How much sound energy a material converts to heat rather than reflecting it. Reported as a coefficient between 0 and 1 by frequency band. Porous materials (e.g., mineral wool, fabric panels) increase absorption and reduce reverberation.

Imaging system that overlays a “sound map” onto video, helping locate dominant noise sources on-site for fast troubleshooting and verification.

Sound that travels through air (speech, music, traffic) as opposed to structure‑borne sound transmitted through building elements.

Ambient sound level from all sources other than the one of interest. Important for offices, hotels, and measurements (affects dynamic range and audibility).

Structure placed between source and receiver to block line‑of‑sight and reduce sound via diffraction and attenuation. Performance depends on height, length, material, and distance.

Frequency weighting with less roll‑off at low frequencies than A‑weighting; useful for measuring bass or industrial low‑frequency noise.

Logarithmic unit for ratios of sound pressure or power. A 10 dB increase is perceived as roughly twice as loud; +3 dB ≈ doubling of acoustic energy.

Single‑number ratings for airborne sound insulation of building partitions (walls, floors, doors). ASTM E413 defines STC. R_w (ISO) is the lab measure; D_nT,w is an on‑site rating normalised to reverberation time. For international field methods, see ISO 16283.

Energy‑averaged sound level over a period; the most common descriptor for varying noise.

Unwanted sound transmission via indirect paths (e.g., through ceilings, floors, façade, or structure) that bypass the main separating element.

Analysis that displays a continuous spectrum (fine frequency resolution) instead of octave bands; useful for tonal diagnostics.

Number of pressure cycles per second; relates to pitch. Human hearing spans ~20 Hz to 20 kHz.

Devices such as earmuffs or earplugs used to reduce exposure. Select using SNR/NRR with fit‑testing where possible.

Noise from footsteps or impacts transmitted through floors/structures. L_n,w is the standard on‑site impact noise rating; lower numbers are better.

Short, high‑level sounds with very fast rise time (e.g., hammer blows). Can require special metrics or peak detectors.

Community noise indicators. L_den applies penalties for evening/night periods to reflect increased annoyance. See WHO Environmental Noise Guidelines for health-based limits.

Statistical levels exceeded x% of the time. L₉₀ approximates background noise; L₁₀ represents higher events.

Room noise criteria used to judge HVAC/background noise acceptability. NC (ANSI) and NR (ISO) curves guide target spectra for comfort.

Single‑number absorption rating (0–1) averaging 250–2000 Hz. Higher NRC indicates more absorption. See ASTM C423 for test details.

Standard frequency bands for measurements and design. 1⁄3‑octave gives finer resolution to identify tones and match treatment to problems.

L_w is the source’s acoustic emission (independent of distance/room); SPL is what you measure at a position and depends on distance and acoustics.

Time for sound to decay by 60 dB after the source stops. Key for speech clarity and comfort. Measured following ISO 3382.

Classic relation linking room volume and total absorption to estimate RT60 at mid frequencies. Useful for early sizing of treatment.

Difference between the desired signal and background noise. In offices, +10 dB SNR or better improves intelligibility for speech.

Vibration and sound traveling through building elements (e.g., from MEP, footsteps). Often mitigated by isolation mounts and resilient layers.

North‑American single‑number rating of airborne sound insulation measured in laboratory conditions. Higher is better. Defined in ASTM E413.

Frequency‑dependent reduction of sound through a partition. Forms the basis for single‑number ratings like R_w/STC.

Noise with strong, narrow‑band components (e.g., fan tones). Often needs additional penalties in regulations and specific mitigation.

Use of springs, elastomers, pads, or floating slabs to reduce structure‑borne transmission from equipment or footsteps.