4. Just by how they sound.
4/5: This is what a 4/5 port Thunderbolt sounds like
http://www.youtube.com/watch?v=_-CwbUOf_Zo . The only other 4/5 port siren I believe is the Federal model 2t (
http://www.youtube.com/watch?v=rZj5_owHSQw)
8/10:
http://www.youtube.com/watch?v=t4NmwLO-9Is Found in ACA Hurricanes.
9/12:
http://www.youtube.com/watch?v=3tiG29MjLaM
You can usually tell what Port Ratio a siren is by the sound and frequencies it outputs,
Here is a chart I found of port ratio's and there frequencies.
NOT MINE
3.....172.5........F3......(174.6)
4.....230...........A#3...(233)
5.....287.5........D4.....(293.6)
6.....345...........F4.....(349.2)
7.....402.5........G4.....(392) . . . . STL-10 . . Federal Signal claims 405 Hz
8.....460...........A#4...(466.1). . . Allertor, Banshee, Hurricane MKII, 20V2T, model 7
9.....517.5........C5.....(523.2). . . Allertor, Banshee, Screamer . . . FS model 5AT (claims 521 Hz), P-20 RM-130
10...575...........D5.....(587.3). . . Hurricane MKII
11...632.5........D#5...(622.2)
12...690...........F5......(698.4). . . STH-10, Allertor, Hurricane MKII . . .FS model 5A (claims 694 Hz)
15...862.5........A5......(880)
16...920...........A#5...(932.3). . . 20V2T
9....421.5.........G#4...(415.3) . . . E57 @ 2810 rpm
2001-130......12? ports....750 Hz....F#5(734 Hz)
Model 2, 2T......................427 Hz....G##
Eclipse...........8 ports.......525 Hz....C-5(523 Hz)
Dual-toned sirens
Ports..................Notes.......Musical interval.......Resultant.........Siren
4/5...................A#3 / D4..........Major 3rd...............A#1...........Thunderbolt, 2T
5/6....................D4 / F4............minor 3rd...............Bb1...........Thunderbolt (Depends upon which of five chopper speed settings)
6/10..................F4 / D5............Major 6th..............A#3............Decot
7/10..................G4 / D5...........diminished 5th.......F3..............H.O.R.
7/12..................G4 / F5............7th........................D4...............2t22 advertised, maybe not produced
8/10..................A#4 / D5.........Major 3rd..............A#2............Hurricane MKII
8/12..................A#4 / F5..........5th.......................A#3............ACA models: Allertor, Super Banshee, Cyclone, P-50, 550AT, T-135,
8/16..................A#4 / A#5.......Octave....................................(Carters @ 50Hz would be G), 20V2T
9/12..................C5 / F5............4th.......................F3................SD10, Allertor, Banshee, Howler, 500T, P-10
9/15..................C5 / A5............6th.......................F4
10/12................D5 / F5............minor 3rd..............Bb2.............2T22, Allertor, Hurricane MKII, 500T (creates a Bb-D-F major chord!)
10/15................D5 / A5............5th.......................D4................Sentry 40V2T
10/16................D5 / A#5..........minor 6th.............F4.................Decot
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