It is true if you have decent enough hearing and you practice this practice long enough, you can hear the ash falling from a joss stick if you are being attentive enough to it. On the other hand, there's tricks the mind does with the senses, which you can profitably employ if you are, yeah, being mindful.
The human body appears to privilege certain senses over others. I suspect that's why everyone I see walking down the street while I'm driving is walking in time to the music I'm playing in my car, even though they don't hear it. (I suppose if I were more woo-ful I would attribute that effect to an underlying rhythm of the universe, but I also suspect this is a field fertile for YouTube-ery if it hasn't already been covered.)
I have mentioned that one of the things I have learned from Wing Chun Kuen (詠春券) is just how naturally tense everyone tends to be, especially me, especially when confronted by a someone with 8 or more inches and 100 lbs than I have. I have been working to try to be aware of how tense I am at a given moment, especially under high stress situations, such as running late for an appointment, or meeting deadlines at work.
I have found that, for example, when waiting at a red light, the experience of time really changes if I am preoccupied with doing something else mentally instead of focusing on how silly the light timing is (a wide variety of activities are not recommended for this.) In particular, if I focus the mind on practicing being relaxed, the time indeed goes quicker paradoxically.