I recently discovered a website where you can buy old time radio programs. The site is called, not surprisingly, Old Time Radio Catalog. Among their many programs I noticed they had a Ronald Knox Collection which included: Ronald Knox on the Birth of Our Lord, Ronald Knox on the Conversion of Newman, Recollections of Chesterton, and, my favorite, Ronald Knox on Translating the Bible. The last one is available in printed form from Baronius Press, where it is included in the collection of essays that accompany the Knox Bible. All four programs are relatively short, totaling about an hour and a half. The disc is in MP3 format which is nice. There is a sample on the page from Knox for you to listen to as well.
I really enjoy having these recordings. It gives a special added delight when reading a particular author having actually heard their real voice. I do that often when I am reading works by contemporary authors like NT Wright or Peter Kreeft. The same joy I had of hearing Msgr. Knox's voice was rivaled only when I heard the distinctive voice of C.S. Lewis. So, I highly recommend this collection. It is only $5.00 with a few bucks additional for shipping. They sell other Catholic and Protestant recordings as well.