1. B. Tunnel-to-Flight Condition Processing
2. Auralizations of each of the twenty-four aircraft conditions listed in Table 1 were performed using the approach described above. The aircraft trajectory, speed, operating conditions (e.g., throttle, flap, gear settings), etc., were as specified by Thomas et al.4A uniform atmosphere at mean sea level ISA conditions (15°C temperature, 1 atm) and 70% relative humidity was specified, and atmospheric absorption was calculated using the ANSI S1.26-1995 standard30with the Zuckerwar update,11as described by Rizzi and Sullivan.26The ground was considered acoustically hard, and the receiver was either flush to the ground, resulting in a 6.02 dB increase across all frequencies, or at the certification microphone height of 3.94 ft. The approach observer position was located on the flight path at a point where the aircraft passed 394 ft. overhead on a 3-degree glide slope. The sideline observer position was located at a lateral distance of 1476 ft. and at a downrange distance where the aircraft reached an altitude of1000 ft.4Thus, the sideline observer locationdiffered slightlyfor eachaircraft.
3. Summaries of the change in EPNL (generated from auralization) of the N+2 aircraft relative to their respective reference aircraft are shown in Figure 5 and Figure 6 for the approach and sideline conditions, respectively, for the 3.94 ft. microphone location. Here it is seen that the introduction of ITD noise reduction technologies yield about 0.5-1 EPNdB additional reduction in EPNL relative to the reference vehicles. It is interesting to note that the T+W160-GTF in the SA class achieves comparable noise reduction on approach and sideline, whilst the LTA class aircraft achieve substantially more noise reduction on approach than on sideline. Also with respect to the LTA class, the aircraft configuration (T+W, HWB and MFN) has more to do with the amount of noise reduction on approach than does the engine type (DD vs GTF). This is readily seen by comparing T+W301-DD and T+W301-GTF with HWB301-GTF and MDN301-GTF. Conversely, for the sideline condition, the engine type has more influence on the noise reduction than does the configuration. Compare T+W301-GTF, HWB301-GTF and MFN301-GTF with T+W301-DD. The last two observations are consistent with the work by Thomas et al.4in which it was shown that the contribution of airframe noise sources is close to or above the engine sources on approach, and well below the engine sources at sideline for the T+W301-GTF and HWB301-GTF vehicles (see Figures14-17 inthe subject reference). Figure 3: ComparisonofPNLT for selected LTAclass aircraft onapproachat a simulated ground microphone. Figure 4: ComparisonofPNLT for selected LTAclass aircraft onapproachat a simulated 3.94 ft. microphone.