12 years on flightlines with F-4's, F16's, F15's, and especially B-1's, tell me that there is a perceptible difference in the loudness.
According to the Navy, the F15 has 144 db in Mil power and 149 db in afterburner. For acoustics, 10 db is the doubling factor, so the F15 is half again as loud in afterburner.
Chart from document below:
http://www.nrac.navy.mil/docs/2009_FINAL_Jet_Noise_Report_4-26-09.pdf