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.
The opposite of reflection. When a sound wave encounters resistance, absorption occurs which is measured in sabins.
The properties or qualities of a room or building that determine how sound is transmitted within it.
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.
An acoustic element suspended from the ceiling or roof structure for sound absorption.
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.
The random distribution or scattering of a sound wave after contacting a surface. Effective diffusion results in a well-balanced acoustic environment.
A distinctly discernible repetition or reflection of a sound.
Subjective impression of the intensity of a sound.
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.
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.
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.
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.
The unit of measure that indicates the sound absorption of a surface. One sabin is equal to one square foot of perfectly absorptive material.
Energy transmitted by pressure waves in air, water, or solids. This form of energy is the cause behind hearing.
Sound Transmission Class (STC)