Wellclined

A small device or app for sale

Plugs into home phone lines, in line with the telephone. Much like a fax line did, this device would record the first 10 seconds of each inbound telephone call and compare it to the last 100 calls received. This could also be done in form of a software on the server side as a app. An automated recording (inbound Robocall) would leave a sound footprint that could be compared even if female voices would be replaced with male voices. No matter where the call originated from. Every robocall recording would only be able to call a few homes until it has triggered the networked database.
A data center could keep caller ID data and voice footprints as a data block as well as time of incoming calls and your phone number (for tracing purposes). Such a device could get updates or even load confirmed voice prints into a national data center via phone lines even share those voice prints with all other devices through a national data center. After multiple reports of such phone calls by multiple users, robo calls could be closely monitored on a national switchboard level and filtered out. Realistically most of our phone lines are not used most of the time so a upload speed would not be that important and plenty of down time during calls allows for updating via phone lines.
Some exceptions such as collect calls would have to be written into the voice detection as well possibly with a numeric data key or an exception such as caller ID like 911 calls.
A voice mail could also be a second option with a ten second delay to actually ring the home phone to play a friendly message and trigger the robocall.

If the call would make it through the voice detection first 10 sec. of all incoming calls. The home owner would also have an option of manually adding the caller into the block list with a key pad combo.

if a robocall is detected manually or by voiceprint a timestamp and call time as well as the phonenumber that received the call would be submitted for tracking analyses. this would render a IP address and force the voice over IP caller to change its IP number. Most important is however that the voiceprint has been recorded and is now in the block list inside the data server. This voiceprint would have to be altered to not trigger the "wellclined device or app" however if it is reported manually or automatically in its "new altered form" more than 15 times as example it would be added to the list again and blocked by all users even those that never received that specific robo call.