The Larynx is positioned in the top of the trachea. Primarily it is a valve which regulates respiration, but additionally it is a sound source. The larynx houses the vocal folds which open and close. As you might guess, the larynx and vocal folds are very complex structures – a delicate web of bone, cartilage, muscle and ligament. The vocal folds themselves are made up of separate loose bands of muscle, that can move over each other to allow high speed vibration.
Here we massively simplify the structure of the vocal folds, and represent their movements in terms of just two sub-parts: the ligamental folds and the arytenoids. These are labelled in the graphic, and we’ll refer to these parts in describing the different phonation modes. For now, note that these two sub-parts of the folds can move in unison (ie. both open), or differently (eg. for whisper, the ligamental folds are closed, but the arytenoids are open).
The vocal folds can be very hard to see clearly for a number of reasons;

• they vibrate too fast
• the entire larynx bobs up and down
• the false vocal folds, epiglottis, and pharynx walls all contract and obscure the view

So our approach throughout this section is to show you some real video footage, but to also combine it with animations which represent a highly idealised view of vocal fold movement.

Before looking at the vocal folds in speech, let’s see the position of the folds for normal breathing, and lifting.

The vocal folds are held far enough apart during breathing to allow easy unimpeded airflow.

Play the top video to see the position of the folds during normal breathing (actually rather heavy breathing!). Note that both the ligamental folds and the arytenoids contribute to creating a large opening.

In a sense your vocal tract is an opening into your chest. However the chest needs to be closed to be structurally strong. The vocal folds also play a crucial role in providing the closure that gives the upper torso the structural integrity it needs to lift heavy objects, defecate, and cough.
Play the 2nd video to see how the folds close up. Note that this is not just light closure of the vocal folds as you would see for a glottal stop. Rather the closure you see here is the heavy closure of both the vocal folds and the false folds that you make when you strengthen your chest to pick up a heavy object.