Acoustic Chamber

Acoustic ChamberIn some cases, in order to research in radiolocation, antennae radiation, microwave radiation etc. it is necessary to eliminate all the side radio signals, both external and reflected. The acoustic chamber is used for these purposes. The chamber is made in such a way, that external waves do no enter it and the internal ones are effectively absorbed by its walls. The measuring equipment in such chambers is not affected by false signals. It only registers the ones that are relevant for the experiment. The size of the chamber is optional, depending on the purposes of the experiment. For instance, a chamber might be large enough to house a military plane. The dimensions depend on the minimal distance from the transmitters to the receivers. They might be quite large. However, research may be carried out on smaller models, if you alter the length of the wave accordingly. All the surfaces of the acoustic chamber are covered with radio-absorbing coating, made of special materials. The material should neither conduct nor isolate electricity. Radio waves must be extinguished when they penetrate into such kind of material. The material may be rubber-like, containing a mixture of iron and graphite. It may be presented by ferrite blocks to perform measurements in the microwave range. The surfaces are shaped specifically. Pyramid-shaped absorbers are used most frequently, as their structure absorbs most efficiently. The efficiency of the chamber is determined through the minimal radiation frequency, when the reflection from the walls starts to exceed the reflection of the high-frequency waves significantly. Pyramid-shaped absorbers are most efficient, when affected by radiation with the length of wave ?. The height of the pyramids should be approximately ? / 4. So, the higher is the pyramid, the more efficient is the chamber. However, it is also more expensive and has less internal working volume.There must be no extra items in the chamber, especially metallic ones, as they may act as reflecting surfaces. Plastic and wooden items may be present if necessary. Minimize the number of the cables and place filters inside the chamber to minimize external electric hindrances. The screening of the external impacts helps to extinguish electromagnetic energy of 60-120 dB in the frequency range of 10 KHz - 100 GHz.There are analogous sound acoustic chambers as well.

Category:

Science & Technology

Tags:

• accuracy of measurement
• EMI
• radiowaves