Cardinal vowels

The current system was systematised by Daniel Jones in the early 20th century,[1] though the idea goes back to earlier phoneticians, notably Ellis[2] and Bell.

This sound can be approximated by adopting the posture to whistle a very low note, or to blow out a candle.

These degrees of aperture plus the front-back distinction define eight reference points on a mixture of articulatory and auditory criteria.

This suggests a range of vowels nearer to forty or fifty than to twenty in number.

Ladefoged, in a series of pioneering experiments published in the 1950s and 60s, studied how trained phoneticians coped with the vowels of a dialect of Scottish Gaelic.

However, the most striking result is the great divergence of judgments among all the listeners regarding vowels that were distant from Cardinal values.