Drupal is pronounced as "Druppel" with 'D' as in 'D'o, 'ru' as in T'rue', 'ppe' as in 'Pe'n and 'l' as in Tel'l'.
In phonetic notation this is written as
The name originated from the dutch word 'druppel' which means 'drop' which again came from a typo when Dries Buytaert typed in drop.org instead of dorp.org for a domain for the CMS he had built. Dorp is the dutch for 'village'.
You can listen to Dries Buytaert, the founder and lead developer of the Drupal project, pronouncing Drupal below
You can read more about the history of Drupal at Drupal.org