Voice and communication are crucial aspects of daily life for all humans. Within the transgender community voice and communication are often brought to the forefront when the incongruence between gender identity and voice/communication style are greatest. Aspects of voice and communication are highly related to gender  and culture. These include pitch, intonation, loudness and stress patterns, voice quality, resonance, articulation, speech rate, language, and nonverbal communication.[3,4] Altering the aspects of voice and communication related to gender have been reported to reduce gender dysphoria while improving mental health and quality of life.
There are many resources to help trans people identify communication characteristics that may be targeted to develop more gender specific communication style. These may include vocal coaches, theater professionals, singing teachers, and movement experts. Specialty trained speech language pathologists (SLPs) are best equipped to facilitate overall vocal health and efficiency, in addition to behavioral changes related to voice and communication for transgender people.[1-3,5] Otolaryngologists with subspecialty training in laryngology are skilled in vocal fold surgery techniques (phonosurgery) which may act as an adjunct to voice therapy.
Approach to voice complaints
Transgender people may present with voice complaints related to quality change or fatigue that are unrelated to gender transition. This could be non-organic, organic, iatrogenic, or idiopathic in nature (Table 1). It is important that a comprehensive voice evaluation is completed, including voice and communication needs related to gender transition, by a laryngologist and voice trained speech pathologist prior to initiating voice treatment. Evaluation should include a thorough laryngeal examination including videostroboscopy to assess the anatomy and physiology of structures related to voice production.
The overarching treatment goal for transgender people who present with voice and communication complaints is to aid in achieving a gender congruent voice in an efficient and safe manner. Treatment should be patient specific and can be accomplished through behavioral and medical/surgical intervention.
In a study of self-perceptions of trans females, it was found that the strongest contributor to communication satisfaction was voice. The components of voice production include pitch, resonance, intonation and intensity.
Pitch may be perceived as the most important factor for voice and subsequently gender identification.[2,7,8] A strong marker for the perception of female voice is an average speaking pitch of 180 Hz in a range of approximately 140 to 300 Hz.[9,10] The average non-transgender female pitch is approximately 225Hz while the average non-transgender male pitch is approximately 125Hz. A pitch range that is considered gender neutral generally falls between 155-185Hz. It has been demonstrated that increasing speaking pitch impacts the degree of voice feminization.[9,12,13] However, increasing pitch into the female range does not necessarily result in listener perception of the speaker as female.[7,14] Research indicates that other voice characteristics such as speaking pitch range, intonation, resonance, and voice quality play varying roles in the perception of femininity. Similarly, pitch floor (the bottom of the pitch range) and the proximity of the usual speaking pitch to this floor is thought to influence the perceived maleness of voice, rather than the speaking pitch alone.
There is some discrepancy in the literature on the role of resonance, as studied through formant (harmonic) frequencies. Harmonic frequencies are multiples of the root speaking pitch; the combination and configuration of formant frequencies for any given sound determine its "tone." Contributors to vocal resonance include the length of the pharynx and size of the sinuses, which in transgender women who have undergone a male puberty are fixed in a larger size than with non-transgender women. One report suggests a primary role of resonance in perceptual identification of the speaker's gender. However, another study reports that a combination of both pitch and resonance are found to contribute to perceived femininity and should be addressed.[4,15]
Intonation, or variability in pitch during speaking, is a recommended component of behavioral intervention for voice feminization. In one study, there were no significant differences in overall intonation patterns observed between genders. Transgender participants who were identified as female had a larger number of upward intonation patterns and larger semi-tone range within utterances than other groups. Transgender women who were misidentified as male had fewer upward and more downward intonation patterns than females and transgender females who were correctly identified.
Intensity and other voice characteristics contributing to perception of gender
Increasing breathiness [9,17] using lower vocal intensity [13,17] and avoiding vocal fry  can contribute to voice feminization.
The components of voice production are primarily addressed through behavioral voice therapy. It is thought that the total number of voice therapy sessions, in addition to living full time as female might be predictive of response to behavioral intervention.
Two common voice therapy techniques include flow phonation and resonant voice therapy. Flow phonation targets balanced exhalation of airflow during voice production to achieve vocal efficiency and may aid in altering breathiness and intensity. Resonant voice therapy focuses on achieving easy phonation while experiencing the energy or vibration of sound in the oral cavity therefore altering resonance. When used with transgender women, oral resonance therapy is reported to increase femininity by altering resonance to more closely approximate female resonance with a spontaneous increase in pitch. Vocal function exercises, a systematic program of physiologic voice exercises that are designed to strengthen and balance the laryngeal musculature and to achieve balance between airflow and muscular effort, do not seem to improve therapy outcomes in trans women.
Long-term gains have been reported related to listeners' perception of gender following voice therapy that targeted primarily pitch and resonance. Voice therapy has also been shown to generate changes that significantly impact listener's perception of femininity; however femininity is perceived as higher immediately following therapy than 15 months later. Trans women having varying voice goals and may choose to use feminine communication patterns all of the time or situationally.[1,17] The decreased perception of femininity over time, mentioned above, and the variable application of feminine voice may indicate the place for a maintenance program following voice therapy. While research is required in this area, intermittent ?checking-in' and recalibration of voice components may be warranted.
Studies indicate that trans women attain improvement in voice following voice therapy and most are satisfied with the outcome.[17,21] If, after a course of behavioral therapy the desired outcome is not achieved, surgical intervention may be considered. At this time, surgical intervention primarily targets alteration in pitch. Pitch change alone has been shown to be insufficient for listeners to accurately identify gender [7,14] and should not be considered the initial or only treatment for voice feminization.
Effects of hormone therapy on voice
Hormone therapy in trans women, while resulting in reduction of testosterone levels and increases in levels of progesterone and estrogen, has not been perceived to have a significant effect on voice or the perception of feminine voice. Vocal pitch is a function of the overall size and mass of the vocal folds, and there are few if any formal studies in the English literature that support that hormonal manipulation in post pubescent males will significantly alter vocal pitch. During male puberty, exposure to testosterone results in hypertrophy of the laryngeal muscles, cartilage and mucosa. This results in the characteristic voice changes that occur in pubescent males.
While withdrawing testosterone result in a modest degree of mucosal and muscle thinning, this effect takes years and cannot reverse the significant hypertrophy caused by the previous exposure. Thus pitch, which is related to vocal fold mass and size remains lowered, and the overall effect on voice from withdrawal of androgens is minimal once these changes have occurred. This is consistent with what is seen in females who have been exposed to androgens for the treatment of medical conditions. Once the exposure has occurred and the vocal pitch is lowered, the withdrawal of androgens is not generally associated with a significant re-elevation of pitch. Therefore, if behavioral interventions do not result in a sustained improvement in patient satisfaction with the characteristics of voice, then surgery may be considered.
As previously stated, pitch of voice is related to overall vocal fold mass and the tension of the vocal fold while the patient is producing voice. We can all voluntarily increase the tension in our vocal folds to elevate pitch. This, however, requires continuous muscular effort. With attention, training and time, this increased effort may become habitual. However, even successful patients often complain of a sensation of vocal effort and/or fatigue at the end of the day. Therefore, surgeries have been designed to elevate pitch by either altering vocal fold tension, mass, or both. The tendency of biological structures to relax when artificially stretched or tensed represents a significant challenge to surgical approaches to voice modification. Furthermore, procedures which attempt to alter the tension by scarring the vibratory portion of the vocal fold, or reducing the overall vocal fold mass, risk inducing negative alteration in the delicate tissue of the vocal folds, which must vibrate at high frequencies to produce normal vocal quality.
Surgical attempts to elongate the vocal folds
One of the earliest procedures reported for elevation of vocal pitch is a cricothyroid approximation, or type 4 thyroplasty, initially developed in the 1970s. In this surgery, the vocal folds are placed under permanent increased tension, using sutures that approximate the front aspect of the thyroid cartilage to the cricoid ring. A year-long longitudinal report of 11 patients (only 1 of whom was transgender) who underwent this procedure showed initial promise immediately postop. However, while pitch did remain elevated at one year, it was lower in comparison to the postop pitch, and it was theorized that the vocal chronic vocal tension resulted in stretching of the tissue with relaxation or that the sutures pulled through the cartilage. This has led to proposed modifications to the originally described procedure, either by altering the method of suture placement, or by scarifying the thyroid to the cricoid. Other case series have found similar results of initial improvement with benefits that wane over time.
Other attempts to permanently elongate the vocal folds to increase tension have resulted in similar outcomes.[27,28] These modifications have proposed pulling the anterior aspect of the vocal folds forward without fixing the cricoid to the thyroid. The theorized advantage is that the patient would be able to further modulate pitch. However, this has not been the outcome and the results are variable when the patients are followed long-term.
Surgeries to reduce vocal fold mass and length
In 1982, Donald et al  proposed surgery to reduce the size of the vocal folds, and create a web between the anterior portion of the vocal folds, by opening the larynx, removing the front third of the vocal folds and suturing the larynx closed. This surgery has the advantage of being able to be combined with procedures to reduce the prominence of the larynx in the neck. Though the length of follow-up is not noted, Donald reported on successful pitch elevation and patient satisfaction in 3 patients. The procedure has been modified by other surgeons, and combined with shortening of the pharynx by bringing the larynx and the hyoid bone closure together. In a series of 94 patients (74 of whom were followed for approximately 1 year or more), these authors reported an average elevation of pitch from 139 Hz preoperatively to 196 Hz postoperatively. Complications were relatively rare and transient. While promising, the results were somewhat unpredictable in terms of overall vocal quality and vocal range. In addition, while the surgery is generally well tolerated, it does place the airway at risk and require an external incision in the anterior neck skin.
Surgeries to increase tension by producing scar on the vocal folds
As previously mentioned, vocal fold vibration rate, which determines the pitch of the voice, is affected by vocal fold mass (as the mass decreases, the vibration rate or pitch increases) and tension (as the tension increases the vibration and pitch increases). This has led surgeons to attempt to elevate pitch by increasing tension through scarring the surface of the vocal folds or scarring the front portion of the vocal folds together to shorten the portion available for vibration. The main advantage of these types of procedures is that they can be done through the mouth without an incision in the neck, are well tolerated, and do no place the patient's breathing at significant risk. The main disadvantage is that healing and scar production can be unpredictable and results variable.
The initial reports of this type of surgery were present by Wendler in 1989. The procedure, which has come to be known as the Wendler glottoplasty, is relatively easy to perform. The mucosa or skin from the front aspect of the vocal folds is removed. This can be done with either a CO2 laser, or with traditional non-powered instruments; the front aspect of the vocal folds is then sutured together. Variations on this procedure have replicated results in multiple small patient series from other centers.[12,22,33,34] In general, the vocal fold pitch is significantly elevated, but the overall pitch range and vocal loudness levels are reduced. In all patients, there is a modest increase in degree of vocal roughness postoperatively, and this is more noticeable when the procedure is performed in patients over 50 years of age. The procedure can also be repeated if healing does not result in as much scar as desired, and can be performed in patients who have failed other types of surgery.
Finally, some surgeons have attempted to create scar on the top/superior surface of the vocal folds, either as a separate procedure  or as an adjunct to Wendler glottoplasty. These attempts have not been shown to produce reliable results or benefits over glottoplasty alone, and are likely best avoided.
Far fewer transgender males present for voice evaluation and treatment than transgender females. This may be related to the reduction in pitch that transgender males experience as a result of hormone therapy.[38,39] As a result, the need for voice therapy for transgender men may be underestimated. The hormone induced pitch change is not always without problems and it remains unclear if it is in all cases sufficient for the speaker to be identified as male.[38,39] Research supports that voice and communication should be targeted in voice therapy.[2,5,40-42]
With hormone therapy, final lowered pitch is achieved sometime after 1 year. Following response to this treatment, it is reported that about 75% of trans men are identified as male by telephone. This leaves 1 in 4 transgender men who may not be perceived vocally as male. The perceived masculinity of voice is related not only to pitch but also to the proximity of the habitual speaking pitch to the pitch floor, or lowest pitch. Following behavioral intervention with a speech pathologist, it was demonstrated that speaking pitch decreased by an additional 35Hz and pitch instability and voice fatigue resolved.
Increased 'chest resonance' is suggested as a goal in voice therapy. Achieving balanced resonance during voice production contributes to overall vocal efficiency and may play a role in the reported improvement in voice complaints for trans men following voice therapy. These changes in resonance are further supported by data showing a change in formant frequencies (the acoustic correlate of resonance) during the first year of hormone treatment in conjunction with behavioral intervention.
In one study, there were no significant differences in overall intonation patterns observed between 4 gender groups (12 non-transgender males, 12 non-transgender females, 6 transgender men, 14 transgender women). However, transgender women who were misidentified as male had fewer upward and more downward intonation patterns than females and transgender females who were correctly identified. Decreasing pitch variation, while avoiding monotonicity is suggested for trans men.
Vocal intensity in trans males is not well documented in the research literature. However, if increasing breathiness [9,17] and using lower vocal intensity [13,17] contributes to voice feminization, it may be considered that reducing breathiness and avoiding a soft voice may be perceived as more masculine.
While pitch is primarily addressed through hormone therapy and secondarily by voice therapy, the other components of voice production are primarily addressed through behavioral voice therapy.
Flow phonation and resonant voice therapy are two common voice therapy techniques. Flow phonation targets the balanced exhalation of airflow during voice production using respiration as the power source to achieve vocal efficiency. Resonant voice therapy focuses on achieving easy phonation while experiencing the energy or vibration of sound in the oral cavity. The combination of these techniques can work to maximize voice production targeting pitch, resonance, intonation and intensity for trans men; efficacy data is needed to support this.
Some transmasculine spectrum people seek only some voice masculinization, and desire flexibility with their voice and communication. While the literature supports the role of voice therapy for voice masculinization,[40,41] this is an area that needs further attention. With this in mind, voice therapy should be patient specific and physiologically based to achieve patient and therapy goals in a vocally efficient and safe manner.
Effects of testosterone hormone therapy on voice
90% of trans men will achieve acceptable voice results, lowering of pitch into a gender neutral or male range, after 4 to 5 months of taking exogenous androgens. In multiple reports of small series, the average speaking pitch dropped for a female range of 190- 200 Hz to an acceptable male range of 100 to 140Hz.[5,43] However, while lowered pitch occurs as a consequence of thickening of the tissues due to the effects of androgens, in some cases male speaking patterns must be learned through behavioral therapy. 10% of patients or more will have some difficulty during transition either due to inability to produce efficient vocalizations with the altered laryngeal apparatus, or an inability to naturally adopt male speaking patterns. These patients usually respond to counseling with a certified speech-language pathologist who has experience in managing individuals with transgender voice issues.
As hormonal therapies and behavioral therapies are effective in helping 90% of transgender men achieve acceptable voice, surgical intervention is rarely indicated in this group. If needed, however, relaxation thyroplasty, designed to reduce the tension of the vocal folds can be performed. This same surgery is used in male patients with inappropriately elevated pitch and results in a reduction of pitch if performed in the original method  and an even greater reduction if modified as described by other authors. Typical pitch reduction is in the range of 100 Hz and usually results in the patient attaining an acceptable male vocal pitch. However, as the vocal cord tension is less controllable after the intervention, the voice is often perceived as more rough and with less volume.
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