Need advise why exhaust note is louder?

[dan7uk]

Replaced my oem exhaust tips with Air Flow 18" slash cut truck stacks.  My pipes are unmolested factory still has the piggy's.  I've notice the exhaust note is louder since I've installed the stacks.  Don't understand why extending the tips about six inches would make it louder.  From the piggy's to the manifold is the same, can someone explain why?

[Moonshot_1]

I'll take a crack at it.

It probably isn't any louder. The sound waves simply have a more direct line to your ears as they are no longer obstructed by saddlebags, a tire and other parts of the bike as the sound exits your pipes.

[dan7uk]

Forgot to mention it's a 99 tourer with oem hard bags.

[Bone]

It changed the tone of the note.
It's now easier to hear you know like when a person doesn't hear his wife.

[Tropic traveler]

Classic case of droning into an echo chamber.
Had a similar problem with my glass pack mufflers dumping the sound into the longer tips.
Fixed it by extending the exhaust dump to the end of the tip. No more echo chamber effect.

[Rio Wil]

Same effect as playing music through a 1 inch tweeter or a 4 inch speaker.  Then sound pressure pulse came out the 1 inch piggie and directly in to the atmosphere....ie a 1 inch tweeter. With an extension covering the piggies and making the sound pulse travel further before entering free air, it allows the sound pulse to expand to 4 inches and slow the pulse down thereby enlarging the pressure wave front lowering the tone .

[Farther]

Just like using a megaphone.