Donald Duck talk
Donald Duck talk, formally called buccal speech, is an alaryngeal form of vocalization which uses the inner cheek to produce sound rather than the larynx. The speech is most closely associated with the Disney cartoon character Donald Duck whose voice was created and performed by voice actor Clarence Nash, and by Tony Anselmo after Nash's death in 1985.
Nash discovered buccal speech while trying to mimic his pet goat Mary. In his days before Disney, Nash performed in vaudeville shows where he often spoke in his "nervous baby goat" voice. Later when he auditioned at Walt Disney Productions, Walt Disney interpreted Nash's voice as that of a duck, at which point the idea for Donald Duck came about. Buccal speech was also used by voice actor Red Coffee for the character Quacker in MGM cartoons, and by Jimmy Weldon for the character Yakky Doodle in Hanna-Barbera cartoons.
The distinctive sound of buccal speech and the widespread familiarity of Donald Duck have led to unrelated, but similarly distorted forms of modified speech being described as "Donald Duck talk", such as inhaling helium.
Buccal speech is created with one of the buccal or cheek sides of the vocal tract. Both the air chamber and the replacement glottis are formed between the cheek and upper jaw. Buccal speech is produced when a person creates an airbubble between the cheek and the jaw on one side and then uses muscular action to drive the air through a small gap between or behind the teeth into the mouth. The sound so produced makes a high rough sound. This then is articulated to make speech. The speech sounds made in this way are difficult to hear and have a raised pitch. The technique can be also be used to sing, and is usually acquired as a taught or self learnt skill and used for entertainment.
Speech made when breathing helium gas is often called Donald Duck talk. This gas mixture alters sound waves due to its low weight and density. This raises the resonating frequency of the vocal cords by an octave shift up. Such speech is unintelligible largely due to the upward pitch shift in speech formants. Intelligibility is an important communication problem in deep sea diving. The technological solution involves unscrambling by electronic transcoders.
- Donald Duck-like speech is described to occur after pseudobulbar dysarthria in which speech gains a high-pitched "strangulated" quality.
- Donald Duck speech effect is described (usually as an undesired phenomenon) in audio engineering when speech is time compressed, rate controlled, or accelerated.
- The term is sometimes also used to refer to the frequency-shifted speech from an improperly tuned single sideband modulation (SSB) radiotelephone receiver, or the (nearly unintelligible) sound of a SSB signal on a conventional amplitude modulation (AM) receiver. 
- A high pitched nasal voice resembling Donald Duck is sometimes noted in individuals with Prader-Willi syndrome.
- Esophageal speech
- Vocal extended technique
- Overtone singing
- Circular breathing
- Critters (film)
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- Donald Duck--What's My Line Clarence C. Nash can be seen in this 12 December 1954 episode making his Donald Duck talk briefly at 7.01-03, 7.18, and 7.20
- (Part 1/2)(Part 2/2) Interview with Tony Anselmo
- YouTube has many examples of amateurs doing buccal speech