Articles tagged “octave band”
9 articles covering octave band in acoustic engineering and building design.
What is a Background Noise Survey?
A background noise survey measures ambient noise levels in octave bands to assess compliance with NC, NR, or RC criteria. Learn methodology, equipment, standards, and how results affect acoustic design.
What is an NC Rating?
NC (Noise Criteria) is an octave-band rating system for background noise in buildings. Learn how NC curves work, how to read them, target values by room type, and how NC relates to NR and RC.
What is an NR Rating?
NR (Noise Rating) is the European octave-band system for specifying acceptable background noise in buildings. Learn how NR curves work, how they compare to NC, and NR targets by room type.
Ceiling Absorption Calculation: Octave-Band RT60 Prediction for 3 Ceiling Types
Same 200 m³ room, three ceiling systems: 15mm mineral fibre, 25mm perforated metal with backing, and 50mm exposed mineral wool. Full Sabine RT60 for each at 125–4000 Hz.
NC Curve Calculation from Octave-Band Measurements — Step-by-Step
Determine the NC rating from a set of octave-band background noise measurements. Step-by-step tangent curve method, controlling frequency identification, and RC Mark II comparison.
Free NRC Comparison Cheat Sheet — 50 Products with Octave-Band Data (PDF)
NRC comparison table for 50 acoustic products with full octave-band absorption data (125–4000 Hz). Ceiling tiles, wall panels, flooring, and furniture with real absorption coefficients.
The 125Hz Problem Nobody Treats — Why Your Meeting Room Still Sounds Like a Cave
Meeting rooms pass RT60 tests at 500Hz and still sound terrible. The culprit is 125Hz bass reverberation — standard acoustic foam panels have α ≈ 0.05 at 125Hz and do almost nothing. Here is the calculation that reveals the problem and the bass trap specification that solves it.
Understanding Octave Band Analysis: Why Single-Number Ratings Hide the Truth About Your Room
A single RT60 value or NRC rating averages across frequencies and hides critical problems. Octave band analysis breaks sound into 6 frequency ranges — revealing that your room might pass at 500Hz and catastrophically fail at 125Hz. Here is how octave bands work and why every acoustic assessment should use them.
NRC 0.75 Does Not Mean 75% Absorption — Here Is What It Actually Means
NRC is an arithmetic average of four octave bands. A panel rated NRC 0.75 can have α = 0.40 at 250Hz — and that bass deficiency will make your meeting room fail its WELL F74 assessment at the exact frequency where speech intelligibility lives.