Why does my computer have fuzzy audio when connected to Bluetooth?

Your system has two analog outputs the built-in speakers and via the headphone jack for a wired headset. Do both of these sound OK? If they do you’ve removed the DAC logic within your system. Make sure these are working first.

So now let’s look at Bluetooth here the signal is kept in its digital form and sent over the air to your Bluetooth headset or speaker, then its converted to the analog signal to drive the cones headphone or speakers

Now the next issue is the source of your source of your audio is it streamed or a local file? See if the local file is better than the streamed source. If streamed are you connected via WiFi or via a wired connection? You may want to see if the Ethernet connection works better

It’s possible your AirPort board is bad or your WiFi router, and lastly if the streamed audio is bad via the wired connection then your ISP connection is the issue.