5. On a warm day (32C) you hear an ambulance behind you, so you pull over to the side of the road and stop. You happen to have a microphone with you and notice that the frequency of the siren changes from 744 Hz to 661 Hz as the ambulance passes you at a constant speed. Determine the ambulance's speed and siren's frequency. Hint: solve for the source frequency using two Doppler equations, then equate them to find the speed. 6. At a distance of 20.0 m from a point sound source, the intensity level is 95 dB. a) Calculate the intensity of the sound source at 20.0 m and the power output of the source.