## 3 Materials and Methods
### Procedure  
The questions in this interview were divided into four parts. The first part includes some basic information of deaf college students and teachers. The second part involves the discussions about the classroom interaction and communication of deaf college students in the multimedia-equipped classroom, with its purpose to explore in depth what the classroom interaction and communication problems are about, how the problems come into being, and what the current solutions are. The third part is about supplementary questions, aiming to understand whether the communication problems they have in class will affect their learning and processing after class. The last part provides some open questions to supplement the aspects ignored during the interview, to have a more comprehensive understanding of the problems of deaf college students in classroom communication. After transcribing, the research applies qualitative-analysis research methods with the help of NVivo11 qualitative-analysis software, analyzes the transcribed interview text word by word and completes the three-level coding, thus building a basic framework for analyzing the in-depth needs of deaf college students in classroom communication. In the qualitative research, coding is the process of redefining the contents of data, and classifying, summarizing, and interpreting the data of each part at the same time. Through the method of extracting information vocabulary, it is the key link between collecting data and forming the theory of interpreting data [30]. Firstly, the sentences related to the topic are screened and extracted, given their concepts, and encoded at the first level in NVivo11 software. These concepts are classified and summarized to form different genera and establish nodes. At this stage, 37 generic categories were established. For example, some students said: 'I could not fully understand the questions or the teacher's words during the interaction when the teacher was using hand gestures. I sometimes think that I understand, but I am wrong when the teacher writes on the blackboard. I realized I had misunderstood'. However, some students said: 'I think some students do not understand the teacher's question because of different understanding ability. I think there are many mistakes in understanding writing words. It is better to use gesture language because writing words will be very troublesome.' Such content is classified as the individual ability to understand. Therefore, we classify these two parts of the interview content as having different understanding accuracy. Secondly, the relevance among 37 categories in the primary code is mined through the secondary code, and seven tree nodes are established in NVivo11; that is, seven main categories are established, which are the accuracy of understanding the lecture, the efficiency of understanding, the richness of interactive communication, in class records, after class records, the willingness of teachers and students to interact, and the assistance of interaction. Finally, through the induction and summary of the seven main categories three core categories are created, namely three core nodes: the diversity of explanation, the recordable contents, and teacher-student interaction. The three-level coding process is shown in Table 1.  
Figure 1 shows a hierarchy diagram generated by NVivo11 to clarify the hierarchical status of each node in the coding system. The frequency and percentage of each core node in the subjects' views are shown in Table 1: among the three influencing factors, the subjects believe that the most relevant factor to classroom interaction is the diversity of lectures, with 84 reference points, accounting for 43.3%; then, the contents can be recorded, with 72 reference points, accounting for 37.1%; the last is teacher-student interaction, with 38 reference points, accounting for 19.6%.