Mac makes a ticking noise like a clock?

i have a macbook pro 2011 running snow leopard 10.6.7 and i keep hearing this noise like a clock every 5/6 minutes. but i have no idea what it is. I know it isn't hardware anyone have an idea? i don't have any apps open other then chrome and outlook. no clock or time keeping apps installed im really confused.Mac makes a ticking noise like a clock?
You say that you know it isn't hardware... Is it coming from your speakers then? If not...



Sounds like the fan to me. Probably is struggling due to dust build up. Get some compressed air and blow our the entire back vent. If it continues, it could be a defective bearing in the fan, causing an unbalanced rotation that causes the noise. The fan isn't always on, so that would explain the fact that it only happens sporadically.

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