I've owned and ridden a lot of different bikes. From a BSA, to Hondas, to Harleys, to the last 3 flavors of Indians. Everyone single one of them had their own particular engine noise. With pretty much any bike, you can even ride the same model and year and it will sound different.
The loudest bike I've owned is probably my BSA.. but I put straight pipes on it which solved that issue. Even my soul-less Hondas would make add noises at times.
Ok - not to get too technical, but from a design stand point (I was a Design Engineer in my past life), there is a thing you have to look for when doing your design that's called "tolerance buildup".
The engine on your motorcycle is made up of a lot of different parts. Each of those parts are specified to be made within a certain size or form tolerance. That tolerance is specified as + or - a certain distance. Depending on the part, this distance could be .002, .005, .010, or more. When those parts are made they come in somewhere within that range of tolerance. Tolerance buildup is the consideration of how all those different parts that are coming in as slightly different sizes will all work together. What will happen if all the parts come in at max tolerance, meaning they are all as large as they can be and still within tolerance? What will happen if all the parts come in at min tolerance, meaning all the parts are as small as they can be and still be within tolerance? What if some are max tolerance and others are min tolerance? All the various plus and minuses have to be considered.
Now consider the tolerances that exist within the assembly process. There are tolerances there too. There are tolerances on how the parts are positioned as well as the torque each fastener is installed with.
ALL of this creates a unique sound and feel to every engine made. Some of our engines will be louder and others will be quieter. It's likely though that all, or nearly all, of our engines are within specification. That unique sound you hear is the voice of your bike. Don't worry about it if that voice is different than other bikes you've had.
Remember also that we have warranties. For example the 2014's have a 5 year warranty, so if your engine happens to have been put together incorrectly (which is a VERY small percentage of all the bikes out there) Polaris / Indian will fix it. So what's the worst thing that can happen? You ride your bike for a while and the engine blows up... and then you get a brand new engine put in on their dime. Doesn't sound so bad to me.