Acoustic knowledge

Improve room acoustics

In work and meeting rooms, room acoustics have a major impact on the productivity and well-being of users. Noise and unwanted sounds are distractions that cause stress and can seriously affect employee performance.

We at Lindner are interior design and room acoustics specialists with over 50 years of experience in the development of acoustically optimised room concepts.

Acoustics and sound insulation have proven to be one of the most important quality factors
for new construction and renovation projects worldwide. And for good reason, because loud and reverberant rooms are unpleasant and make it more difficult to concentrate.


The requirements are very different and for each project,
depending on, for example, the type of use, the shape of the building and the type of construction, must be considered separately.

MUTE+® sound absorbers are ideal for optimising your room acoustics.
We would be happy to develop project-specific solutions together with you; for this purpose, we can draw on a wide range of acoustic test certificates.

Room acoustics glossary

Room acoustics

Room acoustics deals with the propagation of sound within a room. In order to create an acoustically appropriate space, the size of the room and the appropriate arrangement of sound-absorbing measures are important, as is the subsequent use of the room. For example, in classrooms, good speech intelligibility and in concert halls, a spatial music experience are important.
The most important factor in the acoustic design of rooms is sound absorption.
Various room acoustic parameters play a decisive role.

Sound absorption coefficient α

The sound absorption coefficient α describes the ratio of incident to non-reflected sound per frequency. The absorption is tested using a standardized procedure and given as a single number for the rated sound absorption coefficient αw.

For complete reflection a = 0
and for complete absorption a = 1.

Sound absorption classes

The evaluated sound absorption coefficients αw are determined according to DIN EN ISO 11654 in different sound absorption classes:

A = ≥ 0.90 highly absorbent

B = 0.80 to 0.85 highly absorbent

C = 0.60 to 0.75 highly absorbent

D = 0.30 to 0.55 absorbent

E = 0.15 to 0.25 slightly absorbent

not classified ≤ 0.1 reflective

Rated sound absorption coefficient αw

The weighted sound absorption coefficient αw according to DIN EN ISO 11654 is determined for five octaves with the center frequencies 250 to 4,000 Hz. For this purpose, a predetermined weighting curve in steps of 0.05 so that the sum of the most unfavourable deviations ≤ 0.10. The value reached at the frequency 500 Hz corresponds to the value of αw.

Practical sound absorption coefficient αp

The practical sound absorption coefficient αp is specified with six values at 125 Hz, 250 Hz, 500 Hz, 1,000 Hz, 2,000 Hz and 4,000 Hz. Each value is determined from three centre values. These are added together, averaged and then rounded up or down in steps of 0.05.

Example:
200 Hz: 0.65
250 Hz: 0.72
315 Hz: 0.86

The practical sound absorption coefficient αp at 250 Hz corresponds to 0.75.

Equivalent sound absorption area

The equivalent sound absorption area is defined as the product of the sound absorption coefficient and its area. 10 m² of ceiling area with a sound absorption coefficient of 0.50 has an equivalent sound absorption area of ​​5 m². A ceiling area of ​​20 m² and a sound absorption coefficient of 0.25 therefore has the same effect in the room.
Canopy ceilings are individual objects that are exposed to sound all around. Unlike flat components, these are tested as freely distributed individual elements in the reverberation room. The sound absorption capacity of canopy ceilings is therefore specified as the equivalent sound absorption area per canopy [m²] in a defined dimension.

Reverberation time

Reverberation time is the time interval in seconds within which the sound pressure in the room drops by 60 dB. The optimal reverberation time depends on the purpose of a room.

Recording studio < 0.3 s
Classroom 0.6 to 0.8 s
Concert hall 1.5 to 3 s

Frequency

The frequency is the number of oscillations per second – the unit is Hertz [Hz].
The frequency characterises the pitch.
Listening/Music 20 to 20,000 Hz
Speaking/singing 200 to 2,000 Hz
Room acoustics 100 to 5,000 Hz

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