After I turn the car off there is now a whistling noise from the engine area that changes in pitch. It continues for several minutes. I opened the hood and it appears to be toward the front of the motor and lower down. I had not noticed this before and I have had the car for 9 months. Is this normal?

 

My car makes several odd noises for a minute or two after shut-down. Can't say it's exactly as you describe, but it is different than any other car I've ever owned.

 

Ours has done this for thousands of miles. I'm leaning towards something with the A/C, as I recall, I only hear it on hot days.

 

I think you are correct. Thanks.
I did some quick research and it is a normal noise as explained below:

Many times a friend or customer will ask me to come listen to a strange hissing sound when the automobile is turned off. Naturally, this is after running the air conditioner for a while on a hot summer day. Although this hissing noise, sounds like a bad noise, it's actually a good air conditioning noise.

The hissing sound is caused by equalizing pressure. When the car AC system is running there is a high side and a low side that's divided by either an expansion valve or an orifice tube. These two separate sides of the system are necessary for proper operation.

When the vehicle is turned off or the air-conditioning compressor clutch is disengaged the system will equalize the pressure. The hissing sound is the Freon from the high pressure side slowly feeding into the low pressure side and this is completely normal.

 

I vote for the a/c too.

I have noticed only after I shut down in the garage without first manually turning off the a/c, I get that strange whistling noise too.

My other car makes about the same type noise also, just not a pronounced.