Common Acoustic Terms

Absorption

The process where sound energy is soaked up by a surface rather than reflected back. Soft and porous materials like fabric, foam, and PET felt are good absorbers.

Absorption Class

A European rating system (Class A to E) showing how effective a material is at absorbing sound. Class A is the most effective, typically used in acoustic panels.

Acoustic Baffles

Vertical sound-absorbing panels that hang from the ceiling. They reduce echo and reverberation in large, open spaces such as offices, schools, or halls.

Acoustic Ceiling Rafts

Flat, suspended panels that hang horizontally below the ceiling. They absorb sound while maintaining an open, modern aesthetic.

Background Noise

The ambient sound in a space, created by things like HVAC systems, outside traffic, or chatter. Managing background noise is essential for comfort and focus.

Decibel (dB)

The unit used to measure sound levels. A whisper is around 30 dB, normal conversation is about 60 dB, and a rock concert can reach 120 dB.

Diffusion

The scattering of sound waves in many directions, reducing harsh echoes without removing sound energy. Diffusers are often used in music studios and performance spaces.

Echo

A distinct, repeated sound caused when sound waves bounce off a hard surface and return to the listener with a noticeable delay.

Flutter Echo

A rapid, buzzing-like echo that occurs when sound bounces repeatedly between two parallel hard surfaces, such as bare walls in a corridor.

Frequency

The pitch of a sound, measured in Hertz (Hz). Low frequencies are bass sounds (like thunder), while high frequencies are treble sounds (like birdsong).

Impact Noise

Noise created by physical contact with a surface — for example, footsteps on a hard floor or chairs scraping. Unlike airborne noise, it travels through structures.

Noise Reduction Coefficient (NRC)

A rating (from 0.0 to 1.0) that shows how much sound a material absorbs. An NRC of 0.80 means the surface absorbs 80% of sound energy and reflects 20%.

Reverberation

The persistence of sound in a room after the source stops. Caused by reflections from surfaces like walls and ceilings. High reverberation makes speech harder to understand.

Reverberation Time (RT60)

The time it takes for sound to decay by 60 dB. Offices aim for around 0.5 seconds; churches may have over 2 seconds for music.

Room Acoustics

The overall sound environment in a room, shaped by its size, surfaces, and contents. Good room acoustics balance clarity with comfort.

Sabin

The unit of sound absorption. One sabin equals the absorption of one square foot of perfectly absorptive material.

Sound Absorber

Any material or product that reduces reflections by absorbing sound waves, such as acoustic panels, curtains, or carpets.

Sound Absorption Coefficient (α)

A number between 0 and 1 that shows how well a material absorbs sound at specific frequencies.

Sound Insulation (Soundproofing)

Building methods or materials that block sound from travelling between spaces. Different from sound absorption, which improves sound within a space.

Sound Masking

A technology that introduces low-level background sound to cover up speech and reduce distractions in open-plan offices.

Speech Privacy

The ability to prevent conversations being overheard by unintended listeners. Achieved through sound masking, absorption, or partitioning.

STC (Sound Transmission Class)

A US rating system showing how well a wall, door, or partition blocks airborne sound. Higher STC means better sound isolation.

White Noise

A sound containing all frequencies at equal intensity, often used in simple noise machines. Modern sound masking uses a more comfortable, speech-shaped spectrum.

Zoning

The division of a building into different acoustic or sound masking areas, allowing separate control of noise levels and privacy.