Photoacoustic spectroscopy has one important advantage: its sensitivity is proportional to the excitation light power and thus the performance of PAS-based sensors can benefit from a high excitation light power. We developed a cavity-enhanced photoacoustic sensor in which a photoacoustic cell was placed into a high-finesse optical cavity. A signal gain factor of 166 was observed. For C₂H₂ detection, a 1σ detection limit of 0.45 ppmV was obtained at atmospheric pressure with a 1 s averaging time.