# Do We Get What We Need from Clinical Acoustic Voice Measurements?
## 2 Background: Current State of the Art and Challenges in Clinical Acoustic Measurements
### Dysphonia and Acoustic Measurements Depend on the Token and Elicitation Task  
Dysphonia has primarily been a concept of how a voice is perceived against an internal standard of \"normal\". In clinical application, standardized assessment schemes such as the Grading-Roughness-Breathiness-Asthenia-Strain (GRBAS) scale or the CAPE-V protocol have been recommended to focus on specific characteristics. However, even with standardized scales, there will be variance in judgments due to differences in training or the cultural background of the examiner [29; 30]. Thus, an instrumental acoustic measurement of dysphonia seems to be a logical solution for an objective assessment of voice dysfunction.  
However, there are some observations that may challenge the idea of capturing \"dysphonia\" per se. First, humans may weight and integrate information about aberrant voice function differently as single and combined acoustic indices [30; 31; 32]. Moreover, when human assessment is based on cultural and mental concepts, how do we compare this information to objective measures? In recent years, considerable effort has been invested into establishing language-specific normative values for CPP and the combined indices AVQI and CSID [23; 28; 33; 34]. However, if we use language-specific normative values, this may undermine the comparability and transferability of study results between languages. Especially when native speakers assess the voice samples, there may be substantial underlying differences in perceptual expectation and training [31]. From a technical viewpoint, some phonemes, such as the fricatives /f/, /s/, or /sch/, can act as additive noise in speech samples. Depending on the applied parameter, this may inflate assessment results and, thus, the impression of pathology, when these phonemes are more frequent in a language. These issues may be addressed by analyzing only vowels; however, this leads to the clinical problem of the ecological validity of the token. Several studies have shown differences for jitter, shimmer, and CPPS in sustained vowel phonation as compared to speech, reading, or counting tasks [35; 36; 37; 33; 38]. Moreover, voice patients may perform well in one voice task in terms of voice technique, and sound much more dysphonic in another. Thus, a global representativity of a normative value or token cannot simply be assumed.  
This calls for a standardization of tokens across languages, including standardization of vowel phonation and description of the phonetic context for speech and text. Moreover, a widespread data base is needed to understand what is comparable between languagesand what is language- (and culture-) specific in voice acoustics. In a clinical setting, we also need to consider what patients are able to perform, and under which conditions their voice problems will be most measurable. This calls for a disease- and function-specific assessment approach. For example, in cases of neurological pathology, investigation of alternated motion rate (AMR), or use of acoustic parameters such as voice onset time (VOT) and space vowel area, were recommended for the acoustic analysis protocol [9]. Furthermore, specific populations, such as professional voice users, may need the exploration of endurance task or extended VRPs. Further research is needed into adequate language-neutral and language-specific tokens considering the pathology and the specific population.