this is usually caused at the universal
joint down at the floorboard. A good
silicon spray should quiet it down.

Hi Wayne,
               Mine has done the same for years.
I came across an advice sheet on the net some place.
It shows a change of bushes on the steering rack.
The ones that hold the rack to the bulkhead.
I took it to my Toyota dealer but he just said rubbish
no such mod.
But get someone to sit in seat, open bonnet.
look at the steering rack and see if it moves a little
when you exercise the steering wheel.
Mine does.
And noise is from there.
But only in cold weather.
Get Google and search under Toyota Rack noise.
or some think like that.
I will try and find it again.

let me know if yours moves.

cheers Johnny UK.

Similarly, my 99 Camry does that but the problem only started THIS winter!!

Same thing with my 99'  This drove me nuts and sounded like it was coming
from under the horn area of steering wheel. Almost sounded like a singing
noise. I found the source to be coming from where the steering column goes
through the floor board.  There is a collar there that just needed to be
sprayed with wd-40.  Its been over a year now since spraying it and no
more noise.  Give that a shot.

Same thing with my 99'  This drove me nuts and sounded like it was coming
from under the horn area of steering wheel. Almost sounded like a singing
noise. I found the source to be coming from where the steering column goes
through the floor board.  There is a collar there that just needed to be
sprayed with wd-40.  Its been over a year now since spraying it and no
more noise.  Give that a shot.