The sounds of friction

Audio files created by Giorgio Divitini (June-July 2005), by analysing the oscillatory part of the time evolution of particle number 49 in the lubricant chain trapped between two sliding periodic sinusoids (the substrates).

The lengthscale ratio r is defined by r=a₀/a₊=a₊/a_-.

The spring constant of the springs joining the masses is K.

Phenomenological dissipation produces a force on particle i equaling - γ (2 v_i - V_ext), with γ=0.1.

The audio files are produced at such a sampling rate that 0.1 simulation time corresponds to 1/44100 second.

Sounds for r=3/2

Initial 1/f region: K = 0.01, 0.015, 0.02, 0.03, 0.04, 0.05, 0.07, 0.1, 0.15;

first plateau (4/3): K = 0.2, 0.3, 0.4, 0.5, 0.7, 1.0, 1.5, 2.0;

transition region: K = 3.0;

second plateau (1/3): K = 4.0, 5.0;

transition region: K = 7.0;

final plateau (2/3): K = 10, 15, 20, 30, 40, 50, 70, 100, 150.

Sounds for r=golden mean

Initial 1/f region: K = 0.01, 0.015, 0.02, 0.03, 0.04, 0.05, 0.07, 0.1;

commensurate sliding plateau (1/1): K = 0.2, 0.5, 1.0, 5.0, 10.0, 50.0, 100.0, 150.0;

large-K transition region: K = 180.0;

large-K incommensurate sliding: K = 500.0, 1000.0.

Sounds for r=π/2

Initial 1/f region: K = 0.01, 0.015, 0.02, 0.03, 0.04, 0.05, 0.07, 0.1;

incommensurate plateau: K = 0.2, 0.5, 1.0, 2.0;

transition region: K = 3.0, 4.0;

large-K region: K = 5.0, 7.0, 10.0, 20.0, 100.0.

The present document and the associated audio files constitute an addition to Giorgio Divitini's thesis Spectral Analysis of a Lubricated Friction Model, Università degli Studi di Milano, 2005.