Acoustics Calculators
6 free acoustics calculators — standards-based, with formulas, worked examples, and no sign-up.
Acoustics questions come in three shapes: how loud is it, how long does the room ring, and what will actually make it quieter. For loudness, the sound level distance calculator handles inverse-square attenuation, the power-to-pressure (Lw → Lp) conversion with directivity Q, and decibel addition of multiple sources — the bookkeeping that dB arithmetic gets wrong when done intuitively. Workplace noise gets the regulatory treatment: OSHA (5 dB exchange rate, 90 dBA criterion) and NIOSH (3 dB, 85 dBA) dose calculations to TWA with an action-level check, which matters because the two systems can disagree on the same shift.
For rooms, the reverberation time tool runs both Sabine and Eyring through a total-absorption inventory and grades RT60 against use-based targets, while the room mode calculator maps axial, tangential, and oblique modes below the Schroeder frequency and flags coincidences — the low-frequency problems absorption panels alone will not fix. For blocking sound, the acoustic calculator covers transmission loss and STC ratings across a material library, and the noise barrier tool implements Maekawa's Fresnel-number method for insertion loss, with the line-of-sight check that decides whether a barrier can work at all.
All Acoustics Tools
Acoustic Calculator
Sound transmission, absorption, and acoustic properties for glass, concrete, and composite materials.
Reverberation Time Calculator (RT60)
Room reverberation time RT60 by the Sabine (0.161 V / A) and Eyring formulas from room volume, surface areas and absorption coefficients, with total absorption in sabins, mean absorption coefficient, and an assessment against a target RT for the intended room use.
Noise Exposure Calculator (OSHA & NIOSH Dose / TWA)
Occupational noise dose and 8-hour TWA from up to twelve exposure periods (dBA level and hours), under OSHA 29 CFR 1910.95 Appendix A (90 dBA criterion, 5-dB exchange rate, TWA = 16.61 log10(D/100) + 90, action level at 50% dose / TWA 85 dBA triggering a hearing conservation program per 1910.95(c), PEL exceeded above 100% dose) or NIOSH Publication 98-126 (85 dBA REL, 3-dB exchange rate, TWA = 10.0 log10(D/100) + 85 as printed, REL reached at a dose of 100%), with per-period allowed exposure times, boundary-safe dose formatting, and a dose-contribution bar chart.
Room Mode Calculator (Axial, Tangential & Oblique)
Rectangular-room standing-wave frequencies f = (c/2) sqrt((p/Lx)^2 + (q/Ly)^2 + (r/Lz)^2) with c = 343 m/s (20 degC), enumerated completely up to 300 Hz and sorted by frequency: axial, tangential, and oblique classification, near-coincidence flags for adjacent modes spaced closer than 5% of the lower frequency, dimensions in meters or feet (1 ft = 0.3048 m exact), a frequency-strip chart of the modal stack colored by type, and the Schroeder frequency f_s = 2000 sqrt(RT60/V) when an optional reverberation time is entered.
Sound Level Distance Calculator (Attenuation, Lw → Lp & dB Addition)
Free-field sound level toolkit in three modes: distance attenuation L2 = L1 − 20 log10(r2/r1) for a point source (−6 dB per doubling) or 10 log10(r2/r1) for a line source (−3 dB per doubling) with honest gains toward the source and a level-vs-distance chart from r1 to 10·r1; sound power to sound pressure Lp = Lw + 10 log10(Q/(4πr²)) with directivity Q = 1 (free space), 2 (hard surface), 4 (wall-floor edge), or 8 (corner); and energetic addition of up to twenty incoherent levels L = 10 log10 Σ 10^(Li/10) with the increase above the loudest single source. Distances in meters or feet (1 ft = 0.3048 m exact).
Noise Barrier Calculator (Maekawa Insertion Loss)
Barrier insertion loss for a point source via the Maekawa relation IL = 10 log10(3 + 20N), Fresnel number N = 2δ/λ with λ = 343/f at 20 degC, from the exact 2-D section geometry (source height and distance, barrier top height, receiver height and distance, octave bands 63-8000 Hz): strict line-of-sight break test — a barrier exactly at grazing gets no credit — the FHWA Noise Barrier Design Handbook practical cap of 20 dB for thin walls, a live section sketch of source, barrier, receiver, and sightline, heights and distances in meters or feet (1 ft = 0.3048 m exact), and an optional source level for the resulting relative level after the barrier credit.
Frequently Asked Questions
Absorption or mass — which fixes my noisy room?
Depends whether the sound is born in the room or coming through the wall. Echoey, harsh rooms need absorption: run reverberation time and add material until RT60 hits the target. Noise from next door needs transmission loss — mass and decoupling, the STC territory of the acoustic calculator. Soft foam on a party wall does approximately nothing for transmission; it treats the wrong mechanism.
OSHA says my workplace passes but NIOSH says it does not. Which is right?
Both, on their own terms. OSHA is the legal minimum (90 dBA PEL, 5 dB exchange rate); NIOSH is the health-protective recommendation (85 dBA, 3 dB exchange), and the 3 dB rate reflects how acoustic energy actually accumulates. The noise exposure tool computes both doses from the same shift so you see the gap. Compliance means OSHA; hearing conservation programs increasingly follow NIOSH.
Will a fence stop the road noise reaching my yard?
Only if it breaks line of sight between source and receiver — that is the first check in the noise barrier tool. Beyond that, insertion loss follows Maekawa's Fresnel-number curve: practical barriers deliver roughly 5–15 dB, with height past bare line-of-sight blocking paying off steeply at first and then flattening. Gaps ruin everything; a barrier with a hole performs like the hole.