If John is talking to Bill on the telephone, why can't John hear his voice being projected into Bill's bdroom?

Question

I was talking to my friend on the phone earlier, and she played a recording of our friend singing that she had recorded with her cell phone earlier that week. However, I could not hear any trace of the recording. Also, her phone was running low on battery, and it began to beep incessantly, and this I could not hear either. Then, I realized that if I were able to hear the sound produced by my friend's phone, I would also be able to hear my voice resonating around her kitchen, because I was on speaker-phone at that point. Why couldn't I hear the sounds being produced by the cell phone with which mine own was corresponding?

Answer 1

Probably the microphone on that cell phone is not particularly sensitive, or is moderately directional - probably designed that way in an (apparently successful!) effort to avoid having it pick up too much background noise. ;-)