# Analysis of Phonetic Segments of Oesophageal Speech in People Following Total Laryngectomy
## 2 Material and Methods
### Methods  
During the research, speech samples from the laryngectomy patients and healthy people were analyzed. People who had had a laryngectomy were undergoing speech rehabilitation aimed at learning oesophageal speech. For this reason, adequate words spoken, which are included in the rehabilitation programme, were examined. All words were spoken in Polish. In addition, speech samples were also taken from healthy people--the same spoken words were tested. The features of physiological speech provided a model (reference point) for comparing the values of speech descriptors in people after a laryngectomy. Taking into account the linguistic characteristics of the Polish language and the process of speech rehabilitation, the research covered the following words (spoken in Polish) [6]: a barrel, a bread roll, an egg, a package. For this study, a set of scripts (a program) was written in the Octave environment (about 30 functions). The Octave environment is an alternative to Matlab but has the same capabilities and similar libraries. The use of this environment for speech analysis is one of the generally accepted research methods described in [12; 13; 14]. The functions created calculate indicator values or control the running of a specific function--e.g., changing a domain, loading a\".wav file for analysis, windowing signals, etc. The returned results are saved to various files, and from these files are created for the WEKA target (Figure 2). Of course, they take into account the configuration of the specific feature vector (treating the content of this feature vector as a set of descriptors). Each of the tested words has been divided into phonetic segments. In the case of the words \"beczka\" (eng. a barrel) and \"paczka\" (eng. a package), three phonetic segments were separated out. The words \"bulka\" (eng. a bread roll) and \"jajko\" (eng. an egg) were divided into two phonetic segments. The number of phonetic segments contained in these words is directly related to the features of the Polish language. Upon completion, four words from each person were used for the research. When segmenting the words (division into phonetic segments), ten samples (segments) were tested for each person. Each of them was tested independently. For speech signal analysis, the audio-physical characteristics (descriptors) must be extracted. The above segmentation of the words resulted from the features of the Polish language. Each phonetic segment of the tested word was independently parameterized by speech signal descriptors. The numerical values of the features obtained from each segment of the speech of the laryngectomized persons people were compared with the equivalents of words obtained from the healthy people. Table 1 presents the phonetic segments of the studied words. IPA notations for studied words:  
* paczka--/pafka/;
* jajko--/jaejkz/;
* beczka--/befska/;
* buIka--/buwka/. Figure 2: Diagram of experiments. The features of the physiological speech samples provided a baseline against which the features of oesophageal speech were compared. The recording of the speech samples took place at the Bydgoszcz Laryngectomy Association (city of Bydgoszcz, Poland). The recordings took place in a specially prepared room. An OMNITRONIC IM-1000 PRO condenser microphone was used for the recordings. All speech samples were recorded in WAV format with a sampling rate of 44,100 Hz and 16 bits/sample [11,15]. For the parameterization of the mentioned phonetic segments, widely used time- and frequency-domain descriptors were used. The Octave programming environment as well as the Praat and WaveSurfer computer programs were used to conduct the research. The WEKA package, with the classifiers implemented in it, was used to carry out the classification process. Figure 5: Time waveform of the word “bulka” (eng. a bread roll)—healthy man. Two phonetic segments are visible. Figure 6: Time waveform of the word “bulka” (eng. a bread roll)—laryngectomised man. Two phonetic segments are visible.