Wavelength
Means the distance between the two peaks of a sound wave. The wavelength of audible sounds is about 20mm - 20 m.
Absorbent
The substance into which sound is absorbed.
Absorboida
To suck in, to bind. For example, an acoustic material absorbs sound to muffle it.
Absorption
Sound absorption in the substance.
Absorption area
Knowing the absorption area and the volume of the room, the approximate value of the reverberation time can be calculated. For a piece or surface absorption area is calculated as the surface area times the absorption coefficient.
Absorption coefficient, absorption ratio
The ability of a material to absorb sound. The absorption coefficient can be used to calculate reverberation times. A material that absorbs sound well has an absorption coefficient greater than 0.8.
Absorption class
Sound-absorbing panels or boards are classified in absorption classes A-E according to EN ISO 11654. Attenuation is measured at frequencies between 200 and 5000 Hz.
Acoustics
A branch of physics that studies sound. The science of sound covers all the physical phenomena that humans perceive through their sense of hearing.
Amplitude
Peak sound pressure in a sound wave.
Articulation index (AI)
An acoustic indicator of speech intelligibility.
Articulation class (AC)
Acoustic privacy between workstations in open plan offices is expressed in terms of articulation class (AC). The higher the AC value, the better the privacy achieved in the open-plan environment. Good privacy requires a minimum AC value of 180.
Desibeli
A unit of sound pressure level.
Reflection
The change in direction of a sound wave or wavefront as it reaches an interface.
Porous dampers
Examples of porous absorbers include products made of mineral wool, foam and fabrics. A porous absorber has a surface through which sound waves pass.
Room acoustics
Sound behaviour in a room. A key measure of room acoustics is the reverberation time, which describes the echo in a room.
Reverberation time
Reverberation time is a unit of measurement of reverberation and the effectiveness of sound attenuation. The reverberation time is the time it takes for the sound pressure level to drop to 60 dB.
Noise
Unwelcome, disturbing sound. A subjective concept.
Speech intelligibility
Speech intelligibility depends on the background noise level, the reverberation time of the room and the shape of the room.
Speech Transfer Index (STI)
The speech intelligibility index is a measure of the intelligibility of the speech transmitted. It is generally applicable to measure the impact of different acoustic environments, transmission channels and interference.
Building acoustics
Sound behaviour in buildings. Building acoustics is often concerned with the transfer of sound from one space to another, i.e. sound insulation.
Resonance
This is caused by sound being reflected between two opposing walls. Resonances occur in the length, width and height of the room, i.e. between the end walls, between the side walls and between the floor and the ceiling.
Hall acoustics
Acoustics of large spaces such as concert halls
Frequency or frequency
A unit of vibration, and therefore of sound frequency, indicating the number of vibrations per second. The unit of frequency is the hertz (Hz). The higher the number, the higher the pitch, and the lower the number, the lower the pitch (treble - bass). The human ear hears sounds with frequencies in the range 20 to 20,000 Hz. The frequency of a speech sound is between 125 and 8000 Hz.
Background noise
A disturbing, non-informative sound, for example from air conditioning equipment in a room. High background noise levels can cause adverse long-term effects such as fatigue, nausea and reduced efficiency and productivity.
Asterisk
Rapidly repeating echo sound. Occurs when a sound wave propagates between opposing walls.
Soundproofing
The ability of a structure to prevent sound from passing from one state to another or through the structure.
Sound pressure
The variation in air pressure created by sound waves is called sound pressure (Lp). The unit of sound pressure level is the decibel (dB). The lowest sound pressure level we can detect is the threshold of hearing (0 dB). Loud sounds exceed the pain threshold and cause pain (around 120 dB).
Sound attenuation or sound absorption
Sound absorption refers to the conversion of sound energy into another form of energy (usually heat) as sound travels through a medium. Sound absorbers are materials and structures that have the ability to convert the kinetic energy of sound waves into another form of energy. They improve the acoustics of a room by eliminating the reflections of sound waves. The noise level is reduced and the reverberation time is shortened.
Sound attenuation class
Sound absorption panels are classified in absorption classes A-E according to EN ISO 11654. The measurement is carried out at frequencies between 200 and 5000 Hz. Class A products have the best attenuation performance.
Volume (Lp)
A synonym for sound pressure level. The unit is the decibel (dB). Measured at different sound frequencies.
Sound
A vibration propagating in the medium, which causes an auditory perception.
Sources:
https://www.ecophon.com/fi/akustiikkaratkaisut/akustiikan_tietopankki/
https://www.kotiakustiikka.fi/huoneakustiikka.html
https://fi.wikipedia.org/wiki/%C3%84%C3%A4ni
http://www.cs.tut.fi/sgn/arg/akusem/akuintro.pdf
http://www2.siba.fi/akustiikka/index.php?id=8&la=fi
Kylliäinen, M. and Hongisto, V. (2007). Acoustic design of buildings. Helsinki: Finnish Association of Civil Engineers.
Kylliäinen, M. and Hongisto, V. (2011). Acoustic design of buildings: industrial premises. Helsinki: Finnish Association of Civil Engineers.
