In some dance songs, there are sound bites used before the break (drop). Do sound bites fall under fair use, or does a producer need permission to use them legally?
You are required to gain clearance, otherwise the owner of that sample could demand payment from you.
Sampling potentially violates the law regarding two separate copyrights, the copyright of the musical composition (the PA Copyright) and the copyright of the sound recording (SR Copyright). You need to obtain the permission of those copyright holders before using the original song or master. The process of getting that permission is known as clearing the sample.
Another option would be to ask those artists where they found those royalty-free samples. Though there are sample collections that are sold on CD or DVD, there are also repositories of sound bites and samples that are in the public domain. One excellent source is the Prelinger Archives. Another is freesound.org.