threshold for audio to midi

I am wanting to generate a midi track from a recording of an ancient clock - the clock is a little irregular in its timing and I want to capture that. I drag the audio onto a midi track and a midi track is generated. But, I need to be able to set the threshold for  conversion as the clock mechanism is quite noisy so the automatic algorithm is capture too much noise as if it were the clock tick and so there are far too many notes being generated. Is there a method to set an amplitude threshold so that only the loudest sounds are converted and the noise does not trigger a midi event?
 
thanks, greg

You might try applying Melodyne to the audio track first.  There is a slider which lets you set the detection level.  After you get it the way you want, bounce the region effect to clip and then drag the clip into your midi track.

thanks for these replies - I will try those solutions. And remember to say which version I have next time :)