The Binaural Ogunator is part of the project Erzulies Traum.

The Binaural Ogunator is a kinetic sound sculpture using silk, computer controlled motors and 2-channel sound system. Two triads of sinusoidal signals are slowly changing frequencies against each other (binaural beats) to create a permanent shift from deep drones to a fast 6/8 rhythm and back.
The sound is synchronized with 3 computer controlled motors moving flags of red and black silk.

video

photos

The sound of the Binaural Ogunator is composed using a phenomenon known as binaural beats: two sinusoidal signals with slightly different frequencies produce a low frequency pulsation dependent on the difference of the two tones. Normally you get the best effect by listening to it with headphones, each signal in one ear. For the Ogunator we used a 2 channel sound system so people can move around in the room.

We used a custom max/MSP patch to create 3 sinusoidal signals at each channel. The tuning of the signals of one channel constantly changes over a period of 11 minutes to create a shift from deep drones to a fast 6/8 rhythm and back.

Wandering around in the installation the listener is constantly changing the mix of the resulting pulsations because of his position to the speakers and reflections in the room. The accentuation of the pattern is changing and shows the ambiguity of the 6/8 rhythm.

Tuning of the sinusoidals to get the binaural beats of the Ogunator:

For a short moment when both channels are in tune (state A) there is no puls. As soon as channel 2 starts changing frequencies a slow pulse developes, speeding up over 10 min time until state B.  Because of the different shifts of the 3 sinusoidals there is a resulting rhythm which is the basic pattern of african 6/8 rhythms and also the rhythm played in the ritual we visited. In state B the rhythm reaches the tempo of the drumming in the ritual.

motor control:

For spinning the flags we use motors for car windscreen wipers, controlled by a custom software written in max. The software is talking to an Arduino board to change direction and speed of the motors using pwm signals, then send to two RN-VN2 modules.

The motors have 6 different states of movements dependent on the tempo of the music:

1. don’t move
2. shaking
3. slow movements (5 possibilities differing in acceleration and speed)
4. rapid movements (5 possibilities differing in acceleration and speed)
5. spinning
6. slow down

There is no abrupt transition from one state to another but a continuous shifting of probabilities to choose a certain state. This probability shift is the same for all three motors, but the decisions what to do is choosen seperatly for each motor.

So the flags behave in a related way but seem to have their own plan, moving sometimes alone, unisono or in call and response style.