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Flanking noise is sound that transmits between spaces indirectly going over or around. Flanking can result from both impact and airborne sounds. Typical elements which cause flanking might include; windows, doors, flanking ceilings/ doors and walls or penetrating joists.

Sound resulting from the impact between colliding bodies.

Sound or noise radiated directly from a source, such as a loudspeaker or machine, into the surrounding air.

Classification of sound absorbers into Sound Absorption Classes A-E, according to EN ISO 11654, including frequencies 200-5000 Hz.
Class A being the best rating, near 0% reflection.

The ability of a building element or building structure to reduce the sound transmission through it. The sound insulation is measured at different frequencies, normally 100-3150 Hz. Airborne sound insulation is expressed by a single value, Dn,f,w, Rw or R’w. Impact sound insulation is expressed by a single value Ln,w or L’ n,w .

Means that sound energy is converted into mechanical vibration energy and/or heat energy. Sound absorption is expressed as the sound absorption coefficient α or the sound absorption class (A-E) according to EN ISO 11654 or NRC/SAA according to ASTM C 423

Single value for sound absorption according to ASTM C 423, derived as the mean value of 4 frequencies in the range 250-2000 Hz.

Vibrations of air molecules that travel through air carrying energy with them. Sound waves can also travel through water and solids, but cannot travel in space where there are no molecules to vibrate. When sound travels through air, the molecules do not actually move to a new location, instead each set of molecules “bumps” the molecules next to it, progressively transferring motion to new sets of molecules.

The amount of time it takes for a sound level to decrease by 60 dB within an enclosure after the sound source has stopped.

A measure of frequency, abbreviated as Hz. The number of oscillations (back and forth movements) per second.

The number of times a vibrating object oscillates (moves back and forth) in one second. Fast movements produce high frequency sound (high pitch/tone), but slow movements mean the frequency (pitch/tone) is low.

Reflections or repetitions of sound waves. Echoes can be produced by shouting in empty room with solid finishes, (for example, rock, laminate and glass)

A unit of measure commonly used to describe the sounds around us (abbreviated as dB). It’s based on a logarithmic scale which means a sound that is 3 decibels higher has twice as much energy.

A measure of how loud sounds are or sound intensity (abbreviation for decibel).

Single figure rating used to describe the loss of sound energy on reflection at a surface.

Single number quantity used to characterise the impact sound insulation of floors over a range of frequencies. The figure indicates the amount of sound energy being transmitted between two adjacent rooms within a building when tested on-site.

An adaptation of the sound insulation performance curve of an element of structure, used as a correction factor that targets low frequency noise (in particular 100–315 Hz).

Single number quantity that characterizes the airborne sound insulating properties of a material or building element over a range of frequencies. The figure indicates the amount of sound energy being stopped by the element when tested in a laboratory.