The primary objective of this work is to investigate lip-thickness effect on the various acoustic emission characteristics of Hartmann whistle. Nozzle-to-cavity distance (stand-off distance), cavity length, nozzle pressure ratio and lip thickness form the pertinent parameters of the present study. Two lip thicknesses considered in the present study are a thick-lipped cavity (5 mm) and a thin-lipped cavity (1 mm). Although lip thickness has negligible effect on the resonance frequency, it has significant influence over the sound pressure levels generated. The results showed that thin-lipped-Hartmann whistles could emit up to 2.4 times the acoustic power as compared with thick-lipped whistles.