Or, do you even hear them?
i hear them all the time in some shows. Usually, someone makes a unique sound, and you'll hear it repeated throughout the entire episode, on every episode. On the Red Green Show, I used to hear the same guy going "HEE HEE!" several times an episode, and on This Hour Has 22 Minutes, I'd hear the same woman going "HAAAAAH!", again, several times an episode.
Also, some canned laughter sounds like it was recorded in the '50s.
You are very good on details...
27 per tv show times 4 shows an average per day times 43 years? 1,695,000 give or take. :)
Quite a few, but more the classics on the European side. As for English sketches, I remember a few, like: