As a result, oscillations with frequencies 2 ω ω and 3 ω ω etc., where ω ω is the fundamental frequency of the oscillator, appear. Furthermore, the frequency ω ω deviates from the frequency ω ω 0 of the harmonic oscillations. See also intermodulation and combination tones. As a first approximation, the frequency shift Δ Δ ω ω = ω ω − − ω ω 0 is proportional to the square of the oscillation amplitude A :