Click and whirring sound behind the heat shield
 

I have two noises that sound like they are coming from behind the heat shield under the hood of my 1993 Honda Accord automatic.
The first sound is one loud click or pop that occurs every couple of minutes for about 1/2 hour after the engine is turned off.
Doesn't matter if i've just driven a few minutes or all day.
It's not the popping and crackling sound like when the metal is cooling. It's just one pop or click.
The second sound is kind of a whirring sound that happens when the engine is cold or warm.
When I accelerate it's a higher pitch,and when I let up on the gas, it's a lower pitch.
This is a constant sound. Is it possible it might be an exhaust leak?
Thanks.

Your first sound is likely metal contracting. The second sound may be a bearing noise. For example it could be the PS pump, alternator, A/C, distributor, T-belt tensioner, balanced shaft tensioner, etc. etc. Noises are one of the hardest things to diagnosis over the web.

Thanks for your reply.
I know it's hard to diagnose without hearing the sound, but it gives me a starting point.