Interpreting audiogram BC symbols < [


Sometimes I find myself confused looking hand filled audiograms.

Some audiograms plot bone conduction symbols < > and [ ] in the middle, see the red arrows.
I’m curious finding what does this means? Do they belong to 500 Hz or 1000hz?

  • Image from Google, not mine

Usual audiograms have the symbols right away on the frequency line, like this, and I understand it.

I would appreciate if somebody help me to understand this.


By elimination, they go “on top of” the AC marks, but were drawn a little to one side for clarity. And I see they are drawn “outside the head”: the right BC is a little to our left of the AC mark, the left BC is a bit to our right of the left AC mark.

Testing is usually AC first… we hear through air. “Can you hear me now?” If that is not excellent, then put the tuning-fork on the temple “can you hear this?” If there is no earwax, puncture, swelling etc, the BC will plot on top of the AC, so the tester has to cheat it over a bit.

It sure also helps if you have two graphs, one for each ear. However it is generally best to plot BC on same graph as AC because the -difference- suggests external problems which might be fixed with a scraper or hot vinegar or knife or antibiotics. Melvyn-42


Thank you @Zebras
I understand the meaning of each symbol. I can’t understand where it belongs when it’s located in the middle, as indicated by the arrows in the OP.

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My take is that they put them to the side to show that they were equal. They test them both at the same frequency. Ideally, if they were equal they would be superimposed, but that tends to be messy.