An adiabatic cylindrical tube of cross-sectional area

An adiabatic cylindrical tube of cross-sectional area $1 \mathrm{~cm}^{3}$ is closed at one end and fitted with a piston at the other end. The tube contains $0.03 \mathrm{~g}$ of an ideal gas. At 1 atm pressure and at the temperature of the surrounding, the length of the gas column is $40 \mathrm{~cm}$. The piston is suddenly pulled out to double the length of the column. The pressure of the gas falls to $0.355 \mathrm{~atm}$. Find the speed of sound in the gas at atmospheric temperature.