Found: Loud Bird In Singapore's Estates

I finally did some research and figured out the kind of bird(s) which make the loudest sound in many estate around Singapore. Apparently it's the male and female version of the Asian Koel that monopolised the soundscape every morning and sunset (talk about compatibility!). They're from the cuckoo family. They make the piercing sound in the morning and seem more common in the older estate with the abundance of trees.

This is a good video since it showed both the male and female sounds in the same clip.