DESCRIPTION:
For further informations:

daniele.mirabilii@mail.polimi.it
danielemirabilii@gmail.com

The aim of this project is to try to emulate sounds and operational procedures of an analogic Theremin (a popular electronic instrument) including pitch and amplitude control of a sinusoid, with a system made by a well-known single-board computer called Raspberry Pi3 and two ultrasonic distance sensors.

The main goal is to reach the possibility of controlling such parameters using just two hands or objects with flat surfaces, without any physical contact between the “instrument” and the user, just like the original one.

Instead of using modulated electromagnetic waves as in the original Theremin, the here described system uses ultrasonic waves: the main difference is that, while in the analog Theremin the user’s hand works as a grounded plate (the performer's body being the connection to ground) of a distance-variable capacitor in an L-C (inductance-capacitance) circuit, this digital system provides a sort of SONAR system to determine the distance.

In fact, the system uses a pair of ultrasonic sensors, both with one ultrasonic transmitter and one receiver: the first one emits eight impulses at 40 Khz and the second one tries to capture the echo signals coming back from an obstacle. The distance measure is accomplished by a simple code that applies the space-time equation starting from the time passed between the emission of the transmitter and the echo signal reception.

This concept represents the same operating way of a biosonar, an echolocation used, for instance, by several kind of bat species or toothed waves (such as dolphins or belugas): that’s the reason this project has been called BaTHEREMIN.

At last, the system presents a further feature: using a high-sensitivity microphone sensor, it’s able to capture a really fast audio transient (such as a clap or a pop/snap) and to measure the time passed between the first transient and the fourth one. This feature has been used to apply an amplitude modulation (some sort of tremolo effect), based on a time beat produced by the user.

For further informations:

daniele.mirabilii@mail.polimi.it
danielemirabilii@gmail.com