Hello,

The main difference between children and adult speech is the fundamental frequency response. For children, they have shorter vocal track and smaller vocal fold. That is why children utterance have higher fundamental frequency than adults. 

Thanks for your explanation, yes i believe that it is one case which they are different from each other. It would be great if you could please provide me references for your answer.

Saeid,

I am attaching a link with a summary about children language acquisition from Linguist List where you may find some useful information about their linguistic, cognitive and phonetic skills.

http://linguistlist.org/ask-ling/lang-acq.cfm

Thank you very much Olga.

The main difference relates to the prosody which is composed of the fundamental frequency, the intensity and duration. In our current research effort we are also investigating the rhythm metrics.  Rhythm is defined as the perception of regular

prominent units in speech. Speech rhythm is also related to an individual’s

perception of speech and of differences between languages, language varieties

and individual speakers. During infancy, the identification of words and syllables is mainly achieved by rhythm through prosodic features.

Here, I have attached a paper. I hope this will help you. Thanks.

Thanks Sujan, It actually is helpful.

On the linguistics side, I would say that some papers have defended that children are more limited than adults. Not many papers have tried to make direct comparisons of children and adults' productivity controlling for syntax and lexical knowledge. You may have a look at my thesis. 

Article The acquisition of morpho-syntax in Spanish: Implications fo...

Thanks a lot for sharing your thesis. I will read the relevant chapters and get back to you.

One difference is that the children's grammar is more restricted, see for example about the verb system: Development of Verb Inflection in First Language Acquisition: A Cross-linguistic Perspective, ed. by Dagmar Bittner, Wolfgang U. Dressler, Marianne Kilani-Schoch (Walter de Gruyter, 2003)

Thanks. I will try to find the copy of the proposed paper.

I am sure I am not telling you anything you already do not know.  Speech awareness and production change as the childs aerodigestive tract and articulatory structures  grow neurologically and physically. The more complex articulatory motions develop in skill last.  That is why so many SLPs in the school sytem are working on remediating pronunciatieon of /s/ /r/ /l/ and why the general population still does not accurately pronounce /z/ at the end of words. Children living in the  Midwest United States in Kindergarten and first grade  are not fully expected to have mastered  /r/ produciton. Competence goes in grossly predictable patterns. (/m n ng  p f h w/, /b d g k r/, /t th L v/, /sh ch dg/)  In addition illness of childhood compromise pronunciation.  We have a life style that aggrigavates sinus mucosa and so velar valving for non/nasal produciton is frequently a contrast between the young and old (the older population have less of a problem with this).   The same problems are agrivating eustation tube function so middle ear problems and hearing of low frequency sounds is often poor in the younger population.  Confusion of sounds is common. 

Gross Linguistic factors have to do with onset of various linguistic development of referrent (word appoximations) based on frequency of useage, contrast of nasal and stops, starting with higly visible-labilal sounds (eg:mama, papa, baw/ball), gross differnetiation of place/manner/ voicing( gawgy.doggy), simplificaiton of articulation (Is/Its),

semantic (phrase) development and

syntactic development with semantic markers of plural /s,z/; gerund/ infinitive marking (-er), verb modifier (ly).  Early errors will occur due to the complexity of the linguistical formulation the child is attempting or the communicaiton load put upon them. (eg: my son's use of CRACKIE: confusing COOKIE and CRACKER. thinger/finger) and early onset  dysfluency .

I am sure their are early education, preschool, and school therapist who can amplify this explination if not to give you better examples..

Adults of various(and varying from sinus porblems) skill levels may  have difficulty with polysyllabic coarticulation/sequencing, maintaining voicing/developing enough intra oral pressure for voicing and so symplify or revert to poorly learned patterns and phoneme sequences (Black dialect has formatlized one of theses into using AX/Ask.  This also occurs in simplification or undershoot in pronunciation of blends like [n/-nd], sibilants [s/-sts], or voiced sibilants s/-z, -sh/-ch.

The low income population can have missing teeth or low grade pain that distract oral feedback of pronunciation.

Persons with GERD may have a loss of molars and restricted breathing from abdominal pain. Any recent change to the articulators will have an immediate though usually temporary affect on pronunciation. Just think of the last time you had novocaine at the dentist office.

The elderly have problems not so much from hearing loss (bone conduction for auditory feedback is often better than the acoustic signals for conductive loss -low frequency sounds, likley equvialent for high frequncy sounds -sibilants fricatives, affricates).  The more frequent problem is from poorly fitting dentures. Articulatory accuracy suffers especially for sibilants that require a fine airstream to be broken against the teeth. Also range of motion and rapid articulatory motion are hampered by a restricted tongue that is using the lateral tongue often to hold the dentition in place. The least thought of is .. age or illness related muscle weakness (sarcopenia) waisting most profoundly found in bedbound elderly.  Muscle wasting can occur after 4 days of inactivity./ in bed especaily orally with oral -throat soreness from cancer treatment on alternate feeding.

MikeC-SLP