Last Tuesday, October 27, 2020, the participants of the "Audio & Electroacoustics" department of the AES Aural Student Section had a meeting to define the project named "Construction of tunable capacitive microphone 2.0". It will be presented in the Audio Expertos 2020 event on Tuesday, November 24.
We defined a 2.0 model of the microphone, dividing the project in 3 parts for its development, "acoustic concepts", "mechanical behavior of the capsule" and "electrical diagrams". Within these three parts of development we ordered each procedure to achieve the construction of the same:
a) Acoustic concepts: understanding Ernst Chladni's discovery and his studies on surfaces and vibrations, we try to transpose the sound waves into electrical information. By means of vibrations that these waves produce in different points of our microphone membrane, perfectly tensioning by two rings of adjustment, allowing to take the entered and codified signal, and thus to tune in frequency.
b) Mechanical behavior of the capsule: based on the designs proposed by our collaborator Horacio Rico, we opted for the construction of a backplate with several bronze pins, located at specific points in reference to the diaphragm that allow the collection of the acoustic signal vibrations, each point tuning a specific frequency. The pins will be conjugated and distributed in specific tuning areas and will be activated independently by a selector that will give them the voltage that they require for their operation in relation to the acoustic impedance they request.
c) Electrical diagrams: we understand that the microphone in its complexity is entirely connected and each part is important for making decisions about the components that we need to use for the power supply and the correct operation of the other parts. Therefore, starting from its main power supply, we choose an external power supply provided by two 220W 12V transformers in series, giving us 48V as a result, which will then be cut by a multiplier that distributes and, through an independent circuit, raises the voltages for each part. This one would feed to the circuit of the boostrap where the same one is going to make a redistribution of voltage, where part of her will be destined to the polarization of the capsule, granting the necessary voltage to him so much to the membrane as to the different sets of bolts in the backplate.
