Every room has its own sound

The ABC of the acoustic fundamentals does not always have to be so complicated. Here are some basic facts and explanations why acoustics should not be neglected in today’s spatial planning.

An atmosphere that is perceived as pleasant in terms of acoustics and optics increases productivity and well-being. In order to achieve an adequate room acoustic effect, there are a number of factors that need to be considered in the planning and design process.

  • field of activity
  • Room size
  • Furnishing
  • Surface covering of the room elements
  • Average number of persons
  • Due to this: the reflection and sound absorption of surfaces arising in the room

In addition, loudness and noise are perceived subjectively and are not entirely insignificant for the assessment and evaluation of room acoustic measures. For example, usual noises are perceived as less disturbing than new or changing noises. Starting with a slight increase in noise level, stress reactions and concentration problems can occur that can lead to both short-term and long-term health risks.

There are now numerous standards for the acoustic evaluation and calculation of rooms and sound-absorbing elements. The central task in room acoustics is to ensure speech communication and the associated optimization of the reverberation time in order to ensure health-preserving acoustics.

We are pleased to assist you with the acoustical measurement of your premises and advise you on the best possible execution methods in order to create a pleasant atmosphere in your environment.

If you have further questions or suggestions, please do not hesitate to contact us by phone or via the  contact form.

In the following, you will find some explanations of the most important room acoustics principles and parameters that must be taken into account in order to achieve optimum results.

Equivalent sound absorption area

The equivalent sound absorption area is determined from the ideal (assumed) area that completely absorbs, α = 1.

It can be determined for any objects, surfaces and even persons and is therefore essential for the characterization of room acoustics. It is also necessary for the calculation of the reverberation time.

A = α * s (m²)

s = associated geometric surface

α = coefficient; Sound absorption of the absorber

Thus, it should be excluded that α> 1


The frequency in general represents the repetition of a sound event over a certain period of time (measured in seconds). In room acoustics, the focus is mainly on the frequency range between 100 Hz and 5000 Hz. The human speech range is between 250 Hz and 2000 Hz. A high frequency is perceived as a high tone, a low frequency as a low tone. The frequency is important in that both the reverberation time and the degree of sound absorption are dependent on the frequency. Using the frequency counter, the various values ​​are relatively easy to measure and rooms and sound absorbers can be adjusted accordingly.

The Lombard – Effect

In the so-called Lombard effect, a speech sound of one person / group becomes a disruptive factor for another. The loss of speech intelligibility is compensated for by an increase in voice and volume, which in turn means that the mutual interference only continues to increase. This unwanted side effect can lead to physical and mental stress. Disability and illness are the result. To counteract this acoustically adapted premises are ideal.

Reverberation time

The reverberation time is a measure of the acoustic quality or evaluation and design of rooms. Depending on the function (usage) of the room, a shorter or longer reverberation time is an advantage.

The reverberation time is the time in which a sound is reduced by 60 dB of its initial value after switching off the sound source in a room. It should be noted that the larger a space and the higher the reflection of the surface materials, the longer the reverberation time. Conversely, this means that the more sound-absorbing surfaces or the higher the sound absorption of a material in the room, the lower the reverberation time.

(Prerequisite diffuse sound field). Calculable from the reverberation formula according to Sabine (1898) (Depending on the volume of space, available furnishings and their surface covering)

Reverberation time T = 0.163 * V / A (s)

V = volume of space (m3)

A = equivalent absorption area (m2)

0.163 = determined by Sabine

Sound absorbers

Sound absorbers are characterized by the property of materials from incident sound into other forms of energy, e.g. convert heat energy, thus dampen sound. Even a classified as weak absorber fulfills its effectiveness when z. B. its area is larger. Sound absorbers must always be considered frequency-dependent.

Sound absorption coefficient α

An important parameter for measuring sound-absorbing properties of materials is the sound absorption coefficient α. This measures the ratio of absorbing to impacting sound. The value lies between α = 0 and α = 1, where 0 means a complete reflection and 1 a complete absorption. Singular values ​​of the frequency-dependent α (s) are determined by means of measuring methods in the reverberation room according to DIN EN ISO 354.

For objects for which the sound-absorbing surface cannot be determined, the equivalent sound absorption surface is given.

At α = 0.3, 30% of the sound energy is absorbed and converted into other forms of energy and 70% reflected.

Sound absorption coefficient α = 0

Complete reflection of the sound, no sound absorption.

Sound insulation

The sound insulation is defined by the acoustic separation of rooms from each other or to the outside. The propagation of sound is reduced or prevented (by room limitations).

Sound absorption

The sound absorption changes the surround sound within a room and contributes to the improvement of the room acoustics. Material may vary – transform into other forms of energy.