I've noticed since my car was new that there is a continuous "chirp" in my engine that starts at around 75 KM/H and goes away when the car reaches around 90 KM/H.

This only happens when I am on the throttle. When the engine is under load, or going up a hill, it is there...when I am going downhill, the noise goes away.

I've mentioned it to the dealer at each service and even taken the advisor and manager for a drive in which they both acknowledge hearing it, but don't have an answer for it.

Any thoughts?

 

i have the same problem, it sound exactly the same as how you mentioned. but for my case the sound occurs in different speed range, mine starts at 50km - 60km, after 60km it goes away and for highway driving the noise comes back at 130km - 140km. and the situation is about the same as yours, when the engine is under load the noise is there, when it's going downhill, the noise goes away. its pretty strange. a few member on this forum had this problem with their tsxs too and they describe the noise as a whinning noise.
i like how you put it as a bird under the hood, it sound so much that hahaha and i've mentioned it to the dealership and they heard the weird sound but they couldn't locate where the problem is.
by the way what trannmission is yours, mines an AT and most members who complained about this problem here has the AT tsx too.

 

Slightly slipping accessory belt

 

Mine is also A/T. I'm going to go to the dealer tomorrow and have them check the belt.

Any other thoughts?