I've noticed this high-pitched sound coming from the top-left part of the keyboard. I understood it might be due to some capacitors resonating or the i3 switching C-states. The sound is more pronounced when on battery power. I noticed the same sound coming from the AC adaptor itself.
The CPU downclocks only when the appropriate slider in Lenovo power management is set to auto adjust and it in no way affects the chirping.
Due to tolerances, the capacitors in some systems may resonate at high frequencies as the CPU's C-states change. Not all systems will emit these sounds, and due to differences in environment, background noise, and individual user hear acuity, they may not be noticable.
This is considered a normal phenomena. Some customers have reported success using ThrottleStop to limit CPU fruquency changes..