ELECTRONIC ARTIFICIAL LARYNGES - HOW DO THEY DO THAT??
Artificial larynges (ALs)* produce sound which substitutes for the vocal tone that the user is no longer able to produce because the larynx has been by-passed, has been removed or is non-functional. Once the AL's sound is introduced into the oral cavity, the user can shape it into words with tongue, jaws, lips and teeth just as he/she would have done with sound from the larynx.
An electronic AL uses a battery powered electronic circuit to generate a vibrating tone - rather like a refined door buzzer. The tone is designed to have a frequency (pitch) range close to that of the average human speaking voice and is adjustable to suit individual preference. Some ALs offer quick change in tone to provide vocal inflection. Electronic ALs currently come in two types:
Extra-oral (or "neck-held") ALs have a vibrating head that is pushed against the tissues of the neck to transfer sound energy into the throat, from which it enters the oral cavity. When neck placement is not possible due to poor condition of the tissues or due to head/neck position or supports or equipment that interfere with placement, some users can get reasonable results by pressing the instrument against the cheek. However, many people will not find either neck or cheek placement useful and will require an intra-oral AL.
Intra-oral ALs introduce sound directly into the mouth, either through a small tube which is connected to an AL held in the hand or via an upper palate plate containing all the components except the switch.** Many neck-held units have oral adapters that fit over the head of the instrument and hold tubes and thus allow a choice of extra- or intra-oral use. A tube or palate piece often offers some interference with articulation, but users will benefit from guided practice. People with excessive saliva production may have difficulty with intra-oral devices due to clogging of tubes or openings.
Regardless of which type of AL is chosen, the user must be able to turn the sound on/off, since a continual buzz, when no words are being spoken, would be annoying to listeners and would use up the battery too quickly - and, also, the unit must be held up to the mouth/neck. To accommodate those with limited or no use of hands or arms, there are various adaptations of the Cooper-Rand intra-oral device. ALs (except the palate type) also may be held and operated by another person. Placement and on/off coordination are awkward and the user cannot speak instantly when he/she wishes, but in temporary or difficult situations, many people find this preferable to no speech at all.
Patients will depend upon a speech therapist to help them choose an instrument and to give them assistance/instruction in placement, articulation, and general use and care, including changing batteries.
* Artificial larynges are also often called ALDs (artificial larynx devices) or Speech Aids.
** The palate device has limited voice volume due to size restrictions - and the individual fitting and dental work required make this unit impractical for temporary use in a clinical setting and also make it relatively expensive. However, it does not require lifting the hand to the head/neck since the remote button can be operated at the hip level and it may be worth considering for long term use in quiet areas or with a voice amplifier.
Also available: pneumatic ALs which duct exhaled lung air through the stoma, into a tube and through a reed, which vibrates, creating sound which continues through the tube and into the mouth for the user to shape into words. They are less expensive than Electronic ALs and sound more like a regular human voice. However, they often require the use of both hands to hold the fitting over the stoma and the tube positioned properly in the mouth. The tube must be of a fairly large diameter to provide sufficient sound volume, so articulation needs more practice.
Note: Artificial larynges should not be confused with "talking trachs" and "speaking valves" which are designed to make use of the vocal cords, or with tracheoesophageal puncture (TEP) prostheses which duct lung air from the trachea to the esophagus allowing laryngectomees with suitable tissue structure to produce esophageal speech using lung air.