Image after Proctor, K., Scherer, R. C., & Perrine, B. (2024). “Vocal fry patterns while reading,” Journal of Voice, 38(4), 889–902. https://doi.org/10.1016/j.jvoice.2022.01.013

Vocal fry is a sound production with a low fundamental frequency, classified as being a unique register because the voice is heard as individual pulses rather than a continuous sound. In vocal fry, auditory perception of fundamental frequency is detected by the auditory system through the timing of neural impulses instead of a place along the cochlea (the place code theory). Because of this, pitch perception relies on the collective timing and firing rates of neurons in the auditory nerve (Cariani, 1999; Oxenham, 2023). For speech-like sounds, alternating sound pulses and sound gaps are perceived as neural impulses if they occur below about 70 Hz (Keidar et al., 1987). Thus, as the auditory signal travels from the cochlea to higher brain structures, it categorizes fundamental frequencies below about 70 Hz as distinct temporal events, not as a continuous signal.

The production of vocal fry is not dependent on a single mechanism of vocal fold vibration. Vocal fold tissues are lax and appear to be able to assume a variety of tissue modes of vibration, symmetric or asymmetric (Herbst & Elemans, 2025). While vocal fry as a register has been given the label M0 (mechanism zero; Roubeau et al., 2009), a unique mechanism has not been identified. There is little activation of the intrinsic laryngeal muscles other than the adductory muscles.

Vocal fry has not been associated with any specific, well-defined vocal pathology, beyond a possible tendency toward unnecessary hyperadduction during its production (Van Doren & Rose, 2025). Rather, it is considered a linguistically normal phonatory quality usually observed at the ends of phrases signaling to the listener that the phrase is about to end (Van Doren & Rose, 2025). In some linguistic circles, vocal fry has also been classified as a sub-dialect (Yuasa, 2010; Chambers, 2009). Vocal fry is not just a series of equally spaced acoustic transients at the glottis but may be produced with a wide range of low frequency patterns (Scherer, 1989; Proctor, Scherer & Perrine, 2022). Nonetheless, the pulses in vocal fry can appear as a symptom in various voice disorders. Because of this, current clinical perspectives on vocal fry are mixed: while some authors describe it as an aberrant or potentially pathological voice quality and report negative perceptual judgments of its use (Pointer, van Mersbergen, & Nanjundeswaran, 2025), others simply identify it as a variant of normal (Oliveira, Davidson, Holczer, et al., 2015; Abdelli-Beruh, Wolk, & Slavin, 2014; Wolk, Abdelli-Beruh & Slavin, 2012). In addition, the voice training traditions deliberately employ vocal fry to optimize complete laryngeal adduction, and this can serve as a therapeutic task within voice rehabilitation (Van Doren & Rose, 2025; Venkatraman & Sivasankar, 2018; Caffier et al., 2018; Meerschman et al., 2017; Cielo et al., 2011; Gottliebson et al., 2007). Some singing teachers also advocate its use for vocal warm-up and cool-down activities (Nix et al., 2005; Nix, 2016; Emerich, 2003; Bolzan et al., 2008).

So, why would vocal fry not be an acceptable (or perhaps preferred) registration for speech? One answer comes from communication theory. Transmission of information, either through light or sound, relies on a robust carrier signal. In radio transmission, the carrier signal is a high-frequency sinusoid that our ears cannot detect. Its frequency is the dial-in frequency on the radio receiver, AM or FM, generally in the Megahertz range. The message that we hear (music or speech) is the modulation of the carrier, not the carrier itself. Varying specific aspects of a signal, namely frequency, amplitude, and phase allow for information to ride on the carrier signal. In the case of speech, the information is in the form of phonemes and prosodic variations.

For frequency modulation, a general rule in communication theory is that the carrier frequency should be at least ten times the frequency of any modulation. For speech, that translates to the fundamental frequency of the carrier being at least ten times greater than the rate of change of phonemes, pitch, or loudness (the modulated signal). Given that 10–15 Hz is an average phoneme rate for speech, the fundamental frequency should be around 100 Hz or higher to keep a separation between the carrier and the modulation. If vocal fry were to have a fundamental pulse rate of say, 50 Hz, this rate could begin to interfere with the modulation rates of speech (or song). As the speech travels up the auditory pathways, the listener would not perceive the difference between the carrier and the modulation, creating ambiguity in what is heard.

Ambiguity in any signal places a larger cognitive burden on the perceiver. Parsing out the signal from the carrier relies on cognitive processes that would otherwise be free to address other aspects of the signal (Erb et al., 2013). In essence, cognitive load would be increased. The effort to clearly hear intelligible speech may present an undue burden on the listener. This burden is increased when other aspects of the signal such as variation in expected pronunciation (e.g., accents), reduced vocal volume, increased environmental noise, or even the conceptual difficulty of the message accompany excessive amounts of vocal fry. Thus, vocal fry in speech is not so much a vocal health issue as an intelligibility and cognitive burden issue.

Another contribution that vocal fry may have to increased listening effort may be due to the limitations of what is modulated. Because vocal fry sits at the lower end of a speaker’s pitch range, natural variation in pitch throughout speech would be limited. In addition, reduced aerodynamic activity during the production of vocal fry results in limited intensity variation during speech. Lack of sufficient prosodic signals exacerbate the ambiguity in the speech signal by obfuscating meaning and intent.

Personal experience (by one of the authors) from listening to long episodes of vocal fry in speech confirms that intelligibility is reduced and listening effort is increased, areas needing much research. The human voice is an impressive system for transmitting speech, supporting communication and personal expression. When vocal qualities introduce ambiguity or make listening more effortful, they can diminish their effectiveness.

References

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Caffier, P. P., Ibrahim Nasr, A., Ropero Rendon, M. D. M., Wienhausen, S., Forbes, E., Seidner, W., & Nawka, T. (2018). Common vocal effects and partial glottal vibration in professional nonclassical singers. Journal of Voice, 32(3), 340–346.

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