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home >  News >  Glossary of acoustics

A

Abbreviations  – Important abbreviations in the field of acoustics

Acoustics  – Interdisciplinary science of sound and mechanical oscillations covering diverse subjects such as room and voice acoustics.

Airborne sound  – Sound propagated as waves in the air. Airborne sound waves are generally spherical.

E

Equivalent sound absorption area  – The theoretical area of a room with a sound absorption coefficient of 1 and achieving the same absorption as the entire surface of the room under consideration, including the objects contained in it.

F

Frequency f  – The number of oscillations per second. Frequency (symbol: f) determines pitch and is specified in Hertz (Hz). The human ear is generally able to perceive frequencies ranging from 20 to 16,000 Hz.

I

Inverse square law  – The reduction in the sound pressure of spherical waves in an emitter's far field is 6 dB each time the distance doubles, not considering air absorption.

R

Rating level  – A value which is averaged and corrected over a particular period of time. It is used primarily for comparison with emission levels.

Reverberation time  – Reverberation time is the most important measurement variable in room acoustics. It is defined as the time taken by sound energy inside a room to drop by 60 dB after deactivation of the sound emitter.

S

Sound  – Sound can be thought of as mechanical oscillations in an elastic medium. Sound impinging on a molecule causes it to vibrate about its rest position.

Sound absorption  – Conversion of sound energy into heat. Porous sound absorbing materials are used mainly to absorb airborne sound; in this process, the air molecules' kinetic energy (sound energy) is converted into heat through friction with the pores of the sound absorber.

Sound insulation  – Blockage of sound transmission by means of a partitioning surface.

Sound pressure level Lp  – The sound pressure level Lp is the logarithmic sound pressure p specified in decibels (dB) with respect to the sound pressure po (hearing threshold).

Sound pressure p  – Vibrating molecules cause pressure fluctuations in the surrounding medium, e.g. air, thus changing the air pressure correspondingly. These values can be measured and are expressed as sound pressure (symbol: p).

Speed of sound c  – The speed at which sound waves travel. The speed of sound (symbol: c) depends notably on the medium of propagation.

Standard emission values  – A number of regulations specify these values as maximum rating levels for neighborhoods and workplaces. These regulations include technical instructions on noise, VDI 2058 sheet 1, accident prevention regulations on noise and VBG 121 (implementation ordinance).

Structure-borne sound  – Sound propagated in solid media or on their surfaces.

W

Wavelength lambda  – The distance from any one point to the next point of a corresponding phase on a wave. The relationship between the speed of sound c, frequency f and wavelength lambda is: c = f x lambda