--- title: "Reverb Time Calculator: Sabine & Eyring RT60 | Sound Attic" description: "Estimate RT60 per octave band from 125 Hz to 4 kHz with Sabine and Eyring, from your room and its surfaces, and see how much absorption a target needs." url: https://soundattic.me/reverb-time-calculator/ --- RT60 · 125 Hz to 4 kHz # Reverb time calculator How long your room rings after a sound stops, band by band, and how much absorption it would take to tame it. ## How the estimate works Every surface soaks up part of the sound that hits it. Its **absorption coefficient** runs from 0 (reflects everything) to 1 (absorbs everything) and changes with frequency, so the calculator works band by band. Area times coefficient, added up over the room, gives the total absorption A, and Sabine’s formula turns it into a reverb time: T = 0.161 · V / A (Sabine) T = 0.161 · V / (−S · ln(1 − ᾱ)) (Eyring) V is the volume in m³, S the total surface area and ᾱ the average coefficient. Eyring always gives the shorter time; the gap grows as the room gets deader. **Treat the results as rough estimates.** Both formulas assume a diffuse sound field, with sound arriving equally from every direction. Small rooms don’t behave like that, least of all in the bass, where room modes take over. Pick materials from the published table, or choose custom coefficients and copy them from your panel’s data sheet. The target starts at ITU-R BS.1116-3’s value for a reference listening room; set your own for a live room or a vocal booth. **Buying panels online?** Before ordering acoustic panels or studio gear at a surprising discount from a shop you only know from a social media advert, check how long its domain has existed with [WebTraceCheck’s DNS and domain lookup](https://webtracecheck.com/dns-lookup). You can also open the shop’s link in [WebTraceCheck’s disposable cloud browser](https://webtracecheck.com/), which runs on an isolated desktop that is deleted after each session. ## Sources - Sabine’s T = 0.161·V/A and Eyring’s T = 0.161·V/(−S·ln(1 − ᾱ)), and the diffuse-field assumption behind them: A. Nowoświat and M. Olechowska, [Investigation studies on the application of reverberation time](https://doi.org/10.1515/aoa-2016-0002), Archives of Acoustics 41(1), 15–26 (2016). Originals: W. C. Sabine, *Collected Papers on Acoustics* (Harvard University Press, 1922); C. F. Eyring, [Reverberation time in “dead” rooms](https://doi.org/10.1121/1.1915175), J. Acoust. Soc. Am. 1(2A), 217–241 (1930). Air absorption is left out. - Absorption coefficients for building materials: D. E. Hall, *Musical Acoustics*, 2nd edition (Brooks/Cole, 1991), Table 15.1, as reproduced in R. Nave, [Modeling Reverberation Time](https://hyperphysics.gsu.edu/hbase/Acoustic/revmod.html), HyperPhysics, Georgia State University. - Glass-fibre board: Owens Corning, [Fiberglas 700 Series Board product data sheet](https://www.owenscorning.com/dms/10021736) (Pub. No. 10021736-H), Type 703 unfaced, tested to ASTM C423 with Type A mounting (against a solid backing). Coefficients above 1 come from the test method, not a fault. - Target reverb time, Tm ≈ 0.25·(V / 100 m³)^(1/3) s averaged over 200 Hz to 4 kHz, for a reference listening room: [Recommendation ITU-R BS.1116-3](https://www.itu.int/dms_pubrec/itu-r/rec/bs/R-REC-BS.1116-3-201502-I!!PDF-E.pdf) (02/2015), §8.2.3.1. The averages here use the 250 Hz to 4 kHz octave bands, the nearest octave-band match. - Feet and square feet: [NIST Special Publication 811](https://www.nist.gov/pml/special-publication-811) (1 ft = 0.3048 m). | Material | 125 | 250 | 500 | 1k | 2k | 4k | Source | | --- | --- | --- | --- | --- | --- | --- | --- | | Acoustic tile, rigid mount | 0.20 | 0.40 | 0.70 | 0.80 | 0.60 | 0.40 | Hall | | Acoustic tile, suspended | 0.50 | 0.70 | 0.60 | 0.70 | 0.70 | 0.50 | Hall | | Acoustical plaster | 0.10 | 0.20 | 0.50 | 0.60 | 0.70 | 0.70 | Hall | | Ordinary plaster, on lath | 0.20 | 0.15 | 0.10 | 0.05 | 0.04 | 0.05 | Hall | | Gypsum wallboard, ½ in on studs | 0.30 | 0.10 | 0.05 | 0.04 | 0.07 | 0.10 | Hall | | Plywood sheet, ¼ in on studs | 0.60 | 0.30 | 0.10 | 0.10 | 0.10 | 0.10 | Hall | | Concrete block, unpainted | 0.40 | 0.40 | 0.30 | 0.30 | 0.40 | 0.30 | Hall | | Concrete block, painted | 0.10 | 0.05 | 0.06 | 0.07 | 0.10 | 0.10 | Hall | | Concrete, poured | 0.01 | 0.01 | 0.02 | 0.02 | 0.02 | 0.03 | Hall | | Brick | 0.03 | 0.03 | 0.03 | 0.04 | 0.05 | 0.07 | Hall | | Vinyl tile on concrete | 0.02 | 0.03 | 0.03 | 0.03 | 0.03 | 0.02 | Hall | | Heavy carpet on concrete | 0.02 | 0.06 | 0.15 | 0.40 | 0.60 | 0.60 | Hall | | Heavy carpet on felt backing | 0.10 | 0.30 | 0.40 | 0.50 | 0.60 | 0.70 | Hall | | Platform floor, wooden | 0.40 | 0.30 | 0.20 | 0.20 | 0.15 | 0.10 | Hall | | Ordinary window glass | 0.30 | 0.20 | 0.20 | 0.10 | 0.07 | 0.04 | Hall | | Heavy plate glass | 0.20 | 0.06 | 0.04 | 0.03 | 0.02 | 0.02 | Hall | | Draperies, medium velour | 0.07 | 0.30 | 0.50 | 0.70 | 0.70 | 0.60 | Hall | | Glass-fibre board 25 mm (1 in), Owens Corning 703 | 0.05 | 0.26 | 0.63 | 0.88 | 0.97 | 0.94 | Owens Corning | | Glass-fibre board 51 mm (2 in), Owens Corning 703 | 0.15 | 0.71 | 1.14 | 1.16 | 1.02 | 1.00 | Owens Corning | | Glass-fibre board 76 mm (3 in), Owens Corning 703 | 0.34 | 1.09 | 1.25 | 1.15 | 1.05 | 1.00 | Owens Corning | | Glass-fibre board 100 mm (4 in), Owens Corning 703 | 0.56 | 1.26 | 1.22 | 1.11 | 1.07 | 0.96 | Owens Corning | ## Questions **Why does the bass stay long when I add panels?** Thin panels absorb little low down. In the Owens Corning data, 25 mm board has a coefficient of 0.05 at 125 Hz against 0.56 for 100 mm. Thicker panels, or panels spaced off the wall, reach lower. **Which result should I trust, Sabine or Eyring?** Neither exactly. They agree when a room is fairly live and drift apart as it gets deader, where Eyring is the better model. In a small room, use them to compare one treatment plan with another, and measure for real numbers. **What target should a home studio aim for?** The default is the value BS.1116-3 gives for reference listening rooms, which are built for critical listening tests; in a small room it is short. Use it as a goal for a mixing room, and set your own for a room you want to sound live.