Acoustic Glossary

Acoustic Glossary

Here you will find the home to our acoustic glossary. We know that the terminology used in acoustics can be confusing, especially as many terms are quite similar. You will find terms that are commonly found in acoustic reports, and product specifications (i.e. acoustic panels, sound level meters, etc).

Acoustic Terms

Band of frequencies in which the upper limit of the band is twice the frequency of the lower limit.

[BS 8233:2014]

Band of frequencies in which the upper limit of the band is 2 1/3 times the frequency of the lower limit.

[BS 8233:2014]

When sound waves encounter a soft or porous material surface (e.g. acoustic panels or foam), they lose energy (in the form of heat) that would otherwise be reflected.

When elements of a structure vibrate they radiate noise and, if the vibration is high enough, this noise can be audible. Groundborne and structure-borne noise are rarely an issue outside buildings or structures.

[BS 8233:2014]

Average sound pressure level in a specific frequency band in a room below a floor when it is excited by a standard tapping machine or equivalent.

[Bs 8233:2014]

Impact sound pressure level normalized for a standard absorption area in the receiving room.

[BS 8233:2014]

A-weighted sound pressure level obtained using time-weighting “F”, which is exceeded for N% of a specified time interval.

Example: LA90,1hr is the A-weighted level exceeded for 90% of 1hr.

[BS 8233:2014]

Time that would be required for the sound pressure level to decreased by 60dB after the sound source has stopped.

Note: Reverberation time is usually measured in octave or third octave bands. It is not necessary to measure the decay over the full 60dB range. The decay measured over the range 5dB to 35dB below the initial level is denoted by T30, and over the range 5dB to 25dB below the initial level by T20.

[BS 8233:2014]

Impact sound pressure level normalized to a reverberation time in the receiving room of 0.5s.

[BS 8233:2014]

Quantity of sound pressure, in decibels (dB), given by the formula:

Lp = 10log(p/p0)^2

Where:

P is the root-mean-square sound pressure in pascals (Pa);

P0 is the reference sound pressure (20 micro-pascals)

Note: The range of sound pressures for ordinary sounds is very wide. The use of decibels gives a smaller, more convenient range of numbers. For examples, sound pressure levels ranging from 40dB to 94dB correspond to sound pressures ranging from 0.002 Pa to 1 Pa. A doubling of sound energy corresponds to an increase in level of 3dB.

[BS8233:2014]

A device that is used to measure sound pressure levels. It is usually a handheld, electronic device, attached to a microphone and pre-amp.

Modern devices are able to provide detailed analysis of sound through filters.

Laboratory measure of the sound insulating properties of a material or building element in a stated frequency band.

[BS 8233:2014]

Sound power or acoustic power is the rate at which sound energy is emitted, reflected, transmitted or received, per unit time.[1] The SI unit of sound power is the watt (W).[1] It is the power of the sound force on a surface of the medium of propagation of the sound wave. For a sound source, unlike sound pressure, sound power is neither room-dependent nor distance-dependent. Sound pressure is a property of the field at a point in space, while sound power is a property of a sound source, equal to the total power emitted by that source in all directions.

[Wiki – https://en.wikipedia.org/wiki/Sound_power]

Difference in sound level between a pair of rooms, in a stated frequency band, normalized to a reference reverberation time of 0.5s for dwellings.

[BS8233:2014]

Single-number quantity that characterizes airborne sound insulation between rooms, but which is not adjusted to reference conditions.

[BS 8233:2014]

Single-number quantity used to characterize the impact sound insulation of floors over a range of frequencies.

[BS 8233:2014]

Single-number quantity which characterizes the airborne sound insulating properties of a material or building element over a range of frequencies.

[BS 8233:2014]

Single-number quantity that characterizes the airborne sound insulation between rooms.

[BS 8233:2014]

Single-number quantity used to characterize the impact sound insulation of floors over a range of frequencies.

[BS 8233;2014]