Yes, this is perfectly normal, and is from gas in your large intestine. It is certainly nothing at all to worry about. Gas in your colon can make the enema more uncomfortable by taking up room that the enema solution would normally fill, causing the colon to expand which can result in cramping.
This same thing is quite common during a colonic irrigation, and when it happens is often loud enough to be heard in the outflow by both client and therapist.
So don't worry about it. As you continue to cleanse, you will probably find that future enemas produce less gas as your colon becomes cleared of waste matter.