This study examines the noise radiated from hypersonic boundary layers generated on a flat plate, including the effect on an impinging shock wave. The Focused Laser Differential Interferometry technique was used to quantify the acoustic noise at 5 and 13 mm above the surface of the plate. The power spectral density of the phase fluctuation spectra and the Sound Pressure Levels show an increase in the density fluctuations for frequencies between 22 and 710 kHz when the boundary layer is turbulent and when a shock interacts with laminar and turbulent boundary layers. In contrast, the RMS of the density fluctuations normalised by the mean density shows an increase in the density-based turbulence intensity level for the turbulent boundary layer only above 300 kHz. When an oblique shock interacts with the boundary layer, the density-based turbulence intensity levels are significantly lower than in non-shock interaction cases. In the laminar boundary layer, the levels are 35–40% lower; in the turbulent boundary layer, they are 45%. This indicates that the increase in mean density across the shock dominates the increase in the absolute fluctuation levels. This study concludes that the hypersonic turbulent boundary layers radiate a significant amount of acoustic noise and indicates that the density-based turbulence intensity levels approximately half when an oblique shock wave interacts with these boundary layers.