Sperm whale sounds are 'one of the closest parallels' in the animal kingdom to human language, a new study found.

While humpbacks sing hypnotic songs, sperm whales communicate through rhythmic clicks known as codas and scientists at Project Ceti have discovered that each click comes at a different frequency - like human vowel sounds.

Previous studies have focuses on the timing of their clicks to try to decipher their language, similar to Morse code, but this study departs from this idea and focuses on the frequency of the clicks themselves.

There are two click types - 'a' and 'i' vowels - that can be used at different pitches and even create diphthong double pitches (where one syllable is formed by the combination of two adjacent vowels), similar to languages like Mandarin.

Different whale pods were found to use different types of clicks, suggesting regional accents could exist in these marine communities.

University of California researchers attached small underwater microphones to 15 sperm whales for four years and computer analysis revealed a 'highly complex' linguistic system with similar patterns present in human speech.

Lead author, linguist at the University of California, Berkeley, Gašper Beguš, told Scientific American: 'On the surface, [these vocalisations] sound like this alien, ocean intelligence that has nothing to do with us. But when you actually look at it closely, you realise, 'Oh, we're way more similar.''

Analysis measured the sound waves and found a-vowels have a single distinct peak and i-vowels have two peaks.

These are similar patterns to those in human speech like Arabic which distinguishes between vowels based on their length. Delays in a vowel sound change the meaning of a word, as they seem to in sperm whales' language.

The findings were published in Proceedings of the Royal Society B. They suggest that whales have a 'highly complex' linguistic system which informs what type of click they make when communicating with each other.

Scientists speculate that the patterns of the clicking were 'highly suggestive' of language carrying meaning, though it is still shrouded in mystery.

'We demonstrate that sperm whale codas not only resemble human vowels acoustically but also pattern like them,' the study said. '[The patterns] have close parallels in the phonetics and phonology of human languages, suggesting independent evolution.

'Sperm whale coda vocalisations are thus highly complex and represent one of the closest parallels to human phonology of any analysed animal communication system.'

Whales are ancient creatures that descended from land mammals which shared a common ancestor with humans around 90 million years ago.

Sperm whales have the biggest brains of any species on Earth and can weigh up to 20lb - around