Room acoustics

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optimal acoustics in Greek (amphi) theaters
Concert hall with modern room acoustics

The acoustics is a field of acoustics , which deals with the impact of the structural conditions of a room to be held in his sound events. The focus of room acoustics is the design of the perceptibility of sound events by users of concert halls, theaters, assembly halls, classrooms, television and radio studios, churches and other rooms in which acoustic performances are made accessible to many listeners (technical room acoustics). Room acoustics also play an increasing role in everyday rooms (schools, restaurants, shopping centers, open-plan offices, etc.) and are included in the planning.

The aim of the planning is to adapt a room as well as possible to its intended purpose and the existing communication scenario. The characteristics of human hearing , the particularities of speech perception as well as subjective listening habits ( psychoacoustics ) and musical aesthetics must be taken into account.

Room acoustic planning

Direct sound, early reflections, and reverberation

The acoustic impression of a room is determined by

The task of room acoustics is to influence these parameters through room design in such a way that the acoustic properties of the room fit as well as possible to its intended purpose.

The goals of room acoustic design can be:

  • As far as possible, no influence of the room in the case of recording studios: The room should have as little reflection as possible so that the recorded sound is only determined by direct sound and the acoustic character of the recording room has as little influence as possible on the recording.
  • As high as possible speech intelligibility in classrooms, lecture halls and theaters: The proportion of direct sound should be high and early reflections should come from the direction of the speaker with relatively little delay, in order to increase the speaker's volume and support the speaker's localization. The reverberation should also set in early, but should subside relatively quickly (reverberation time <1 second) so that it also increases the speaker's volume without reducing speech intelligibility.
  • A musical experience that is as spatial as possible in concert halls: The proportion of direct sound should be balanced compared to the reflections - large enough to still perceive the music clearly and transparently, but not too large so as not to diminish the spatial impression. The early reflections should have a high proportion of the overall sound and should be distributed as well as possible in terms of direction, so that the impression is as spatial as possible. The reverberation should be spatially well distributed, make a noticeable contribution to the overall sound and not be too short in order to envelop the listener as well as possible in the music (reverberation times 1.5 to 2 seconds).

Since the room acoustic properties are practically incompatible for different applications, it is hardly possible to create a universal room that combines good speech intelligibility and a good spatial music experience. If this is nevertheless required, either the room has to be redesigned depending on the application (e.g. by pulling up heavy curtains in the concert hall for speech or creating additional reflection surfaces in the lecture hall for music), or the rooms have to be provided with electroacoustic sound (e.g. by distributing loudspeakers in the lecture hall, which are controlled by appropriate effects devices and thus simulate wall reflections and reverberation).

Parameters

Acoustically treated room for demonstration of HIFI systems.

The best known parameter of room acoustics is the reverberation time . This is the time span in which the sound pressure level of a sound event has decreased by 60  dB , i.e. to a thousandth of the initial sound pressure . The reverberation time is generally determined in octave bands or in third octave bands. If only one reverberation time value is given, then it is the reverberation time at 1000  Hz or at 500 Hz.

When designing room acoustics in rooms with higher requirements, it is also necessary to consider speech intelligibility in addition to the reverberation time. Therefore, for example, offices are not qualified by a reverberation time that can be achieved. In these rooms, which also include corridors, counter halls, call centers, libraries and rooms in the healthcare sector, speech intelligibility is more important. The amount and arrangement of the sound-absorbing surfaces is therefore of the utmost importance for the listening experience and the acoustic environment. One possibility is to use acoustic ceiling sails . The acoustic quality of a room in terms of speech intelligibility is called audibility . There are standardized syllable intelligibility tests to determine audibility .

Especially for music performances, the optimization of the room acoustics is achieved not only by installing sound absorbers but also by attaching diffusers . These dissipate the sound field in such a way that better perception is possible without causing over-insulation. The use of electroacoustic reverberation extension systems is also an option.

Individual evidence

  1. ↑ EBS: dB calculator. Sengpielaudio Berlin, June 1, 2014, accessed on July 8, 2020 .
  2. ↑ Ulf-J. Werner: Sound insulation and room acoustics - manual for theory and practice , Springer Verlag, Berlin, 2009.
  3. ↑ Ivar Veit: On speech intelligibility and its measurement. HGA, 1966, accessed 2020 .

literature

  • Leo Leroy Beranek: Concert halls and opera houses. Music, acoustics, and architecture . Springer, New York et al. 2004, ISBN 0387955240
  • Heinrich Kuttruff: Acoustics. An introduction . Hirzel, Stuttgart and Leipzig 2004, ISBN 3-7776-1244-8
  • Jürgen Meyer: Church acoustics . Bochinsky, Frankfurt am Main 2003, ISBN 3-923639-41-4
  • Christian Nocke: Room acoustics in everyday life - hearing - planning - understanding . 2nd edition, Fraunhofer IRB Verlag, Stuttgart 2019, ISBN 978-3-8167-8967-3
  • Rudolf Skoda: The Leipzig Gewandhaus buildings. International comparison of concert buildings . Verlag Bauwesen, Berlin 2001, ISBN 3345007819
  • Hugh Tallant: Hints on architectural acoustics , in: The Brickbuilder , vol. XIX, from No. 5 (May 1910), pp. 111–228 ( digitized version )
  • Stefan Weinzierl: Beethoven's concert rooms. Room acoustics and symphonic performance practice on the threshold of modern concerts . Bochinsky, Frankfurt am Main 2001, ISBN 978-3-923639-42-7

Web links

Commons : Room acoustics  - collection of images, videos and audio files