Chirping sound when USB is connected or disconnected
It seems that the chirping is activated by the setting "Charging Sounds / Enable", and plugging/unplugging the USB cable activates/deactivates charging through the cable. Disabling that setting turns off the chirping.

So apparently the chirping has nothing to do with the SD card.The chirping sound itself seems be hardwired and not able to be changed, although it might just be that no one here has discovered the way to change it. To confuse matters further, if I turn on the charging sounds and plug in a pure USB power cable (the kind that connects to a wall socket via a transformer), there's no sound.