What This Poster Is
The DIN 18041:2016 compliance poster is a single-page visual reference that condenses the entire reverberation time target framework of the German room acoustics standard into a format you can pin to a site hoarding, fold into a drawing set, or open on a tablet during an inspection.
It covers the T_soll formula, all seven room categories with their k-values, the permissible tolerance band, volume limits for each category, and a pre-calculated table showing target RT60 values for typical room volumes from 50 m³ to 5,000 m³. If you work on German-specification projects, design across the DACH region, or use DIN 18041 as a benchmark for international projects, this reference eliminates the need to keep the full standard open during early design.
AcousPlan's RT60 calculator applies DIN 18041 targets automatically — enter your room volume and select your room type to get the compliant T_soll range in seconds.
Who Needs This Reference
Acoustic consultants on German projects — the T_soll formula is straightforward but the k-values are not always easy to recall in the field. Having the full table avoids errors when checking compliance during site visits or design reviews.
Architects designing schools, offices, and public buildings in Germany — DIN 18041 is referenced by most German state building codes (Landesbauordnungen) for publicly funded buildings. Understanding the room category system allows architects to flag acoustic design requirements early in the briefing process, before the consultant is engaged.
Building physicists and energy consultants — DIN 18041 intersects with DIN 4109 (sound insulation) and EN 12354 (building acoustics calculation) as part of the broader German acoustic compliance framework.
Students and junior consultants — the poster makes an efficient study reference for DIN 18041 examination questions.
The T_soll Formula
DIN 18041:2016 §6.1 defines the nominal reverberation time target as:
T_soll = 0.37 × V^(1/3) × k
Where:
- T_soll = target mid-frequency reverberation time (seconds), evaluated at 500 Hz and 1,000 Hz average
- V = room volume (m³)
- k = room category constant (see table below)
The standard permits a tolerance of T_soll ± 20% for the 500 Hz and 1,000 Hz octave bands. At lower frequencies (125 Hz and 250 Hz) the tolerance is wider: up to +30% of T_soll is permitted because low-frequency reverberation is harder to control with conventional absorption materials and has less effect on speech intelligibility.
Room Categories and k-Values
| Category | Room Type | k-Value | T_soll (200 m³) | STI Requirement |
|---|---|---|---|---|
| A1 | Music (concert, rehearsal, recital) | 1.00 | 2.17 s | Not specified |
| A2 | Speech/Presentation (lecture, court, church liturgy) | 0.51 | 1.11 s | ≥ 0.60 |
| A3 | Teaching/Conference (classroom, seminar, meeting) | 0.68 | 1.48 s | ≥ 0.65 |
| A4 | Multifunctional/Communication (open plan, foyer) | 0.80 | 1.74 s | ≥ 0.50 |
| A5 | Sport/Industry | — | ≤ 1.5 s (flat limit) | Not specified |
| B1 | Small rooms ≤ 30 m³ (offices, practice rooms) | — | ≤ 0.8 s (absolute) | — |
| B2 | Corridors, stairwells | — | ≤ 1.3 s (absolute) | — |
Note: A1 rooms use k = 1.00 but the formula yields a minimum target, not a maximum. Music rooms require reverberation — the A1 target is a lower bound. The full A1 target range is T_soll × (0.85 to 1.30).
Pre-Calculated T_soll Values by Volume
The following table shows the T_soll target at mid-frequencies for each quality class across the volume range most relevant to standard building projects. Values shown are the nominal target; apply ±20% for the compliance band.
| Volume (m³) | A1 Music | A2 Speech | A3 Teaching | A4 Multi |
|---|---|---|---|---|
| 50 m³ | 1.35 s | 0.69 s | 0.92 s | 1.08 s |
| 100 m³ | 1.70 s | 0.87 s | 1.16 s | 1.36 s |
| 200 m³ | 2.14 s | 1.09 s | 1.46 s | 1.71 s |
| 300 m³ | 2.44 s | 1.24 s | 1.66 s | 1.95 s |
| 500 m³ | 2.85 s | 1.45 s | 1.94 s | 2.28 s |
| 750 m³ | 3.19 s | 1.63 s | 2.17 s | 2.55 s |
| 1,000 m³ | 3.46 s | 1.77 s | 2.35 s | 2.77 s |
| 2,000 m³ | 4.36 s | 2.22 s | 2.96 s | 3.49 s |
| 5,000 m³ | 6.08 s | 3.10 s | 4.13 s | 4.86 s |
How to read this table: A 300 m³ German classroom (Category A3) has a T_soll of 1.66 s. The compliance range is 1.66 s ± 20%, giving a passing band of 1.33–1.99 s. The upper tolerance is typically the design constraint — anything below 1.99 s is acceptable at mid-frequencies.
In practice, most classrooms of this size achieve RT60 values of 0.5–0.8 s with suspended acoustic ceilings, which sits well within the A3 compliance band.
Frequency-Dependent Requirements
The T_soll formula and tolerance apply at mid-frequencies (500 Hz and 1,000 Hz average). DIN 18041 §6.2 specifies additional requirements for the full octave band range:
| Octave Band | Tolerance Above T_soll | Notes |
|---|---|---|
| 125 Hz | + 30% max | Low-frequency control is difficult; wide tolerance |
| 250 Hz | + 20% max | Same as mid-frequency tolerance |
| 500 Hz | ± 20% | Mid-frequency reference band |
| 1,000 Hz | ± 20% | Mid-frequency reference band |
| 2,000 Hz | + 20%, − 20% | Must not drop significantly |
| 4,000 Hz | + 30%, − 20% | High-frequency air absorption at large volumes |
The frequency-dependent tolerance captures an important physical reality: most acoustic absorption materials work better at high frequencies than low frequencies. If the mid-frequency RT60 is on target but the 125 Hz RT60 is 80% higher, the room will sound "boomy" even though it nominally passes the standard. DIN 18041's frequency-specific limits prevent this common design failure.
Volume Limits by Category
DIN 18041 applies its T_soll formula to rooms within these volume ranges:
- A1 (Music): 30 m³ to 30,000 m³
- A2 (Speech): 30 m³ to 30,000 m³
- A3 (Teaching): 30 m³ to 3,000 m³ (larger teaching rooms typically reclassified as A2)
- A4 (Multifunctional): 30 m³ to 30,000 m³
- A5 (Sport/Industry): No volume formula — flat RT60 ≤ 1.5 s regardless of volume
How DIN 18041 Fits Into the German Compliance Framework
DIN 18041 sits within a wider set of standards that German acoustic consultants apply together:
DIN 4109:2018 — Sound insulation between rooms. DIN 4109 sets the STC/Rw-equivalent targets (erf. Rw) for walls, floors, and windows. DIN 18041 governs reverberation within a room; DIN 4109 governs sound transmission between rooms. Both standards apply to most German building projects.
VDI 2058 Part 3 — Workplace noise limits. Relevant for open-plan offices where DIN 18041 A4 criteria apply alongside occupational noise regulations.
DGUV Information 215-443 — German workplace design guidelines for acoustic quality in offices, which reference DIN 18041 A4 for open-plan and meeting rooms.
DIN EN 12354 series — Calculation methods for sound insulation, reverberation, and room acoustics performance in buildings. Used for predicted compliance before construction.
How to Use This Poster
Step 1 — Classify your rooms. Go through the room schedule and assign each room to A1, A2, A3, A4, A5, B1, or B2 based on its primary use. A room that serves multiple functions (e.g., a school hall used for assembly and theatre) should be assigned the more demanding class.
Step 2 — Calculate T_soll for each room. Use the formula or read the pre-calculated table above. Record T_soll and the compliance band (T_soll ± 20%) for each room.
Step 3 — Determine required absorption. Use Sabine's equation (A = 0.161 × V / T) to calculate the total absorption area needed to achieve T_soll. Compare this against the calculated absorption from finishes and furnishings.
Step 4 — Verify with AcousPlan. Enter room dimensions and surface materials into AcousPlan's RT60 calculator. The tool calculates T_soll per DIN 18041 and shows you the compliance margin across all octave bands.
Step 5 — Check STI for A2 and A3 rooms. Categories A2 and A3 require explicit STI verification. AcousPlan calculates STI from room geometry and absorption. A3 rooms require STI ≥ 0.65; A2 rooms require STI ≥ 0.60.
Common DIN 18041 Compliance Failures
Wrong room category assigned: The most frequent cause of specification errors. A teachers' preparation room is B1 (small office); a classroom is A3. Assigning the wrong category leads to either over-specification (adding unnecessary absorption) or under-specification (failing compliance).
Mid-frequency compliance masking low-frequency failure: A room can pass T_soll at 500–1,000 Hz while having a 125 Hz RT60 that is 60–80% higher. DIN 18041 permits +30% at 125 Hz, so the room may technically comply — but it will still sound boomy. Designing for mid-frequency compliance while ignoring low frequencies is a common shortcut that leads to client complaints post-occupation.
Forgetting the STI requirement for A3: DIN 18041's STI ≥ 0.65 requirement for classrooms is mandatory but is sometimes treated as informational. In a 250 m³ classroom with RT60 = 0.7 s, background noise from HVAC at NC-35 can bring STI down to 0.58 — a fail. STI must be calculated, not assumed.
Applying A1 as an upper limit: Music rooms need reverberation. A concert hall designed to DIN 18041 A1 should achieve T_soll at minimum, not T_soll as a maximum. Using A1 as a "must not exceed" target produces acoustically dead music spaces.
Related Standards and Resources
- DIN 18041 Complete Guide — deep dive into quality classes, calculation method, worked examples
- DIN 18041 vs BS 8233 vs ISO 3382 for Classrooms — comparison across three national standards
- RT60 Calculator — Quick — calculate T_soll compliance for any DIN 18041 room category
- BB93 School Acoustics Guide — UK equivalent for school acoustic design
All T_soll values in this article are calculated per DIN 18041:2016-03 §6.1 using T_soll = 0.37 × V^(1/3) × k. AcousPlan calculations are advisory and should be verified by a qualified acoustic consultant before use in formal compliance submissions.