# Intelligibility and Listening Effort of Spanish Oesophageal Speech +
## 3 Experiment 1: Preliminary Word Error Rate and Listening Effort Measurements
### Materials and Methods
#### 3.1.2 Corpus and Stimuli  
The parallel data used for this task contained 100 phonetically-balanced sentences selected from a bigger corpus [33; 34]. The selection of sentences was performed with a greedy-algorithm-based tool called corpusCRT [35], with the criteria of maximised diphone coverage and a maximum of 15 words per sentence. We collected recordings of 32 OS speakers in an acoustically isolated room with a studio microphone (Neumann TLM 103). This database (AhoSLABI) is available in Supplementary Materials and in www.elra.info. HS samples were obtained from an online platform [36] and hence, were recorded in variable environments. However, some of them were recorded in the aforementioned acoustically isolated room, although with a different microphone. The number of speakers in the HS database keeps growing as it is an open online platform. There were 35 speakers in the HS database at the time of performing this experiment.  
These 100 sentences were chosen to be phonetically balanced to ensure maximum phonetic content variability. They were syntactically and semantically predictable, but had some proper nouns and many unusual words that are hard to guess. This is to be kept in mind while considering intelligibility measurements. Some examples of the sentences are the following: '?Que diferencia hay entre el caucho y la hevea? _What is the difference between rubber and hevea (specific name of rubber tree)?_, 'Unos dias de euforia y meses de atonia.' _A few days of euphoria and months of atony (weakness)_.  
Not all the data of these corpora were evaluated in this experiment. A subset of 6 speakers (OS speaker IDs: 01M3, 02M3, 04M3, 25F3 ; HS speaker IDs: 114, 207) and 30 sentences were used as our stimuli (Sentence list provided in Supplementary Materials). The criteria and the procedure for these choices are described next.  
OS speakers to be evaluated were chosen based on two criteria--proficiency and accessibility. Speakers who practised for at least two years after the laryngectomy qualified as proficient speakers. Additionally, an OS voice quality assessment tool [37] was used as a guide to assess proficiency. This tool was based on the factors used in the A4S scale of [38] such as speaking rate, regularity, etc. We also considered accessibility of speakers as a factor, because their willingness and availability to come for follow-up recordings are useful for future research. Based on these criteria, we chose 4 speakers, three male and one female, making it gender-inclusive (there are only 4 women in the whole database and only 2 of them fulfilled our criteria). The criteria for choosing healthy speakers was quality of recording as well as gender balance. One male and one female healthy speaker were chosen.  
We conducted a pilot listening test to check if our stimuli were suitable for the sentence transcription task. We played the stimuli to some pilot participants who were not familiar with the stimuli, and hence, not primed. They reported that some sentences were effortful to transcribe as they were too long to remember. Therefore, we decided to use a subset of shorter sentences (maximum 40 phonemes), extracted using the aforementioned CorpusCRT tool. The result was a phonetically balanced set of 30 sentences with 7 to 10 words in each.  
To sum up, we had 30 sentences from each of the 6 speakers (4 OS and 2 HS), a total of 180 stimuli. They were normalised to a common peak value (0.8) to achieve a homogeneous and comfortable level of loudness.