Things no longer work this way. Old skool modems took advantage of existing lines designed for voice, so the tones were somewhat audible. Now, it's pretty much an ethernet connection straight to your house (a gross over simplification), but modern connections to ISPs are no longer the same.
Underneath the Ethernet layer there is still an old skool layer of modulation over a copper wire (unless you have fibre to your premises or are on wireless).
It's not that far removed from the old 56k modems. The main difference is that VDSL uses multiple carriers at different frequencies, but each individual carrier bears some resemblance to a 56k modem. VDSL is basically 10000 old skool modems running in parallel. It's no coincidence that the VDSL tone spacing is about 4kHz, or the bandwidth of a phone line. Your "voice phone line" is just carrier #0.
Also VDSL uses some very sophisticated channel modelling, whereby it measures the coupling between your copper wire and all the other copper wires in a bundle of telephone wires and cancels the interference out. This allows it to send carriers down the wire at frequencies that were previously unusable. It's basically a beefed up version of the 56k training, taking advantage of today's computers running faster and being able to run a more complex channel model/estimator in real time.
As a whole the VDSL signal is mostly on ultrasonic carriers, but it would be possible to tune into one of the carriers and listen to it. (Interesting project anyone?)
But if they could make grandma marvel at the sound of two blackholes merging by transposing a faint gravitational wave to sound, I suppose we could amaze grandma by taking some kind of wavy view of the digital signal while someone load the picture of a cute girl's black hole.
