Whine while accelerating

Just started hearing this whine yesterday, so my first thought was to post something on here before taking it to the shop. The whine sounds almost like a golf cart accelerating. Attaching a video of it. It can be heard through third gear as long as the radio is turned off but is very faint, almost inaudible, from fourth to sixth gear.
A little about my truck: 05 TRD Off-Road, 6-speed manual trans, 150k+, original owner, any further questions, shoot them my way.

 

Mine does it in fourth gear, 2014 TRD Off-Road, six speed manual.

It's done it since I got it with less than 12,000 miles on it.

I would recommend changing out the fluid and putting in some Redline MT. Maybe your transmission fluid is getting a little worn out.