The reason for me was the C-State. If it is enabled, the CPU makes that noise. Power consumption may go up, but I enjoy the silence. [URL] 
The computer chirps after a short warm-up period when connected to the power adapter (130w). The noise comes from the left side (where HDMI and USB-C ports are). In battery operation the chirping is much quieter. Built-in Micron 2200S NVMe 1024GB, no additional HDD, 16 GB RAM, everything as ordered, no retrofitting.
Inspiron 15 7590 chirping