Let's assume you already know what you want to say. Then, all you need to do is to broadcast your thoughts as sound waves using a suitable “air wave creating device”. Luckily you were born with one of those devices built into your neck. It is known as a larynx. Here you can see a little movie of a larynx in action.

Question: can you work out what changes in the larynx to make some sounds high pitched and others not?