According to the GfK MRI Fall 2016 Survey of the American Consumer®, cell-phone only households make up 52% of households. Its even up to 23% for people aged 65+, which is the age group most likely to still have a land-line. Among the Millennials, cell-phone only households are up to 71%. This means that any phone survey is going to have to include cell phones, or it is probably not a valid sample.
According to the Pew Research Center’s State of the Media Report for 2016, 21% of respondents said they had listened to a podcast in the past month. That’s up from 17% in 2015, and was only 12% in 2013. Listening is also moving over towards mobile – they say 65% of those who listen to podcasts say they most often do it on a mobile device. (Makes sense – almost all of my listening is during walks or while driving.) Only about half of the respondents were familiar with the term “podcast” so there is still lots of room for audience growth.
The amount of time listening to podcasts make up only 2% of the time spent consuming audio – compared to 54% of the time spent listening to AM/FM radio.
There are more details at http://www.journalism.org/2016/06/15/podcasting-fact-sheet/.