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.
Absorption
The opposite of reflection. When a sound wave encounters resistance, absorption occurs which is measured in sabins.
Acoustics
The properties or qualities of a room or building that determine how sound is transmitted within it.
Ambient noise
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.
Ceiling Cloud
An acoustic element suspended from the ceiling or roof structure for sound absorption.
Decibel
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
The random distribution or scattering of a sound wave after contacting a surface. Effective diffusion results in a well-balanced acoustic environment.
Echo
A distinctly discernible repetition or reflection of a sound.
Loudness
Subjective impression of the intensity of a sound.
Noise
An unwanted sound, especially one that is loud or unpleasant or that causes disturbance.
Noise Reduction Coefficient (NRC)
The numeric representation of sound absorption. The NRC scale ranges from 0, the measure of perfect reflection, to 1, indicating perfect absorption.
Reflection
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
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 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
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
Energy transmitted by pressure waves in air, water, or solids. This form of energy is the cause behind hearing.
Sound Transmission Class (STC)