I think part of the problem with a ticking clock is when you are not used to it!

When we are around the same sounds all the time we begin to 'ignore' them consciously. The brain's filtering system realises that the sound is not important to our conscious awareness and simply filters it out.

I moved into a house with a grandfather clock just outside my room which struck on the hour, the number of hours that the time was. Needless to say, for the first week or so I constantly woke... especially at 12.00 with 12 chimes!! Very soon however I was able to 'sleep like a baby' and did not ever notice it!

I think you have done the right thing though to have a clock with a soft tick, then it wont drive you up the wall when you are up at all hours!