I've noticed that certain bass and baritone register sounds often seem sharp to me, even when they are ostensibly in tune- the notes are checked with a tuner or generated by a digital synth that won't go out of tune. I've also noticed that some sounds seem to go even sharper at high volumes. What is causing this discrepancy between perceived pitch and the "actual" pitch of the instrument?
I've read unsourced claims that at high volumes, high frequencies sound sharper and low frequencies sound flatter. I haven't found good reputable or detailed sources for this.
I was reminded of this phenomenon by this question.