Why are my earbuds making dolphin noises?
It's not a driver/software/audio card issue, because the dolphin noises don't occur with other headphones or when playing music through the speaker (via Buscar above). It's probably a bad ground (via soulshined above), but without stripping the wires and testing each connection, it's impossible to say for sure.

I went to the Apple Store with a Genius Bar appointment for another issue (cracked iPhone screen) and asked them about it. Apple replaced my headphones for free.