# Auditory Perception of Impulsiveness and Tonality in Vocal Fry
###### Abstract
One effect of glottis constriction is that the closed glottal phase is long in comparison with the open glottal phase, which results in a small open quotient:  
\[\text{Qo}=\frac{\text{durationoftheopenphase}}{\text{cyclduration}} \tag{1}\]  
[PERSON] and [PERSON] found an open quotient of 0.25 to 0.45 for fry compared with 0.65 to 0.7 for modal voice, and 0.9 to 1 for breathy voice and falsetto [22]. Another effect of glottis constriction is that the vocal folds may close faster than they open. This causes an asymmetry of glottal area pulses, which is characterized by the pulse skewness:  
\[\text{Qs}=\frac{\text{durationoftheopeningphase}}{\text{durationoftheclosingphase}} \tag{2}\]  
According to [PERSON] and [PERSON], voice types sorted by decreasing of pulse skewness are vocal fry, modal, falsetto, and breathy voices [22]. In our study, we examine whether glottal pulse skewness has a measurable effect on perceived fry. In particular, increased skewness may be hypothesized to favor the perception of fry because it makes the voice source more transient. On the level of auditory perception, we define vocal fry as the temporal segregation of individual glottal pulses, meaning that individual glottal pulses are perceived separately. In the past, vocal fry and creak were treated as binary; that is, they were either present or absent [23; 24]. A possible reason is that perception is less sensitive to differences between items that are categorized together a priori [25]. However, in our study we examine whether a graduation between vocal fry and modal voice exists because our informal preliminary perceptual observations suggested so. To capture such a hypothetical gradualness, we let listeners rate perceived impulsiveness using a 7-point Likert scale to indicate the extent to which individual glottal pulses segregate temporally. At one end of the scale, the individual glottal pulses cause distinct auditory events that a listener can count, while on the other end of the scale the individual pulses merge temporally, forming a continuous percept. We hypothesize that perceived impulsiveness is a proxy for binary fry, which may be more informative than the binary label since it involves a finer grid. [PERSON] previously stated that at least three degrees of perceptual prominence of most phonatory settings may be distinguished, specifically, slight, moderate, and extreme degrees [6]. This may also apply to vocal fry. Such distinctions may become more relevant for future linguistic studies in the long run, since one may hypothesize that speakers and listeners may decode and encode para-linguistic information in these graduations. Pitch strength is the perceptual attribute that reflects how strong (distinct) as opposed to faint the pitch of a sound is perceived [26]. Informal preliminary perceptual observations suggested that pitch strength varies when voice quality transits from modal voice to fry or vice versa. In particular, pitch strength appeared to be larger in modal voice than in fry. In this study, we test the contribution of pitch strength to perceived fry using a 7-point Likert scale. The term tonality is used as a synonym of the term pitch strength. A related term is pitch salience, which relates to the pitches elicited by individual components of a sound; the assessment of this factor is beyond the scope of this article [27]. A topic that is currently underinvestigated concerns the internal auditory reference standards of vocal fry. What makes this topic important is that the variability of these standards results in inter- and intra-listener variability in detecting fry. We expect to find substantial differences in reference standards between individual listeners. We assume that these differences may be decreased by anchoring, and that they may be influenced by the short-term segmental context (i.e., the within-vowel co-occurrence of fry and modal voice). Understanding the relevance of anchoring may improve the reliability of perceptual voice assessment in the future.