# Influence of the Sound Source's Position on the Stage on the Speech Perception in the Auditorium
###### Abstract  
Constant efforts to achieve the best possible speech intelligibility during theatre performances were the motivation for the research presented in this article. The acoustic conditions in a theatre hall depend not only on the design of the room acoustics, but also on the stage decoration and the positioning of the sound source (actor) on stage. The ACR (Absolute Category Rating) method recommended by the ITU was used to investigate the influence of the decorations and the position of the speaker on stage on the subjective evaluation of the listeners' perception of speech. Subjective tests were carried out in situ and in the laboratory based on recordings made in the facility that was the subject of the measurements. An extensive analysis of the results was carried out, taking into account individual aspects of the tests, such as the type of decoration, speaker position, listener position, and the way the recording was made. Based on the discussion of the results, the conclusions are presented.  
speech perception; speech quality assessment; stage; auditorium; speech intelligibility; stage decoration +
Footnote †: journal: Applied sciences  
Numerous works on room acoustics have addressed the subjective perception of speech or music [13; 14; 15; 16; 17; 18; 19; 20]. The results of this work indicate that this is a very important issue that should be investigated in theatre rooms for speech as well as music perception.  
In verbal communication, it is not only the intelligibility of speech that is important, but also its quality, in terms of the listener's feelings. Speech quality can be assessed by subjective or objective methods [21; 22; 23]. In the present study, speech quality assessment was performed by subjective methods, which are still the only verifier of the effectiveness of objective methods. Of the many different subjective methods for assessing speech quality [24; 25; 26; 27; 28; 29; 30], the Absolute Category Rating method recommended by the International Telecommunication Union [30] was used in the study. Objective methods for assessing speech quality are still an unfulfilled hope for eliminating costly, labour-intensive, and highly skilled subjective methods. In room acoustics and the evaluation of public address systems, the Speech Transmission Index (STI) is most often used as an objective measure [31; 32; 33; 34; 35; 36; 37].  
The presented research aimed to verify how the following staging elements influence the quality of speech perception:  
* change of scenography;
* the position of the speech source on the stage.  
Sometimes it is not possible to carry out measurements in situ, e.g., due to the inability to assemble a listening team at a specific time. For this reason, it was additionally decided to record the test material in the test position in the auditorium and then perform the speech quality measurements in the laboratory. This procedure was intended to test the compatibility of the results of the assessments made in situ and under laboratory conditions. In the case of measurements in the laboratory, the problem of recording the test material in the room being assessed arises. This is because there is the question of whether to record using an artificial head or a classic measurement microphone. In the present study, a comparison was made between the results of test material recorded using a microphone and an artificial head. The compatibility of the results in situ and in the laboratory considering both ways of recording the test material was investigated.