/ Technical information

/ HOW DOES THE BEAM SPREAD NODE OPERATE?

A beam of parallel rays from a source  enters a rotating system of mirrors which points the beam onto the outer surface of the cylinder. Before leaving the rotating system of mirrors, the beam, with the usage of a cylindrical lens, is spread into a vertical 70 cm line. This line moves by on the outer surface of the installation thus marking the fragment of the anthem played at that time in the spectral diagram.

The beam rounds the installation in 98 seconds. This time is the sum of 96 seconds of the played anthem and 2 seconds of silence. In order the beam would rotate evenly and at the required speed, a stepper motor is used in the installation.

/ HOW IS THE SPECTRAL DIAGRAM CREATED?

Sound waves are the fluctuations of the air pressure which when changed by a microphone into fluctuations of electrical current may be analysed with analogical or digital electronic devices. The analysed signal is divided into short segments (approximately 1/200 second), then it is analysed how many spectral maximums (pure tones) each length has and what is its strength as well as altitude.

The obtained data of each length is depicted in the appropriate vertical fragment of the spectrogram consisting of dots - in a column. The spectrogram of the anthem is the entirety of such vertical fragments-columns which are set in a successive order.

/ 1  "White" noise seen in high frequencies - spectral diagram of the letter "S" sung by the choir.

/ 2  Sound of orchestra cymbals which quickly fade in high frequencies, and the blue spots in the middle - the winds, violet spots - timpani.