On: InCall Advertising - A Startup Idea

I don't understand what you're saying. This is supposed to be a plan that you get. Basically you choose it, and then get a free call or lower cost. You have noises in the background anyways. Blurring them with something better isn't really disrupting the call?

This smacks of subliminal advertising, it's not 'done', possibly even illegal, it certainly is in film and television advertising.

There are two sides to a phone call, a caller and a called person, afaik they both hear the same sound.

Advertising is by default subliminal.

Not necessarily true. Example: when your credit is about to expire, you get a notification that the other side won't hear. Two sides in a call can hear two different sounds.