9v Battery Question

My project consists of three LED drivers, an audio module, and an amp for the audio module. When I hook up the arduino using a wall wart, everything works fine. When I hook it up with the 9V battery, the LED flickers when a sound is played. I'm assuming the 9V doesn't have the power bandwidth or amperage to run this. I have to stick to using a 9V due to size. What can I use to alleviate this? A capacitor maybe?

Perhaps six AAA batteries would not be too big?

Thanks for the suggestion but the project is a prop gun (Stormtrooper E-11 blaster rifle) and I hollowed out a portion of resin just for it. Do I have any options?

Perhaps one of those expensive Lithium-based 9V batteries would have enough power.

Possibly a NiMH rechargable 9V gives more current than alkaline? Not sure.

Also there are 5V boost circuits available that allow a couple of AA cells to directly provide 5V power.

Some measurement of the current your set-up is taking would be useful data.

I've ordered a Litium Ion one. It says its 1200mah. I'll see how that goes.

Your lithium ion battery should help. Even a NiCd would have helped you. You aren't running into a capacity problem, you are running into an internal resistance problem. Even a NiCd battery with its lower capacity should have low enough internal resistance to power your circuit, a lithium ion based one should be even better. I wouldn't pull over 100 mA from an alkaline type anyway and that is pushing it.