve" → engine recommends three ceiling options with cost and carbon (10 seconds)
6. Select preferred option → RT60 recalculates to 0.50 s, BB93 PASS (5 seconds)
7. Click "Generate Report" → PDF with compliance statement, material spec, cost estimate (10 seconds)

Compliance Automation: The Workflow Multiplier

For a single room, the time difference between manual and automated compliance checking is minutes. For a multi-room project — a new school with 20 classrooms, 4 music rooms, 2 drama studios, a dining hall, and administrative offices — the difference is hours.

BB93:2015 specifies different RT60 targets for each room type:

• Primary school classroom: 0.60 s (furnished, unoccupied)
• Secondary school classroom: 0.60 s
• Open plan teaching area: 0.80 s
• Music room: 1.00 s
• Drama studio: 0.60-0.80 s (depends on use)
• Dining room: 0.80-1.20 s (depends on volume)
• Sports hall: 1.50-2.00 s

Across a 30-room school project, automated compliance checking saves approximately 3-5 hours of standard lookup and manual comparison.

Features Unique to AcousPlan

Snap & Solve Floor Plan Analysis

Upload a floor plan image (JPG, PNG, PDF), and AcousPlan's AI extracts room dimensions, identifies probable surface materials from the drawing notation, and calculates RT60 for each identified room. This workflow is valuable during feasibility studies when dimensions are available only as architectural drawings, not as parametric inputs.

AI Acoustic Chatbot

AcousPlan includes a Claude-powered chatbot that answers acoustic design questions with standard citations. Example queries:

• "What is the BB93 RT60 requirement for a primary school music room?"
• "Which ceiling tile would reduce RT60 from 1.2 s to 0.6 s in a 200 m³ room?"
• "What is the difference between NRC and αw?"

Sound Insulation Calculator

Many projects require both room acoustic assessment (RT60, absorption) and sound insulation specification (STC/Rw). A school project under BB93 must address both reverberation in teaching spaces and airborne sound insulation between classrooms. AcousPlan covers both in a single platform with 52 wall and floor assemblies rated per ASTM E90/E413 (STC) and ISO 717-1 (Rw).

Browser-Based Auralization

AcousPlan generates real-time auralization previews using the Web Audio API. Users can hear how a room sounds before and after treatment — a powerful communication tool for explaining acoustic treatment value to non-technical stakeholders. Multi-source binaural rendering (up to 5 sources with HRTF processing) is available on the Pro tier.

Multilingual Interface

AcousPlan supports 27 languages including German, French, Spanish, Japanese, Chinese, Korean, Arabic (RTL), and Hindi. For international practices or consultancies serving non-English-speaking clients, the localised interface removes a barrier to adoption.

When Sarooma Is Sufficient

Sarooma is a reasonable choice when:

• You need a quick RT60 estimate and already know the applicable compliance target
• Your projects are limited to a single room type where you have memorised the standard requirements
• Generic material data is acceptable (you will specify manufacturer products separately)
• You do not need compliance reports, cost estimates, or carbon assessments
• Sound insulation is outside your project scope
• Your team works exclusively in English

Sarooma's Sweet Spot

A solo interior designer checking whether a restaurant renovation needs acoustic treatment. The designer knows that restaurant RT60 should be below 0.80-1.00 s from experience. Sarooma provides a quick calculation to confirm or deny the need for treatment. If treatment is needed, the designer will consult an acoustic specialist for the detailed specification.

When AcousPlan Is the Better Choice

AcousPlan is the stronger choice when:

• You work across multiple building codes and need automated compliance checking
• Brand-specific material specification matters for your construction documentation
• Cost and carbon data influence design decisions
• Multi-room projects require efficient batch assessment
• Sound insulation is part of the project scope
• You need professional compliance reports for planning submissions or WELL certification
• AI-assisted design tools add value to your workflow
• Your practice is multilingual or serves international clients

AcousPlan's Sweet Spot

An architectural practice handling a WELL v2 certification for a 15-floor office building. Each floor has 8-12 room types requiring WELL v2 Feature 74 compliance documentation. The practice needs automated RT60 calculation, compliance checking against WELL targets, material specification with cost estimates, and branded PDF reports for the WELL assessor — all from a single platform, without learning acoustic engineering.

Related Reading

• Free Acoustic Software Comparison — full comparison of free-tier acoustic tools
• Best Acoustic Design Software 2026 — market overview including both free and premium tools
• What Is NRC? Noise Reduction Coefficient Explained — understanding absorption ratings used in material selection