Complex sentence: A photoacoustic Doppler effect (PAD) is a phenomenon caused by frequency shifts in the Doppler effect where acoustic waves absorb flowing particles within a medium that is excited by visible light.
Split into simpler sentences: A photoacoustic Doppler effect (PAD) is a photoacoustic doppler effect. The phenomenon is caused by frequency shifts in the Doppler effect where acoustic waves absorb flowing particles within a medium that is excited by visible light.