As others in the comments have already mentioned, Studio Six makes very nice Audio Tools (at least on iOS/Mac, not sure if they are also on Android). Their SMAART module is the cheapest way to get access to SMAART tools - which can be a thing in and of themselves. I use them to asses what's going on with live sound I occasionally mix. What's really nice is they calibrate fairly accurately to Apple hardware out of the box. More than accurate enough for my purposes.