Two speakers, A and B, produce
identical sound waves. A listener is
3.20 m from speaker A. The listener
finds the lowest frequency that
creates destructive interference at
his location is 72.4 Hz. How far
away is he from speaker B?
(Hint: v = A f = 343 m/s)
(Unit = m)

Air enters a gas turbine with two stages of compression and two stages of expansion at 100 kpa and 17°c. this system uses a regenerator as well as reheating and intercooling – the intercooler returns the air to the inlet temperature. the pressure ratio across each compressor is 4 ; 300 kj/kg of heat are added to the air in each combustion chamber; and the regenerator operates perfectly while increasing the temperature of the cold air by 20°c. determine the system’s thermal efficiency. assume isentropic operations for all compressor and the turbine stages and use constant specific heats at room temperature. (0.378)