Hitler was amazingly guarded about his public image, and because of this, there is very little out there in terms of candid recordings. The one extant recording we have was made June 4, 1942, during a visit to Finland. Ostensibly, he was there to greet Mannerheim, the Finnish supreme commander, for the occasion of his 75th Birthday. In reality though, the purpose of the visit was to shore up Finnish support and assure them of continued Axis success against the Soviets. Barbarossa had been launched a year prior and of course had not delivered a knock-out blow as had been hoped for. The Finns were an important partner of Germany, putting pressure on the Northern front, especially near Leningrad, and there were fears (which of course would come true two years later), that flagging enthusiasm might result in Finland putting out signals for a separate peace.

The meeting was on Mannerheim's private train, with a presentation of the Great Golden Cross of the German Order of the Eagle and a private lunch. Following that, the two leaders - along with Field Marshal Keitel and Finnish State President Ryti - had a conference which lasted for an hour and a half, mostly taken up by Hitler's monologues. He impressed upon the Finns the danger of the Soviet Union and the necessity of the conflict, but gave them no real indication of upcoming military plans. While we don't have the entire meeting, a recording of the first segment survives. It made by the Finns without Hitler's knowledge, and as such lacks the same tone and style that he exhibited in his public statements. Thanks to the wonders of modern technology, here it is on YouTube with subtitles.

Kershaw, "Hitler 1936-1945"