NEW DEVELOPMENTS IN ACOUSTICS

I've discovered something about the main-floor bathroom at the office that probably isn't surprising to anyone: I can hear it when the phone rings on a floor above ours. It's not a phone that belongs to any person or department in my company; it has to be a phone from some other company that makes its home above us. I wonder why it is that I can hear a phone, but not, say, a voice? Aren't they roughly the same volume? Maybe there's something about the waveform of a phone ringing that pierces walls and reverberates inside tile better. I don't have all the answers, people, I just don't.