How Can I Add Sound To My Photo Booth?

The booths do not come with speakers. The computer inside of it, however, does support audio and has a headphone jack on the back. You can easily use this jack to work with any computer speakers. A Bluetooth speaker will work as well.
You can buy any type of computer speakers and plug them into the computer. 

This is only $9.99 on Amazon 
Cyber Acoustics CA-2014 multimedia desktop computer speakers

Note to keep in mind: You can add sounds but 9/10 times your not going to be able to hear them especially if you're doing a wedding or something like prom where there's constant noise around you. We tried it and other customers several times and you really can't hear it unless its a total silence.