# A Preliminary Study of Model-Generated Speech
## 5 Discussion
### Different Mechanism for the Sounds Generated by the Models and for Those Acquired by Human Beings  
[15] claims that \"the relative chronological order of development remains everywhere and at all times the same\". This means that the pace of development in children may vary, but the order in which the sounds are acquired seems universal. Our study reveals a general pattern for the order in which sounds emerge in children: stops are acquired before affricates, and velars are acquired later, while level tones are acquired earlier than contour tones. However, the sounds correctly generated by the three models display approximately the opposite relationship. Ref. [15] also claims that \"only those sounds which are common to all the languages of the world, while those phonemes which distinguish the mother tongue from the other languages of the world appear only later\". He also suggests that identical laws operate in the phonological development of language in children and the synchronic structure of the world's languages. As such, unmarked sounds are acquired earlier than marked sounds since unmarked sounds appear in most languages of the world, and the acquisition of some sounds presupposes the acquisition of other sounds. [PERSON]. [15] also provides evidence to show the mirror image of the developmental sequence of language acquisition in the study of aphasia, which is, to some degree, in line with our model-generated sounds. In this sense, we would further argue that model-generated sounds are determined by the sequence of word combinations from left to right. Only the onsets generated by the models present a mirror image of the sequence of children's language acquisition because the phonotactic constraints of word combinations restrict their appearance. The more common this onset is, the more variety is found in its following unit, which is either a glide or a vowel. This means that the more unmarked the onset, the better the chance/probability that it can be preceded by other units. If this is the case, it shows why the prediction achieved by our model is less accurate, resulting in lower accuracy in relation to onset production. At first glance, hearing-impaired children seem to be affected by their physiological disorder, for example, with reduced ability to hear high-frequency sounds such as stops. However, Ref. [40] found that the English allophone \(\left[z\right]\) may have three different meanings when combined with other morphemes. Take the word \"cook\" as an example, where \begin{table}
\begin{tabular}{l l l l l} \hline \hline
**Tone Contour** & **Model\_acc** & **Rank** & **Distribution** & **Rank** \\ \hline Level tone (T1 (33)+ T5 (55)+ T7 (11)) & 57\% & 1 & 45\% & 1 \\ \hline Contour tone (T2 (52)+ T3 (213)+ T6 (35)) & 55\% & 2 & 38\% & 2 \\ \hline \hline \end{tabular}  
* Tone register
* H initial T value (T2 (52)+ T5 (55)+T8 (4)) & 65\% & 1 & 42\% & 1 \\ \hline L initial T value (T3 (213)+ T7 (11)+T4 (2)) & 50\% & 2 & 27\% & 2 \\ \hline \hline \end{tabular}
* Tone duration
* Unchecked tone (T1 (33)+ T2 (52)+ T3 (213)+T5 (55)+ T6 (35)+ T7 (11)) & 57\% & 2 & 84\% & 1 \\ \hline \hline \end{tabular}  
* 64\% & 1 & 16\% & 2 \\ \hline \hline \end{tabular}  
\end{table} 
Table 10: Comparison between tone accuracy for tone contour, register, and duration, generated by the models and tone distribution. (a) 'cooks' is the plural form, (b) 'cook's hat' is the possessive case, and (c)'mummy cooks' is the inflectional form of the verb, 'cook'. The acquisition sequence in children goes from (a) to (c). In the case of a patient with aphasia, the sequence of loss was as follows: first, the suffix of the verb, (c), then the suffix of the possessive, (b), and finally, the suffix of the plural noun, (a). The order of aphasic loss went from the sentence level (c) to the phrasal level (b) and then the word level (a), i.e., from the most complex form to a simple form. The results generated by the three models, to some degree, reveal a similar phenomenon.