My rabbit is making a weird noise. It kind of sounds like wheezing and a mix of a cough with bad phlegm and the crunching sound when rabbits eat pellets. I don't know if this is normal. What should I do? I am very scared for my rabbit. Here is the link to the audio of my rabbit's breathing: https://clyp.it/oqwgyxnw
It is difficult to hear your rabbit breathing in the audio recording. There are a number of issues that can cause breathing noises in rabbits, the most often diagnosed is Pasteurellosis. It is important to take your bunny to a good rabbit vet to get a proper diagnosis.
If the diagnosis is Pasteurellosis you and your vet may or may not decided to treat it. Rabbit health and digestion is dependent on bacteria in the gut, disruption of these bacteria from antibiotics can lead to difficulties. In some cases it can be difficult or impossible to completely eliminate the infection. We have an 11 year old rabbit who has been living with us for 9 years, with the snuffles (Pasteurellosis). Sometimes Harmony wheezes, some times she has coughing/sneezing fits, mostly she is is just fine.
The crunching sound you mention, is not a sign I would relate to the snuffles, so a vet visit is definitely needed for good diagnosis.
The crunching sounds when eating could be a sign that his teeth are grinding. Many small animals like rabbits have continuous tooth growth throughout life.
Is he offered a mineral block, salt lick and/or flavored wooden blocks? The salt and fruit flavors attract your bunny to chew them (hopefully instead of plastic litter box, cage wires or water bottle) to keep teeth at a healthy length.
If you take him to the vet to get his upper respiratory checked out, a general physical examination should be done, but just in case ask said vet to check his teeth. Overgrowth can end in mouth sores, the loss of the ability to eat, and vets can manually grind down any extra growth.
Also imagine when YOU have a cold or upper respiratory infection. When you chew your food and can't breathe through a stuffed up nose, you inhale while chewing to breath, thus causing a more noticeable and loader chewing noise. This may sound silly, but is still a possibility.
Either way, sounds like a necessary vet visit as said by previous answer. Hope your bunny gets well soon.