spherical resonator and acoustic signal measurement apparatus have been designed and developed for measuring the speed of sound in the gaseous phase. The inner radius of the spherical resonator, being about 6.177cm, was determined by measuring the speed of sound in gaseous argon at temperatures between 293 and 323K and at pressures up to 200kPa. Measurements of the speed of sound in four halogenated hydrocarbons are presented, the compounds are chlorodifluoromethane (CHClF2 or HCFC-22), 1, 1-difluoroethane (CH3CHF2 or HFC-152a), 1, 1, 1-trifluoroethane (CH3CF3 or HFC-143a), and propane (CH3CH2CH3 or HC-290). Ideal-gas heat capacities and acoustic virial coefficients were directly deduced from the present data. The results were compared with those from other studies. In this work, the experimental uncertainties in temperature, pressure, and speed of sound are estimated to be less than