Sound Effects Free is exactly what it sounds like: a repository of various sound effects that you can use for free on your iPhone. Like many other free apps featuring sound effects, GIFs, videos, or icons, the app is ad supported and has a paid upgrade that gives you more of the sound effects and removes the ads. In this case, the upgrade is relatively limited in scope, but if you enjoy the sound effects -- which are generally decent -- it is a worthwhile purchase.
The interface is simple. When you open the ad, you'll be asked a handful of questions, but no registration or setup is required. There are 14 sound effects on the first screen ranging from a cash register to a fire engine. The second page is filled with sound effects from animals -- 15 total -- all of which are very good and recorded nicely. The More buttons don't lead to more sound effects but to an upgrade option to get more sound effects for $1.99. The upgrade is not substantial but does include roughly 100 additional sound effects in various categories. To play a sound effect, tap the icon in the menu. To stop it, either tap another sound effect or close the app. A stop button would be a nice addition just in case you don't want to play another sound effect; some continue for quite some time.
For a free app that promises sound effects, this app works as expected. The ads are not intrusive and the upgrade is not required, but the core functionality is limiting. With no menus, no settings, and not even a stop button once you've started a sound, there are better, more complete alternatives in the App Store that offer more for free and have better functionality both before and after an upgrade.