There was a post not too long ago discussing boobs and how people react to them. One of the responses was from a foreign aid worker in Haiti after the earthquake. In Haiti, it's not uncommon for women to walk around with uncovered breasts. At first, the poster said, they found it extremely distracting, because boobs were everywhere. After a few days uncovered boobs stopped being novel and sexy, because they were everywhere.
Once their assignment in Haiti ended and they returned to their home country, boobs started being sexy again... all that to say that while they are a secondary sexual characteristic, it is a cultural construction whether or not they are seen as overtly sexual.
It's true. I've stopped using sounds and songs that I enjoy as my alarm because of this. I haven't used an actual alarm clock in years, but the sound of a circa-2000 electric alarm clock buzzer going off instantly activates my fight or flight mode.