Been thinking since first replying this morning .... and in doing so trying to visualize what you may be doing or possibly misunderstanding in relation to your query
Let me start by saying there's no known audio related issues associated with any of our B707/B720/C-135 simulations .... in regard to either the sound packs or panels and their various elements.
Commenting further in regard to your following and original posting/description as follows ....
Not sure what you mean by "lingering sound" in the case of engine startup/spool-up .... unless you're possibly confusing the light background avionics and air-conditioning systems audio for engine sound. This audio, intentionally, remains "CONSTANT" whether or not the engines are shutdown or running .... simulating an aircraft connected to an energy supply on the ground and prior to engine startup or following engine shutdown, or, powered by and its own generators whilst the engines are running.
The flap sound isn't constant and there's no way it can run constantly or even repetitively. It's just a single "CLICK" sound (no mechanical audio) representing the lever being set to whatever flap detente is selected .... that's all that's heard "from an FD perspective".
The Trim sound (I don't believe this form any part of your issue but are mentioning it regardless) is a long and continuous (not constant though) "RATTLE" whenever trim is manually set or automatically adjusted inflight per the AP .... in cases of the latter (AP applied auto-trim adjustment/s inflight) and under some conditions this can, intentionally, run for a minute or so as trim is auto-adjusted/fine tuned by the AP. See
"SECTION 6.06/B707 PANEL SYSTEMS/B707 TRIM WHEEL SOUND" in the manual.
The warning "BEEPS" (I don't believe this forms part of your issue either but are once again mentioning it regardless) are generally triggered in relation to flap setting/s or the lack of such .... and also in relation to airspeed and flap setting/s as well. See
"SECTION 6.06/B707 PANEL SYSTEMS/B707 MASTER WARNING SYSTEM" in the manual.
As I mentioned .... there's no known issues in regard to any of these details and elements forming part of these B707/B720/C-135 simulations.
Might (possibly) need to focus your attention upon how you're starting/what you're actually doing to start the engines.
Want you to pay "very close attention" to what's done, and can be seen and heard, during engine startup procedures within Benoit's following video (this's the P&W JT3D-7 sound pack for the B707-320C) ....
www.youtube.com/watch?v=9Lla0w3t2AQWhat's seen, done, and heard within the above video is precisely what one should be doing, seeing, and hearing before, during, and following engine startup procedures.
The demonstrated procedures are identical for all of our B707/B720/C-135 SERIES simulations .... albeit the engine sounds differ in accordance with the different engine types.
Want you to also relate the above video demonstrated engine startup procedures with the following quoted engine startup tutorial from our manual. PLEASE NOTE: 3 different engine startup procedures options are available .... each of which work perfectly. The procedure demonstrated within the above-linked video is the
GPU/GENERATOR ASSISTED AIR STARTUP option (#1 per the following quoted tutorial) .... the one most commonly used in R/W operations.
2 even more concise engine startup video tutorials are included within the following-quoted Engine Startup Tutorial manual extract. See
"SECTION 7.00" and
"SECTION 7.01" I don't believe placement of the FLIGHTSIM.XX/ADD TO AIRCRAFT data within the AIRCRAFT.CFG is relative to what you describe per your query .... BUT (for what it's worth) this data should always be placed at the top of any CFG between the commented out (//) title and date header information and start of the first CFG based data entry for each simulation.
The Sound Pack folder (named "SOUND" when extracted) "must" be installed inside the aircraft base pack .... this replaces the default Sound folders inside the base pack.
The Panel Sound elements "must" be installed inside the "SOUND" folder located inside "FLIGHT SIMULATOR 9" folder directory .... "NOT" inside the aircraft base pack Sound folder.
See how you go .... but I'm confident this information should sort you out/resolve any misunderstanding/s that are likely causing what you've described.
Mark C
AKL/NZ