"Voice therapy" or "voice training" refers to any non-surgical technique used to improve or modify the human voice.^[1][2] Because voice is a social cue to a person's sex and gender,^[3] transgender people may frequently undertake voice training or therapy as a part of gender transitioning in order to make their voices sound more typical of their gender, and therefore increase their likelihood of being perceived as that gender. Having voice and speech characteristics align with one's gender identity is often important to transgender individuals, whether their goal be feminization, neutralization or masculinization.^[4] Voice therapy can be seen as an act of gender- and identity-affirming care, in order to reduce gender dysphoria and gender incongruence, improve the self-reported wellbeing and health of transgender people, and alleviate concerns over an individual being recognized as transgender.^[3]

Voice feminization refers to the perception of voice change from masculine to feminine. It is considered an essential part of care for transfeminine people.^[4] Transfeminines trying to feminize their voice represent the largest group seeking speech therapy services, therefore, most studies regarding transgender voice have focused on voice feminization, as opposed to voice masculinization.^[5]

Therapy has been shown to be effective in voice feminization, and the modification of certain voice characteristics, such as fundamental frequency, vocal weight and voice resonance, can help in that effect. Fundamental frequency, closely related to pitch, was initially thought to be the characteristic most effective in voice feminization. Raising the fundamental frequency can help towards voice feminization. However, each person might have different perspectives regarding speech and voice, and therefore the salient characteristics, and their relative impact on femininity, can vary from person to person, and many people are not satisfied with only a change in fundamental frequency.^[6]

What is considered a feminine or a masculine voice varies depending on age, region, and cultural norms.^[5] The changes with the greatest effects towards feminization, based on current evidence, are fundamental frequency, vocal weight and voice resonance. Other characteristics that have been explored include intonation patterns, loudness, speech rate, speech-sound articulation and duration.^[5]

Voice modifications for transgender men typically involve the lowering of the speaking fundamental frequency.^[4] Voice therapy is generally not required for transgender men as the effects of testosterone on the larynx result in a deeper pitch.^[7] However, testosterone replacement therapy does not always deepen the voice to the person's desired level, and others choose to not undergo masculinizing hormone therapy at all.^[4] Voice masculinization therapy can help to further lower the pitch of transgender men and address voice problems associated with hormone therapy.^[4]

In testosterone replacement therapy vocal folds change faster than larynx.^[8] Overdevelopment of vocal folds in an undescended, small larynx can result in a condition named "entrapped vocality" with permanent hoarseness, and lack of passing.^[8] Larynx length can be controlled via exercise, making lowering the larynx a useful tool for transgender men in obtaining a passing voice.^[9] Other areas that transgender men may benefit from training are embouchure and maintaining high CQ (closed quotient, a quotient of how long the vocal folds are touching to how long the cycle of vibration lasts), responsible for "heavy" or "buzzy" voice quality.^[9]

A speech-language pathologist (SLP) may be involved in aiding transmaculine people to achieve their desired voice goals, while usually prioritizing the overall health of the voice.^[10] Therapy techniques may involve finding a person's most comfortable pitch range, using breath support and relaxation exercises, introducing voice strengthening warm-ups, stabilizing posture and increasing chest resonance.^[10]

Another option for transgender men who wish to further lower their speaking pitch is to undergo vocal surgery.^[10]

In the case of AI vocal gender identification examples, key features noted to effect gender perception included fundamental frequency and formant frequency as well as further source related measures including cepstral peak prominence (a rough measure of harmonicity in voice with low values indicating a higher likelihood of dysphonia) and rolloff in energy between the first and second harmonics.^[11][12] A 2020 study in the International Journal of General Medicine noted other factors being involved in gender perception, saying: "a minimum F0 value of 180 Hz required for a voice to be perceived as feminine".^[13]

Vocal gender presentation can be assigned by speakers even as things like fundamental frequency stay the same, especially where we see formant frequencies changing, which is noted as important for gender presentation alongside fundamental frequency.^[14]

While hormone replacement therapy (HRT) and gender reassignment surgery can cause a more feminine outward appearance for transgender women, they typically do nothing to alter the pitch of an adult voice or to make the voice sound more feminine,^[15] unless HRT is started immediately after puberty blockers during teenage years. The existing vocal structure can be surgically altered to raise vocal pitch by shortening the vocal folds, decreasing the whole mass of the folds, or by increasing the tension of the folds.^[5] Transgender women can undergo surgery to raise their vocal pitch as measured by fundamental frequency (F0), to increase their pitch range and to remove access to lower frequency ranges in their voice.^[5] The current pitch-raising vocal surgeries can be split-up into several categories:

• Cricothyroid approximation (CTA) (A common legacy procedure^[5])
  • This surgery tenses and elongates the vocal folds in order to increase vocal pitch. This is done by bringing the cricoid cartilage closer to the thyroid cartilage with sutures or metal plates. The cricoid cartilage is shifted backward and upward and the thyroid cartilage is moved forward and downward. This mimics cricothyroid muscle contraction that tenses and elongates the vocal folds which causes the pitch to increase.^[5][15][16]
  • This surgery effectively locks the patient into falsetto, and sometimes fails over time. The patient is also likely to lose use of their cricothyroid muscle after this surgery. As such, fewer doctors are performing it today.
• Wendler Glottoplasty (Anterior glottal web formation or anterior commissure advancement, also Laser Reduction Glottoplasty/LRG, and VFSRAC, Vocal Fold Shortening with Retrodisplacement of Anterior Commissure)
  • This is the most common surgery today. This surgery shortens the vibrating length of the vocal folds to raise vocal pitch.^[17] The tissue of the anterior part of the vocal folds is removed, and then this tissue is sutured together to form a nonvibrating anterior web.^[5]
  • Laser Reduction Glottoplasty is a variation that involves using a carbon dioxide laser to vaporize the anterior part of the vocal folds. Then the vocal folds are tensed with sutures, causing the pitch to increase.^[18][19] LRG may also include additional laser tuning at the same time (described further below).
  • VFSRAC is another variation invented by Hyung-Tae Kim in Seoul, South Korea, wherein the glottic web is additionally sutured downward in the larynx during surgery to provide further tensioning of the vocal cords and to help preserve the funnel shape of the larynx.^[20]
• Feminization Laryngoplasty (also known as Open Laryngoplasty or Femlar/FL)^[21]
  • This surgery, instead of simply shortening the vibrating length of the vocal cords in the same manner as a glottoplasty, actually removes a portion of both the anterior true and false vocal folds by also removing the front of the voice box. The larynx is then reconstructed with surgical sutures and hardware using the remaining tissue. This has both an effect on vocal size and pitch.
  • This procedure has the ability to provide a better reduction of the adam’s apple beyond that of a tracheal shave and to fix tracheal shave complications that impact pitch.
  • This procedure is also typically combined with a thyrohyoid elevation to raise the larynx in the neck in order to further affect the patient's resonance as well, given doing so reduces the length of the pharynx to more feminine proportions.
  • This procedure is not currently as widely practiced due to being a newer surgery, and its complexity and greater risks in comparison to the other surgeries listed here, with only a few practitioners in the US, Australia, and Thailand currently performing it.
  • The pitch increase and general feminizing effect of this surgery is typically higher than glottoplasty, which may or may not be desirable for patients. The period of pitch instability and recovery is also typically longer as this is a more complex surgery.
  • Some surgeons may refer to their suite of voice feminization procedures as Feminization Laryngoplasty despite not actually performing this particular procedure.
• Laser Tuning (including Laser assisted voice adjustment (LAVA) and Vocal Fold Muscle Reduction (VFMR), and sometimes Laser Reduction Glottoplasty)
  • In these procedures, microlaryngoscopy (a surgical procedure that looks at the vocal folds in great detail) is done in conjunction with a laser, typically a strong carbon dioxide (CO₂) or a weaker KTP (Potassium Titanyl Phosphate) laser that vaporizes portions of the vocal folds. When the vocal fold tissue is in the process of healing and scarring, the vocal folds decrease in mass and increase in stiffness. This results in a rise in vocal pitch.^[22]
  • VFMR vaporizes a larger portion of the vocal folds, including the underlying muscle, while LAVA is more superficial to the surface of the vocal cord and less invasive.^[23]
  • LAVA and VFMR are commonly done to augment the result of the other procedures, as many doctors believe the impact of them alone, without another procedure like Femlar or a Glottoplasty, is minimal on a typical male-to-female transgender patient. VFMR however may occasionally be done in isolation.
  • The term Laser Reduction Glottoplasty (LRG) is also sometimes used to refer to this procedure with or without the additional creation of a glottic web as with a Wendler Glottoplasty, but this varies by context and surgeon.

Additionally, some other procedures are currently being employed in an attempt to provide the patient a more feminine resonance, or timbre, in their voice. These include Thyrohyoid Elevation (commonly performed as part of Feminization Laryngoplasty), which raises the larynx in the neck, and Pharyngeal Narrowing, which removes a strip of tissue from the back of the mouth in order to reduce the size of the pharyngeal resonance cavity.^[24]

Usually, transgender women consider vocal surgery when they feel dissatisfied with voice therapy results, or when they want a more authentic sounding feminine voice. However, vocal surgery alone may not produce a voice that sounds completely feminine, and voice therapy may still be needed.^[25] Although there has been evidence to show that all these surgeries can be effective in increasing vocal pitch as measured by F0, results have been mixed.^[15] However, many patients do report being satisfied with the results.^[15] Negative effects from these surgeries have been noted, including reduced voice quality, reduced vocal loudness, negative effects on swallowing and/or breathing, sore throat, infections and scarring. A positive effect of surgery can be protecting the voice from damage due to the strain of constantly elevating pitch while speaking. Because of the risks, vocal surgery is often considered a last resort after vocal therapy has been pursued.^[5]

As for transgender men, it is generally presumed that hormone therapy does successfully masculinize the voice and lower vocal pitch.^[26] However, this may not be the case for all transgender men. Although it is far less common, surgery to lower vocal pitch does exist and may be considered if traditional hormone therapy did not adequately lower it. Medialization laryngoplasty (or masculinization laryngoplasty) is a procedure where the vocal fold contours are medially augmented with the injection of silastic implants. This mimics the changes that the vocal folds non-transgender men go through during puberty, which causes a lower sounding voice.^[27]

Therapy may take place in an individual or group setting. The most common focus in transgender voice therapy is pitch raising or lowering; however, other gender markers may be more important for an individual to work on.^[5] Clients and clinicians should discuss goals of therapy to ensure that they are working together toward the voice that most fits the person's gender identity.^[4]

In a review of speech literature, Davies and Goldberg (2006) were unable to find any clear protocols for transgender men's voice therapy. Based on the protocols they found for treating transgender women's voices, they proposed the following therapeutic techniques for both voice feminization and masculinization:^[4]

• Imitation of non-transgender people observed in daily life.
• Progressively complex practice while maintaining good voice quality.
• Vocal flexibility exercises to maintain vocal range and voice quality.
• Motor training.
• Identifying and altering voice qualities when coughing, laughing, and clearing the throat.
• Experimentation with a broad range of voice styles.

While there is some evidence for the effectiveness of voice therapy for transgender people, it is still weak. In a 2012 review by Oates (as referenced in Davies, Papp, and Antoni, 2015) of the literature on transgender voice therapy, 83% of studies were found to be at the lowest level of the evidence hierarchy for evidence-based practice, and the remaining 17% were also at low levels.^[5] However, research does show that transgender people who have had voice therapy have high satisfaction with the results, and there is a strong consensus among speech-language pathologists (SLPs) as to what are strong markers of speaker gender in voice.^[5]

The most common concern for transgender women is their pitch and speaking fundamental frequency (SFF) (the average frequency produced in a connected speech sample) because they typically perceive a feminine voice as using a higher pitch. Although pitch is not the most essential element of voice change for these individuals, it is necessary to raise the SFF to a gender-appropriate pitch to help with vocal feminization.^[10] A speech-language pathologist will work with the individual to raise their pitch and provide therapeutic exercises.

The first step in therapy is determining the habitual speaking fundamental frequency of the individual using an acoustic analyzing program. This is accomplished through several tasks including sustained phonation of the vowels [i], [a] and [u], reading a standardized passage and producing a spontaneous speech sample. Then the therapist and the individual determine what the target pitch should be, based on the gender acceptable range for cis women (i.e. a socially acceptable pitch based on the average woman's vocal pitch range). When therapy begins, they establish a starting frequency to work on, that is slightly above the individual's SFF.^[10] The point is to choose a starting pitch that can be produced without strain or excessive vocal effort.^[5] As therapy progresses, the target SFF will gradually increase until the goal has been reached. Progression moves from using the target pitch in a sustained vowel to using it in a 2-5 minute conversation.^[10]

Semi-occluded vocal tract (SOVT) techniques may be used to facilitate voice production in the higher pitch range. SOVT techniques include phonating into straws, lip or tongue trilling, and producing multiple speech sounds such as nasals (e.g., [m] and [n]), voiced fricatives (e.g., [z] and [v]), and high vowels (e.g., [u] and [i]). There are two exercises that are often used: producing a pitch glide that goes from the middle of the pitch range to the upper pitch range; and a messa di voce exercise, where the voice goes from soft to loud to soft again. SOVT techniques have the individual prolong their voice at a higher pitch, which may help make voice production at a higher, non-habitual pitch easier and more efficient.^[5]

Pitch can also be altered through voice resonance modification. The length of the vocal tract affects the resonance of the vocal tract, which in turn affects the pitch. Cis men tend to have vocal tracts that are 10-20% larger than those of cis women, and therefore cis men have a lower vocal tract resonance, and a lower pitch, than cis women. Modifying the length of a vocal tract results in a change in resonance and in pitch, as can be shown by pronouncing a prolonged [s] while protruding and retracting the lips. Transgender women can use techniques, such as retracting the lips, to shorten the vocal tract and sound more feminine.^[28]

A lack of training on how to use their new voice may cause some transgender men to have increased muscle tension.^[10] Therefore, a speech-language pathologist can give individuals vocal exercises to help find their optimal speaking pitch and maintain overall vocal health.^[10] Adler, Hirsch, & Mordaunt (2012), describe the following therapy techniques for transgender men:

• Optimal pitch: Rather than straining to achieve a lower speaking pitch, a comfortable pitch range should be sought. This range is generally approximately between 100 and 105 Hz.^[10]
• Diaphragmatic breathing patterns: In order to maintain their new speaking pitch, transgender men need to establish an appropriate breathing pattern to support their speech output. Establishing a stable speaking posture is also important to optimize pitch and breath support.^[10]
• Warm-up exercises: A person can do these at home to help to strengthen the voice, maintain optimal pitch and prevent vocal fatigue. Resting the voice after long periods of use is also important.^[10]
• Relaxation Techniques: The speech-language pathologist may teach tension-releasing techniques for the jaw, tongue, shoulders, neck and overall laryngeal area.^[10]
• Chest resonance: Head resonance is more commonly used by women, and therefore transgender men must establish a pattern of chest resonance to match their lower speaking pitch. Exercises can help establish this chest resonance and help a person lower their larynx.^[10]

Non-verbal communication may have more of an effect on a transgender person's readability than verbal factors such as pitch or resonance.^[10] Regardless of what is most effective, congruency between a person's visual and auditory gender presentation contributes greatly to their perceived authenticity.^[10] Non-verbal communication includes posture, gesture, movement, and facial expressions.^[4] In a discussion of the differences between masculine and feminine non-verbal behaviour, Hirsch and Boonin (2012) describe feminine communication as generally more fluid and continuous. Examples of feminine non-verbal communication behaviours include more smiling, expressive and open facial expression, more side-to-side head movement, and more expressive finger movements than men.^[10] Deborah Tannen's book, You Just Don't Understand (1990), is referred to by the authors as a seminal work on the difference in men and women's non-verbal communication.^[10]

Within the speech therapy context, non-verbal communication may be targeted through the encouragement of focused observation, offering feedback on the client's self-defined non-verbal goals, offering information about the differences between men and women's non-verbal communication, and/or referring to peer support or expert services.^[4]

While some specific psychosocial issues faced by transgender people are often addressed through psychotherapy, there are psychosocial factors that can influence transgender voice therapy. For example, some clients feel that hormone therapy for transitioning changes concentration and emotional stability, which could affect receptiveness to speech therapy.^[4] Davies and Goldberg (2006) also note that an altered voice may feel inauthentic, and it may take time for the client to feel as if their new voice is an expression of their true self.^[4]

Transgender erasure describes systematic, individual, or organizational discrimination against transgender people.^[29] Informational erasure and institutional erasure were identified in a 2009 Canadian study of health care for transgender people as being the most prominent barriers to care.^[29] Informational erasure involves a lack of knowledge, or a perceived lack of knowledge, about transgender health care. This may manifest itself in health care providers being more reluctant to treat transgender clients because of an unwillingness to find information about their specific population.^[29] Institutional erasure describes policies that do not accommodate transgender identities or bodies. For example, forms, texts, or prescriptions may refer to a person by an inappropriate name or pronoun.^[29] Issues of erasure may hinder a transgender person's ability to find speech therapy services, or may affect the person's comfort with speech therapy.

In addition to paying attention to problems of erasure, Adler and Christianson (2012) suggest that a clinician should be sensitive to the following areas when working with a transgender client:^[10]

• Gender attribution and discrimination
• Possible feelings of shame and guilt
• Consequences of the coming out process
• Spouse, partner, or family attitudes
• Employment issues
• Incidence of HIV/AIDS
• Racial and cultural differences

The authors note that this is not an exhaustive list of possible psychosocial factors and that every client is different. Psychosocial factors such as these may affect a transgender client's progress and prognosis in speech therapy.

Few studies have considered the potential repercussions of age on therapy. Currently, there is no consensus regarding speech therapy for adolescents.^[30] During adolescence, there is an increase of both vocal tract size and vocal fold length, especially for those assigned male at birth, which affects the voice and pitch. Because of these physical changes and hormonal changes, it is difficult to focus on pitch.^[31] Previous studies have shown that therapy shaped from adult therapy can be effective.^[31]

Few studies have looked into the transition in the elderly. A survey has shown that many elderly members of the LGBT community do not disclose their LGBT status to their clinicians, including members that receive speech therapy; they choose not to disclose this information because they are afraid it would negatively affect their access to services.^[32]

There are two major areas of controversy for professionals working on the voices of transgender people. The first is regarding vocal surgery, and the second is regarding genderfluid and bigender voice therapy.

Professional opinion is mixed regarding the use of vocal surgery.^[5] There is currently a lack of outcome data, particularly longitudinal data, for pitch-elevating surgery, and outcomes have not been well-monitored over time.^[4] Because of this, some SLPs do not think that phonosurgery is a viable treatment option.^[4][5] Others believe it is, and still others believe it should be considered only as a "last resort" after the desired pitch change has not been seen in therapy.^[4] Critics cite variability in outcome, lack of outcome data, and reported negative effects like compromised voice quality, decreased vocal loudness, adverse impact on swallowing/breathing, sore throat, wound infection, and scarring as reasons to avoid vocal surgery.^[5] Proponents argue that surgery may protect a person's voice from damage caused by repetitive strain to elevate pitch in therapy.^[5] Ultimately, the decision to undergo surgery is up to the patient, with input from a knowledgeable physician and SLP.

There is also some controversy regarding the use of a genderfluid voice. A person may want to have both a masculine and a feminine voice in their vocal repertoire, possibly to fit with their own genderfluid identity, or to read as a different gender in different contexts.^[5] Some clinicians will not train genderfluid voice, arguing that it decreases the opportunity for practice, and it may be difficult or even damaging to the vocal folds for the person to switch from one voice to another. However, Davies, Papp and Antoni (2015) reference the ability of actors to use different accents and dialects, and people to learn different languages as a sign that training a genderfluid voice may be a viable treatment goal.^[5]

• Chest voice
• Falsetto
• Speech pathology
• Vocal fry
• Transgender health care
• Language and gender
• List of transgender-related topics

• World Professional Association for Transgender Health
• University of California, San Francisco Center of Excellence for Transgender Health