Whining Noise/Won't turn over?

Okay so this may be a long one but I appreciate any help I can get!

Last week I started my truck in the morning and noticed a whining noise in the cab. I can't pin point where it was coming from so I took it into a garage and he said that the noise was coming from the transmission and that maybe it was the filter or a pump within the transmission but that he couldn't be exact without opening the transmission. He said that as long as it wasn't slipping or kicking to leave it unless the noise got louder. He never 100% gave me a reason for the noise.

Then today after class I got in and turned my truck on but everything on the dash and even the AC control started flashing. I turned it off and tried to restart but the alarm went off when I tried again. After unplugging the horns so I could trouble shoot in quiet I tried to turn it over again but it wouldn't. After hooking up battery cables to a buddies truck, I tried to turn it over after maybe 10 seconds of being hooked up and it started and ran like normal. But after getting home I turned it off and tried to start her up again and nothing.

I'm starting to believe the noise may have actually been my alternator and not the transmission? The battery is less than a year old and hasn't given me and problems since I got it. Does anyone have any ideas or solutions?

Again I really appreciate any help I could get!

 

check your battery voltage, if your alternator goes out it runs the battery dead regardless of how old your battery is. Id get both checked at local parts store.