I've seen this graph:
But I don't get something. Consider the 2kHz line (highlighted in red).
This graph implies we can hear an orchestral instrument at 2kHz before we can hear a human at the same frequency? But why is that? I would assume we're considering the same amplitude of source, so it doesn't seem like that's the cause.
So if they're the same amplitude and same frequency, they must be the same wave then. Thus how can they be perceived differently?
What's so special about musical instruments that makes them able to be heard earlier?