Audiologist tell us that a 10 fold increase in sound pressure leads to approximately a 2 fold change in perceived sound intensity. Add to that the fact that the bell scale is logarithmic- 120 ==> 140 dB is a 100 fold increase in sound pressure, but only about a 4 fold increase in perceived sound…
But, the question wasn’t about hearing damage, it was why do people say the TC sounds quieter than it meters. The answer is because sound is perception and everyone is a bit different.
I, for example, have tinnitus (not from loud sound exposure) and high frequencies blend into the ringing I hear all day every day.
Teenagers have much better high frequency response than older adults, and some inventors have used this fact to develop audio hazing devices that emit a high frequency whine. Loud enough to be annoying, high frequency enough not to be heard by most adults. But, designed and marketed to dissuade teenagers from loitering where they are not wanted to congregate.
Yes, a “loud” can with a “pleasing tone” will damage your hearing. And, is arguably worse than a loud can with an obnoxious tone- as one may be less inclined to wear hearing protection if the can “sounds good.” But, that still wasn’t the question.