I have noticed an engine noise on acceleration on my new Highlander (Nov 2006 model). When you turn on a portable fan, you can hear high frequency fan noise (electric motor sound). The noise from the engine is very
similar to this and it starts when the RPM is 2300 or above on acceleration.

I am not sure whether this is a normal engine noise or not. Is there anyone else who
has noticed this noise?

Sounds like you might be describing the alternator Some are noisy and some just arnt. How long have you had the vehicle and how many miles are on it?

Being that this is a fairly new vehicle, I agree there may be a sound, but it probably shouldn't be as noticable as your describing.

The built date of my highlander is Nov 2006 and purchased on Jan2007.
It has run 2400 miles. The noise is not that bad but I can notice it when
I press the gas pedal.

I am not sure whether it is a normal engine noise.

(IMG:style_emoticons/default/460.gif) My 2007 Highlander does the noise as it came out from engine or bad mufler when put on gas pedal at the low speed. This noise can be described as raving of a race car and occasionally I can hear the ratling of the sheet metal ( may be heatshield sheet?) too! It's very cheap!... and annoying! This noise is getting lower when the car is at the higher speed. If your car does the same as mine, please let me know. I'm planning to take the car to the dealer next weekend to find out what's caused to this noise. Or someone in this forum may tell us if it is a normal condition for Highlander 4 cylinders?
I bought this on March and had 8500 miles. This is a 4 cylinder model with 3rd seat row option.