Game Boy Advance Possible speaker issue GBA SP

[SneakyFoxxo]

Hello! New here.

I have had my GBA SP for a very long time, and I've noticed that my unit seems to be having an issue with audio. I can hear the audio fine, but there is an electrical hum. When using a headphone adapter, I can hear the same static. It's not TV -like static, its more of an interference like a guitar humming when plugged into a noisy power source. That leads me to believe that there might be some sort of cross talk or grounding issue. A few things to clarify:

• I have been inside the SP before, and it's totally possible that I may have minimally damaged the speaker
• The model is AGS-001
• All of the tests were done on battery, not plugged into the wall
• The issue persists between the GB mode & GBA
• The different modes produce different results
  • GBA frequency changes when the backlight is toggled, somewhat lower frequency when backlight is off
  • GB is generally higher pitch and does NOT change when the backlight is toggled
• There is a constant low droning electrical noise that is consistent between the modes, with or without headphones
• Connecting to a speaker system produced the same results, but the speakers need to be turned way up to hear the noise

A few questions come to mind:

• Is this normal?
• Is this a defect that happens over time, or were they like this from the factory?
• Is there anything I can do to mitigate or eliminate the noise?
• How likely is it that I'm going to have to replace the speaker?