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Is there any situation anatomically, where a human could understand the speech of others perfectly, without any capabilities of speech themselves, but would retain the ability to whistle with a tune?

I was led to believe that the larynx is the most important thing for creating the sounds in speech, however I don't know if a damaged larynx would necessarily not allow someone to speak.

I would suggest someone who has no tongue cannot speak coherently, however I would imagine that the tongue is instrumental (pardon the pun) in creating a range of sounds whilst whistling.

Is there perhaps a part of the brain that could be affected in order to stop someone speaking? Or would this also mean the person could not understand speech either?

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  • $\begingroup$ Thanks for splitting your questions - it is appreciated. $\endgroup$ – AliceD Mar 23 '15 at 10:35
  • $\begingroup$ You can make a whistling sound by pushing air through your teeth. $\endgroup$ – skymningen Mar 23 '15 at 10:57
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Short answer(s)
Someone with a damaged larynx may still speak with the use of a speech aid (electronic larynx).

The ability to understand speech does not necessarily mean one can speak normally. There are neurological disorders where folks can understand speech, but have difficulty producing it.

Background
A full removal of the larynx (laryngectomy) prevents the patient to produce speech because the vocal chords are removed. However, with the use of a voice prosthesis this can be solved (Cancer Research UK).

There are neurological disorders where one can still understand speech, but has impaired ability to generate it, called apraxia. Apraxia can be acquired or congenital (developmental) (NIH). The developmental type is not well understood a the neural level (Dyspraxia Foundation UK). The acquired type is known to occur through damage to specific brain areas, for example due to trauma or stroke. One of these areas associated with acquired apraxia is Broca's area (Graff-Radford et al., 2014), which is a brain area intimately associated with the production of speech .

Broca's area
Broca's area. Source: UC Irvine

However, although damage to this area can result in pure apraxia (i.e., impaired speech but normal speech understanding), it can also result in Broca's aphasia, which means that language understanding is also impaired (American Heart Association). Moreover, regarding your specific question, apraxia is characterized by impaired speech, but not a total lack of speech production.

Reference
Graff-Radford et al. Brain & Language 2014;129:43–6

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You can whisper without a larynx. "Patients who have undergone partial or full laryngectomy are typically unable to speak anything more than hoarse whispers, without the aid of prostheses or specialized speaking techniques." (source)

So the remainder of the vocal tract is capable of enough modulation to present typical human speech in many languages.

I expect, however, that the tongue, throat, jaw, and facial muscles figure very heavily into this modulation.

If these muscles become paralyzed or otherwise unusable, it's reasonable to assume that they may still be able to whistle with the use of the lungs and hands or fingers.

Hands free whistling, however, would require at least teeth and lips, or teeth and tongue, or lips and tongue - one surface to control the flow of air over the other surface that produces the whistle. With control over just these few things, one could likely communicate to a reasonable degree in many languages.

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Speech is generated by generating a frequency spectrum with the vocal folds, and then filtering it with the upper vocal tract. Whistling is done by blowing air over shaped tongue and lips.

So, give someone a laryngectomy. They still retain the upper vocal tract (and so can still whistle), but they cannot generate the source vibrations to speak. Do it as an adult and they probably understand the speech of others.

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It seems that speech can be recovered after total glossectomy, although it's not a short or an easy process.

Here's one case:

a case study, reporting the evaluation and evolution findings of the speech-language pathology rehabilitation of the swallowing and speech functions of a 58-year-old man submitted to total glossectomy in June 2009. After evaluation, the subject was diagnosed with severe mechanical oropharyngeal dysphagia and alteration in speech articulation. Speech rehabilitation used direct and indirect therapies. Indirect therapy focused on oral motor control, sensitivity, mobility, motricity, tonus and posture of the structures adjacent to the resected tongue. Direct therapy used the head back posture maneuver to help the ejection of food into the pharynx. The patient started exclusive oral feeding, except for solid foods, after ten months in treatment. Over-articulation, speed and rhythm exercises were used to improve speech intelligibility. Thus, the results of speech-language pathology intervention were considered positive, and the patient was discharged after a year in treatment.

Speech therapy in total glossectomy - case study, Vieira 2011

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