The science of sound can be a complex topic. As an introduction, here are simple explanations of terms and concepts involved in the evaluation and management of acoustics in the built environment.

Sound absorption icon. Arrow representing sound is absorbed in to a panel.

The opposite of reflection. When a sound wave encounters resistance, absorption occurs which is measured in sabins.

Acoustic icon depicting a sound wave within a space.

The properties or qualities of a room or building that determine how sound is transmitted within it.

Ambient noise icon depicting sound bouncing around a space

The pervasive background noise, with the exclusion of the primary sound (i.e. a speaker's voice) within a given environment. Sometimes referred to as noise pollution.

Acoustic ceiling cloud icon

An acoustic element suspended from the ceiling or roof structure for sound absorption.

decibel icon (dB)

A unit that measures the intensity of a sound wave. A whisper is typically around 15 dB and a hammer hitting a nail is about 125 dB – enough to cause hearing damage.

Diffusion icon: arrows representing sound bounce of panels in random directions.

The random distribution or scattering of a sound wave after contacting a surface. Effective diffusion results in a well-balanced acoustic environment.

Echo icon depicting sound waves bouncing back

A distinctly discernible repetition or reflection of a sound.

Loudness icon: Curves progressivley increasing in size

Subjective impression of the intensity of a sound.

Noise icon: jagged curves represnting undesireable sound.

An unwanted sound, especially one that is loud or unpleasant or that causes disturbance.

Noise Reduction Coefficient icon: An arrow represnting sound is partially absorbed into a pane. Along the panel is are evenly spaced lines indicating measurement.

The numeric representation of sound absorption. The NRC scale ranges from 0, the measure of perfect reflection, to 1, indicating perfect absorption.

Reflection icon: an arrow representing sound deflects of a panel.

The bouncing of a sound wave off of a surface. Sound, like light, is reflected with an angle of reflection equaling the angle of incidence.

Reverberation icon: Original sound represented as a large arrow is surrounded by smaller arrows representing numerous reflecting of the original sound.

The persistence of sound in space after the originating sound has stopped. Reverberation is caused by numerous reflections of a sound arriving at the listener's ear so closely that they are heard as a gradual deterioration of sound quality.

Reverberation icon: Original sound represented as a large arrow is surrounded by smaller arrows representing numerous reflecting of the original sound. A clock graphic represents the measure of time.

The amount of time (seconds) required for a sound at a specific frequency to decay is 60 dB after the source stops. A room's reverberation time is impacted by frequency, the volume of the space, and the total number of absorption units in the room.

Sabin icon: An arrow depicting sound absorbs into a panel.

The unit of measure that indicates the sound absorption of a surface. One sabin is equal to one square foot of perfectly absorptive material.

Sound icon: a graphic depiction of a sound wave as a line interval graphic with vertical lines of various lengths creating peaks and valleys.

Energy transmitted by pressure waves in air, water, or solids. This form of energy is the cause behind hearing.

The number rating system that indicates the sound transmission loss of a wall or partition. STC is used to compare the sound transmission characteristics of architectural materials and construction methods.