Hi there. I just bought 4 days ago, my MacBook Pro 2018 Touch Bar 15 inch, i7, 8th gen. First time with Apple.
I am in UK.
Learning my way with the system and all related, I haven't yet installed any software.
I Have a crackling sound as well in the speakers. I recorded it for evidence.
I have to mention that I followed the standard setup, and even done all the updates available in my AppStore.
First time, yesterday (3 day having the laptop) just playing around finding my way in Garage Band, started the crackling sound. I thought, what a ... might be something I did with the sound while messing around with the instruments in the track. Ok; left it and closed down not paying to much attention, as after that I went on music and Youtube to see if really is a speakers issue or not. For the moment not hearing an issue noise anymore, carried on with my learning around.
Next day (today), I played some music from my external hard drive via iTunes and I am not sure how long after the first song, must have been at least 1 hour for sure, I had the crackling sounds, regular at every about 10 seconds or so, had recorded them on my phone.
Turned off the music, had a lunch break while I was thinking of what I will intend to do next: went o the forums, and for my surprise to find out many, many other users and many forums that complain with the same issue. A small relief, that is not my machine only.
I truly believe that is a software issue, or some incompatibility of settings between the components. Just my first opinion.
While I was looking on the net for this, I played some more songs, with no further issues. Indeed was not over 1 hour though, ....will keep on testing next day.
I will write or contact on phone Apple support as well.
I will try to look into how to change the audio sampling from 44 to 48Khz as others were suggesting (how do you do that??)
Further more, I will NOT update to Mojave until more of the users with the same issue, will confirm 100% that this solved their issue definitely.
I will not give it back for exchange because that will not solve the issue, (I have experience from previous situation with some other big brand product) that you are giving back something, and get a second one with the same or an extra issue. ...more, I have learned that even the big brands, they are not giving you for exchange on warranty a brand new machine, but a revised, refurbished one that was returned, they "fixed it", cleaned, repacked and here you go..
...no thanks. Not having any other issue, I will wait a bit patiently for Apple's solution....and if others will confirm that Mojave solved their speakers crackling issue, than I'll go for the Mojave.
Looking forward to hearing from you all.