Silly question, but are you sure your earbuds are genuine apple?
There are two types of earphones - OMTP and CTIA. The only difference is that these swap ground and mic; most modern devices use CTIA except for things like PlayStation 4 and other devices.
If you try to use OMTP earphones with a CTIA device or vice versa, you might get that static on the line - I experienced the same exact thing when trying to use my apple head phones with a PS4.
On that note as well, Apple added some signal stuff to the mic of their CTIA earphones so they’re not even following the standard fully, so there’s a good chance that the extension cable are messing with the expected signal from the microphone.
it’s hard to put into words what I mean, but I have a feeling this is where the issue is coming from.
TRRS is a type of audio cable that stands for Tip, Ring, Ring, Sleeve connectors. It follows two standards, which are CTIA and OMTP. The main difference between the two is that their ground and microphone rings are switched. They might seem like the same but when you try to use Apple earbuds on your
thecablesland.com
The other thing is that the extension cable is acting as an antenna and picking up interference. Have you tried disabling any Bluetooth or WiFi devices around you, as well as turning off as many electronic devices just to rule out that possibility? A cheaply made and non shielded cable could be picking up noise that way.