Speech production the larynx that then is modified by the vocal tract into different vowels and consonants. However speech production can occur without the use of the lungs and glottis in alaryngeal speech by using the upper parts of the vocal tract. An example of such alaryngeal speech is Donald Duck talk. The vocal production of speech may be associated with the production of hand gestures that act to enhance the comprehensibility of what is being said. The development of speech production throughout an individual's life starts from an infant's first babble and is transformed into fully developed speech by the age
Complete Vocal Institute sounds or had problems with their voice. The work formed the basis for the techniques Complete Vocal Institute currently uses and Cathrine Sadolin has continued the voice research together with physicians and acousticians. Cathrine Sadolin has been invited to speak in the voice conferences in Europe and USA since 1996. In 2007, she started to collaborate with consultant ENT Surgeon Julian McGlashan from Nottingham University Hospital. Their first joint research study was published in February 2007 on auditive research, where speech therapists had to determine which voice modes was used by listening to song samples. After that they cooperated to