Motorbikes and birds, oh my!

I was showing/explaining my audiogram to my John. My worst loss is around 4-6000hz, where the picture of the motorbike is on the audiogram background I 'borrowed' from google. It's my first post if you want to look at it. There's also a picture of a budgie at the top of the same hz level.

Now, unaided I can hear motorbikes, and birds (lots of other things too, but I'm just talking about those atm). My evil ex had a budgie and it sounded very loud- I could hear it upstairs with the door shut. Birds sound like cheeep cheeep cheep, ranging from just audible to oww not so loud! and motorbikes sound like vrooooooooooooooomgrrrrrrrrrahvroooooom, very loudly. Ear hurty loudly. This led to a puzzle I can't solve- either birds round here are very loud or I'm misunderstand the audiogram? John pointed out that motorbikes sound LOW to me cos I can't hear the high tones as well as others, but I thought why are they in the wrong place on the chart?? Even aided they go vroomgrrrrr...he said it depends on the engine, some are higher than others.

Any thoughts? Anyone? Bueller....?