They were with the problem that the housing of the instrument reflected noise into the microphone, which affected the accuracy of the measurement. Therefore, housing could not have the usual form of box, and they decided to be conical. However, this reference to physical laws and technical needs is a true blessing. Undo helper microphone used to be at one end of a cable; the other end is connected on a pretty square box subject by someone or something. The user had to hold the instrument with one hand and handle it with the other, and also needed a third hand to hold the microphone. But it is a universal truth that there is nothing worse than a helper with a unoccupied hand. Therefore, Bruel & Kjar decided to eliminate the most important source of errors the Assistant by mounting the microphone directly on the instrument. To do this he had to give the instrument an exterior form that will prevent the reflection of noise.
The resulting creature seems to be a great success. We say seems because if you’re not a Technical Acoustics, is difficult to say. Seen from today’s perspective of our daily life replete with intelligent technology of small size (mobile phones, mp3 players, calculators the size of a credit card, etc.), 2203 model does not seem especially lightweight or small, but if we take into account the technology of the time and the limited number of manufactured units, it was quite an achievement and all our competitors copied the concept of the housing in a cone shape. Let’s take a look at some of its technical advantages and limitations. Inside the model 2203 in 1962, the only teams that used transistors were the model 2203 and 2211 (sound limit indicator). All others had valves. Transistors which existed at that then were germanium and generally had high gain, low noise current ybaja of leaks that was required.