The Decor Systems Acoustics Glossary

The Decor Systems Acoustics Glossary

We've compiled the key terminology when it comes to all things acoustics. Bookmark this page for easy access to the information you need.

Absorption

In relation to acoustics, absorption refers to the process by which a material or surface absorbs sound waves, rather than reflecting them. Absorption is a key factor in controlling the acoustics of a space, as it helps to reduce the reverberation time, which is the amount of time it takes for the sound to decay after the sound source has stopped. Absorption is particularly important in spaces such as auditoriums and theatres, where the ability to hear and understand speech is crucial. Absorption can be achieved through the use of materials such as acoustic panels, sound-absorbing ceiling tiles, and carpeting.

Absorption Coefficient (alpha)

The dimensionless ratio of absorbed to incident sound energy from a single interaction between a sound wave and a partition. Values range from 0 to 1.

Acoustic Impedance

A measure of how hard it is for sound to pass through a material.

Acoustic Material Selection

The careful choice of materials in a space to control acoustics. Soft furnishings typically diminish reflections and reduce the reverberation time, while hard surfaces like concrete, glazing, and plasterboard tend to increase reverberation time. The selection of complementary acoustic panel systems is crucial to ensure adequate acoustic control.

Acoustics

Acoustics is the study of sound and its properties, including how sound is produced, transmitted, and received. It encompasses the physical properties of sound, such as frequency, wavelength, and amplitude, as well as the behaviour of sound in different environments, such as how it reflects, refracts, and absorbs. Acoustics also includes the study of how sound is perceived by the human ear and how it can be measured and controlled. The field of acoustics is used in various applications, including architectural design, audio engineering, speech therapy, noise and vibration control, and more.

Ambient Noise

All-pervasive noise associated with a given environment.

Attenuation

The reduction of sound energy as a function of distance travelled.

Ceiling Attenuation Class (CAC)

CAC refers to the Ceiling Attenuation Class (CAC) value, which is a rating that describes a material's ability to prevent sound from travelling between partitions through the ceiling cavity. It is usually required between private spaces when the walls do not go full height.

Damping

The loss of energy in a vibration system, usually through friction.

Decibel (dB)

A unit of sound level that implies 10 multiplied by a logarithmic ratio of power or some quantity proportional to power. Sound intensity is described in decibels.

Diffusion

The scattering or random distribution of a sound wave after striking a surface.

Echo

The repeating of sound caused by the reflection of sound waves.

Flutter

A repetitive echo set up by parallel reflecting surfaces.

Frequency (f)

The number of oscillations or cycles per unit of time. Acoustical frequency is usually expressed in Hertz (Hz). Humans can hear sounds with frequencies between 20 and 20,000 Hz.

Hertz (Hz)

The frequency of sound expressed by cycles per second.

Isolation

Resistance to the transmission of sound by materials and structures. The separation of airborne or mechanically transmitted energy.

Noise

Any unwanted sound that has the potential to cause a perceived disturbance.

Noise Isolation

The reduction of sound transmission between adjacent rooms or spaces.

Noise Reduction Coefficient (NRC)

A rating that indicates the average sound absorption of a material across a range of frequencies. An NRC of 1.0 indicates that the material absorbs all sound, while an NRC of 0.0 indicates that it absorbs no sound.

Pitch

The perceived auditory sensation of sounds expressed in terms of the high or low-frequency stimulus of the sound.

Reflection

The portion of a sound wave that is not absorbed when meeting an object. It changes direction and continues to travel. It is the opposite of absorption.

Reverberation

Refers to the time (in seconds) taken for the sound pressure level generated by a source to decay by 60 decibels following the conclusion of the source event. It provides relevant information for assessing speech intelligibility and the acoustic quality of a space.

Reverberation Time

The time (in seconds) taken for the sound pressure level generated by a source to decay by 60 decibels following the conclusion of the source event. It provides relevant information for assessing speech intelligibility and the acoustic quality of a space. Sometimes referred to as the "echo" in a room.

Rw

Refers to the weighted noise reduction that roughly corresponds to the decibel scale. It is a measure of how much airborne sound is attenuated between a partition. This is the descriptor that would usually be described as "Soundproofing."

Sound Absorption

The ability of a material or surface to reduce sound reflection and reverberation. It is typically measured in units such as Noise Reduction Coefficient (NRC) or Sound Absorption Coefficient (SAC).

Sound Absorption Coefficient (SAC)

The fraction of energy striking a material or object that is not reflected.

Sound Field

The sound that exists in a room, space, or outdoor environment.

Sound Insulation

The reduction of the transmission of sound through walls, floors, and ceilings.

Sound Pressure Level (SPL)

A measurement of the amount of acoustic energy in a sound, measured in decibels (dB).

Sound Transmission

The ability of a material or surface to block or transmit sound. It is typically measured in units such as Sound Transmission Class (STC) or Impact Insulation Class (IIC).

Standing Wave

The resonant vibration of a sound wave in a closed space, caused by reflections from walls, floors, and ceilings.