Gaming Pokeball, strange sound, Pokemon Black

[xamorok]

So I was running in the tall grass right above the city with the wind gym, and came upon a Zeburaika. I brought it down to about 10% or so, and tossed an Ultra Ball. The Ultra Ball made a different noise while being thrown, kinda of like a zoom or a screech of some sort. The Ultra Ball then absorbed the pokemon, shook while in the air, went to the ground, shook once, shook a second time, and on the second time, the pokemon was caught. This isnt the first time it has happened, as it happened while I was catching Shibishirasu in the Electric Rock Cave. This has never, EVER happened to me before Pokemon Black, so I was wondering if someone would care to offer an explanation of the odd event. I am trying to record this while it is happening so you can have some video to go along with my explanation. I am playing it on an Acekard 2, on a ds lite, and the only modification I have made to the rom is the translation patch V 7 and the only pokesav I have used was to create a celebi in order to attain a Zorua.

 

[KuRensan]

That special sound is a sort of Critical hit for a pokeball so the catch rate gets higer

 

[Vulpes Abnocto]

Too bad I can't move this to Ask.GBAtemp

Critical Capture

A totally new mechanic of capture is the Critical Capture. This feature works like Critical Hits in battle where there is a slight chance that this feature occurs. Critical Capture will be noticed when you throw the Pokéball. It'll pause in mid-air and make a metal noise. When it hits the Pokémon, it will shake once and capture. Critical captures very rarely fail and will almost always capture the Pokémon. The rarity of critical capture has yet to be calculated and this page will be updated when we know more

The critical capture feature is also used within the High Link Forest when you throw Dream Balls at the Pokémon who have appeared from the Dream World. This will guarantee their capture as you are unable to battle the Pokémon within this area.

http://www.serebii.net/games/capture.shtml