Echo chamber

A reverberation chamber is a special laboratory room acoustics. It is designed so that the sound is reflected on all the walls at a very high percentage and is distributed evenly throughout the room. So a strong reverberation is achieved with a long reverberation time.

Construction

The design of a reverberation room decides on its quality, which manifests itself among other things in a long reverberation time and a uniform sound field.

The walls of the room are made of closed-cell, sound- hard concrete, so that hardly any sound energy can be absorbed. To avoid resonances are walls and ceilings built not parallel. In the space plates are mounted, these serve as a " diffuser " and distribute the sound in all directions. As the source sides radiating loudspeakers are used which are placed in a corner of the room.

Since all introduced into the space objects are in sound-absorbing, the measurement technique is up to the sensors to the experimenters in an adjacent room.

Function

Ideally, therefore, prevails with the exception of the area right around the sound source ( see Hall radius) and directly in front of the walls at each place the same sound pressure. Such a sound field is called diffuse field. Since the sound rays are incident from all directions at the same time, sound pressure is present in a reverberation room no (directed ). About reverberation time measurements or by reference sound sources, the space can be calibrated. Here, the difference between the measured at any location in space, far enough outside the reverberation radius sound pressure level and sound power level of a sound source is determined. This difference depends on the frequency and remains unchanged as long as the structure does not change the space and the degree of absorption of the walls. In a reverberation chamber can therefore theoretically be determined with a single measurement, the sound pressure sound power of a source. This is for example very useful for problems in the field of sound insulation.

Application

In the reverberation chamber according to DIN EN ISO 354 ( 2003-12 ) is determined the sound absorption coefficient of materials. It may sound absorption of noise barriers according to ZTV- Lsw be measured 88 and the sound power of noise sources according to DIN EN ISO 3741 and the insertion loss of sound capsules be determined.

Typically, the following building materials and products are examined in the echo chamber:

Sound absorption: acoustical ceilings, wall coverings, furniture, theater chairs, curtains, light sails, and in automotive interiors.

Sound power: fans, motors, drives, mobile phone base stations, gas meter, vehicle components