Adapted from original articles on Wikipedia
Speech therapy is the corrective or rehabilitative treatment of physical and/or cognitive deficits/disorders resulting in difficulty with verbal communication. This includes both speech (articulation, intonation, rate, intensity) and language (phonology, morphology, syntax, semantics, pragmatics, both receptive and expressive language, including reading and writing). Depending on the nature and severity of the disorder, common treatments may range from physical strengthening exercises, instructive or repetitive practice and drilling, to the use of audio-visual aids.
Voice therapy or voice training refers to any non-surgical technique used to improve or modify the human voice. Because voice is a gender cue, transsexual women frequently undertake voice therapy as a part of gender transition in order to make their voices sound female, and therefore increase their readability as females in society. Transgender people and crossdressers who present as women may also desire to feminize their voices and therefore undertake voice therapy.
Voice feminization is the desired goal of changing a perceived male sounding voice to a perceived female sounding voice. The term voice feminization is used to describe what the desired outcome of surgical techniques, speech therapy, self-help programs and a general litany of other techniques to acquire a female-sounding voice. The methods used for voice feminization vary from professional techniques used for vocal training, speech therapy by trained speech pathologists and several Pitch altering surgeries.
Vocal sound is produced by air traveling upwards from the lungs through the opening of the larynx called the glottis where the vocal folds vibrate and phonation or voicing occurs. The vibrating vocal folds produce a sound that is modified by chambers (like rooms) of the throat and mouth creating resonance frequencies. The size of the chambers directly affects these frequencies. As the size of the chambers increase the deeper (or lower) the formant frequencies become. These chambers play a very important role in the perception of the timbre (rich, nasal, flat) of the voice. The articulators (tongue, lips, jaw, and soft palate etc.) shape the sound into recognizable speech. Then it is the prosodic features (speaking rate, inflection, pauses) which makes unique speech patterns.
There are several frequencies or harmonics produced at the lips. The fundamental frequency (F0) or the number of times per second that the vocal folds vibrate (in hertz), the conversational fundamental frequency is approximately 200 Hz for adult women and 125 Hz for adult men. Many of the voice feminization techniques, including those of surgeons, focus on the fundamental frequency but do little to address how the sound is modified by the articulators or prosodic features. Speech therapists and professional voice coaches offer training in both changing the fundamental frequency and how to change the perception of voice quality.
Voice masculinization is the opposite of voice feminization, being the change of a voice from feminine to masculine. Voice masculinization is not generally required for transsexual men as the masculinising effects of testosterone on the larynx are usually sufficient to produce a masculine voice.<ref name="androvoice">Template:Cite journal</ref> However, Alexandros N.Constansis has stated that "Apart from being unfair to transmen, is also overtly simplistic" and cites Davies and Goldberg in saying that "testosterone doesn’t always drop pitch low enough for FTMs to be perceived as male". <ref name="">Template:Cite journal</ref>
Differences between male and female voices
Pitch.: Females usually have higher-pitched voices than males. Many people believe that this is the only essential difference between male and female voices; however, that is not the case. The fundamental frequency (F0) of male voices typically ranges from 100 to 150 Hz while ranging from 170 to 220 Hz in females.<ref>Template:Cite web Template:Dead link</ref> In a 1988 study in which listeners identified the sex of a speaker by voice alone, all individuals identified as male had an average F0 of 160 Hz or less; all identified as female had an average F0 above 160 Hz.<ref name="speechlit">Template:Cite web Template:Dead link</ref>
Resonance, also known as timbre, is another important voice characteristic. According to Melanie Anne Phillips, resonance is more significant in "gendering" one's voice than pitch. One TS woman who raised her average F0 from 110 Hz to 205 Hz over four months was still frequently identified as male on the telephone, which may have been due to the resonance of her voice.<ref name="speechlit" /> However, Anne Lawrence believes that pitch is a more significant gender cue than resonance. An additional factor is the different size of the average vocal tract of males and females. What Melanie Anne Phillips calls "resonance", in terms of phonetics is distribution of formant frequencies which depends on vocal tract length (VTL) – from vocal folds to lips. Men have larger skulls, also male larynx is positioned lower in relaxed state, so men have longer VTL. Shortening VTL makes voice to be perceived more feminine. It's possible to shorten VTL by will: by shifting larynx upwards and backwards by means of straining the pair of stylopharyngeus muscles. Straining the pair of stylohyoid muscles and posterior bellies of the pair of digastric muscles also helps. These three pairs of muscles are strained during swallowing and gargling, it's why Melanie Anne Phillips talks about gargling technique. Place your fingers on your throat lightly, feel where the Adam's Apple is. Swallow, feel how it goes far up, then down. Learning how to shift it upwards and backwards while talking is the key to successful voice feminization [as discussed on the voicets yahooGroup].
- Intonation: men tend to speak in a more monotonous tone, while women tend to use a wider range of tones when speaking.
- Pronunciation: Some theories believe that men and women tend to pronounce words differently. 
- Discourse patterns: According to Melanie Anne Phillips, men tend to use words, sentence structures, and pragmatic features in which they are assertive, while women are more submissive.
Like other gendered characteristics, considerable overlap exists between male and female vocal characteristics, especially the psychological ones.
Transsexual women who go through puberty as males will usually develop voices characteristic of males. Hormone therapy does not alter a trans woman's voice once it has masculinized<ref>Template:Cite web</ref>; therefore, trans women who intend to pass as females need to have help with vocal training to feminize their voices.
Vocal training is done formally with the help of several types of professionals and privately by the use of self-help resources including audio or video tapes programs, books, information garnered from websites or chat groups that shares this particular interest. Some trans women have feminized their voices with no assistance.
The advantage of going through a speech pathologist instead of many of the other professionals that offer training or trying to learn on your own with self-help programs is that vocal cords can easily become irritated and even develop callous-like growths called vocal fold nodules as the result of incorrect use of the voice and from modifying one’s voice too quickly. Individuals who participate in a voice feminization program are trained to self-monitor and become more aware of their vocal quality. They learn to recognize where and how they produce sound, how they are resonating that sound, and how they physically carry themselves and their voice. Related aspects of communication are also addressed including: breathing patterns, gender related non-verbal communication and vocal hygiene.
Some trans women find voice training to be difficult, while others consider it unnecessary. While most trans women would prefer to have completely feminine voices, many are unable to achieve this goal. Some post-transition trans women have masculine voices, and many have peculiar female voices that may draw attention.
Voice scientists, speech pathologists, language pathologists and ENT physicians (otolaryngology) organize voice production into five components. They are:
- Respiration (or breath) - power source
- Phonation - sound source
- Resonance - sound modifier
- Articulation - speech modifier
- Prosody - melodic aspects of speech
In training for a feminine voice, all five components are usually included.
Things that help make a voice feminine
- Pitch Feminine voices are higher; this may be the most important concern.
- Pitch Range Men tend to be more monotone, varying the pitch helps feminize the voice.
- Speech Rate - Men typically speak at a steady rate, while women tend to speak in shorter bursts followed by pauses.
- Language patterns - The language that women use differs from that of men, although the degree of variation can be quite different from one language to the next (relative to English, it is extremely pronounced in Japanese, for instance).
- Tag Questions - Example: "It's a beautiful day, isn't it?" A man, on the other hand, would be more likely to simply declare, "It is a beautiful day." 
- Supportive environment - As with any skill, speaking with a feminine voice may be easier without the stress of extreme consequences for failure (for example, being identified as a transsexual by someone to whom one is not out.) Additionally, opportunities to use the feminine voice in conversational situations (as opposed to speech-therapeutic ones) may be helpful in polishing the skill.
NB: These suggestions are based on literature from language and gender scholarship such as Lakoff (1975) and the work of Deborah Tannen. However, this work has been critiqued heavily for representing only stereotypes of how women speak, rather than how women actually speak, and additionally for representing middle-class white heterosexual women to the exclusion of all others. 
While hormone replacement therapy and gender reassignment surgery can cause a more feminine outward appearance, they do little to alter the pitch or sound of the voice. The existing vocal structure can be surgically altered using procedures that include
- Cricothyroid approximation (CTA) (is the most common)
- Thyrohyoid approximation
- Laryngeal reduction surgery (surgical shortening of the vocal cords)
- Laser assisted voice adjustment (LAVA)
There was, until recently, limited evidence as to the efficacy of these surgeries in raising the fundamental frequency over the course of several years. However, since the late 1990's, surgeons performing CTA and other 'voice' procedures at Charing Cross hospital, (Hammersmith, London), have conducted long-term follow-up studies indicating "high" levels of patient satisfaction with both surgical and social health outcomes. All of these modes of 'voice surgery' may or may not have an effect on resonance or other vocal characteristics. ClaudineJ is one trans woman who reports long-term, (12 years+ at 2010), beneficial changes in both pitch, resonance and speech quality from CTA surgery. Many in the transsexual community have previously been led to regard voice surgery as 'inadvisable', while others regard a socially acceptable standard of feminine speech to be indispensable (and further surgery an acceptable risk). Anecdotal evidence has suggested that (CTA) voice surgery can be expected to raise pitch above female norms in the immediate post-operative period (when sutures are used to create the adjusted 'approximation'); however the (more modern) use of titanium clips avoids this problem, maintaining a correct and even tension on the vocal folds, in the immediate and longer term. Of course, laryngeal surgery carries risks and some patients experience 'raspiness', or, much more rarely, complete loss of voice. Deirdre McCloskey is one trans woman who experienced complications from voice surgery.