Our group showed that congenitally profoundly deaf infants also have “babbling”, or transitional mumbling, which is a vocal activity that is not subject to auditory feedback; and that early intervention in deaf infants during the first 8 months of life can lead to better speech development. The results of this study were obtained by comparing the characteristics of pre-speech speech development of normal and congenitally profoundly deaf infants with the characteristics of their cognitive development associated with speech development. The study divided the congenitally severely deaf infants into a deaf A group (hearing aids started before 8 months of age) and a deaf B group (hearing aids started after 8 months of age13), with normal infants as the control group, and conducted long-term continuous audio and video recording and observation, as well as vocal spectrum analysis of their vocalizations. The results showed that babbling (mumbling) was divided into transitional mumbling (/a-a-a-/, /a-u-u-/, / e-e-e-/) and standard mumbling (/ma ma ma/, /ba ba ba/, /da da da da/). There was no significant difference between the normal group and the deaf group for transitional murmurs at the beginning of speech development; whereas the emergence of standard murmurs averaged about 8 months for the normal group, about 6 months for the deaf A group, and about 13 months for the deaf B group. These results suggest that the transitional murmur stage of speech development, in which vocalization is independent of auditory feedback, and the subsequent development of standard murmur and meaningful language, are both influenced by auditory feedback. Therefore, when discussing the early detection of deaf children, it is necessary to reconceptualize the relationship between deafness and babbling (mumbling), and to clarify the classification of babbling. In response to the current phenomenon that some health care providers or physicians refuse to perform audiological examinations on infants and children suspected of having deafness on the grounds that “the child is babbling, so there is no hearing problem” and thus delay the diagnosis, this study reminds physicians and parents that when a child is suspected of having hearing problems, regardless of the presence or absence of mumbling, they should actively perform This study reminds doctors and parents that when a child is suspected of having a hearing problem, regardless of the presence of mumbling, a rigorous audiological examination and audiological evaluation should be performed to rule out the possibility of hearing impairment in a timely manner. The results of this study provide a scientific basis for the early detection, early diagnosis and early education of deaf children currently being carried out.