A Scoping Literature Review of Relative Fundamental Frequency (RFF) in Individuals with and without Voice Disorders

Abstract

Relative fundamental frequency (RFF) is an acoustic measure that characterizes changes in voice fundamental frequency during voicing transitions. Despite showing promise as an indicator of vocal disorder and laryngeal muscle tension, the clinical adoption of RFF remains challenging, partly due to a lack of research integration. As such, this review sought to provide summative information and highlight next steps for the clinical implementation of RFF. A systematic literature search was completed across 5 databases, yielding 37 articles that met inclusion criteria. Studies most often included adults with and without tension-based voice disorders (e.g., muscle tension dysphonia), though patient and control groups were directly compared in only 32% of studies. Only 11% of studies tracked therapeutic progress, making it difficult to understand how RFF can be used as a clinical outcome. Specifically, there is evidence to support within-person RFF tracking as a clinical outcome, but more research is needed to understand how RFF correlates to auditory-perceptual ratings (strain, effort, and overall severity of dysphonia) both before and after therapeutic interventions. Finally, a marked increase in the use of automated estimation methods was noted since 2016, yet there remains a critical need for a universally available algorithm to support widespread clinical adoption.

Relative Fundamental Frequency: Only for Hyperfunctional Voices? A Pilot Study

“…In the same scoping review [21], the results obtained for offset cycle 10 in patients with vocal disorders were lower than those in healthy individuals. The RFF has been studied in patients with spasmodic dysphonia [29], Parkinson's disease [18], and VH with and without phonotraumatic lesions [2,17,28].…”

“…Roy et al [28] found values between 2 and 3 ST for onset cycle 1 in controls from their sample, which they compared with patients with MTD. In the scoping review mentioned previously, they concluded that onset cycle 1 values ranged from 1.68 to 3.82 ST, with a median value of 2.60 ST [21].…”

“…In a scoping review conducted on RFF, they concluded that out of the 14 studies performed with healthy voices to date (2022), offset cycle 10 values ranged from −1.10 to 0.05 ST with a median value of −0.6 ST [21]. The mean of cycle 10 of the control group in our sample is −0.9 ST (SD 0.59), which is consistent with what has been found in the literature to date.…”

“…It was speculated that the lack of increased tension from increased baseline tension would result in more negative RFF values in the final vocalization cycles compared to adults with normal voices, where values are around 0 ST. In patients with VH -including both phonotraumatic lesions and non-phonotraumatic subgroups, offset cycle 10 ranged from −1.76 ST to −0.80 ST, with a median value of −1.35 ST [21].…”

Pareto-Optimized AVQI Assessment of Dysphonia: A Clinical Trial Using Various Smartphones

“…A series of voice analysis tools includes many components to evaluate speech functions and voice quality [1,2]. The quantitative evaluation of voice quality using acoustics is advocated [3], and two metrics in this sector are the Acoustic Voice Quality Index (AVQI) and the Acoustic Breathiness Index (ABI) [4].…”