My best guess is that your sound is stimulating some capacitor connected to a voltage-controlled clock oscillator in the laptop. The voltage provides by the sou

My best guess is that your sound is stimulating some capacitor connected to a voltage-controlled clock oscillator in the laptop. The voltage provides by the sound is causing the frequency of the VCO to move around slightly. 24M is a pretty common frequency in electronics for use as a general-purpose digital clock.