Abstract
Humans use whistled communications, the most elaborate of which are commonly called “whistled languages” or “whistled speech” because they consist of a natural type of speech. The principle of whistled speech is straightforward: people articulate words while whistling and thereby transform spoken utterances by simplifying them, syllable by syllable, into whistled melodies. One of the most striking aspects of this whistled transformation of words is that it remains intelligible to trained speakers, despite a reduced acoustic channel to convey meaning. It constitutes a natural traditional means of telecommunication that permits spoken communication at long distances in a large diversity of languages of the world. Historically, birdsong has been used as a model for vocal learning and language. But conversely, human whistled languages can serve as a model for elucidating how information may be encoded in dolphin whistle communication. In this paper, we elucidate the reasons why human whistled speech and dolphin whistles are interesting to compare. Both are characterized by similar acoustic parameters and serve a common purpose of long distance communication in natural surroundings in two large brained social species. Moreover, their differences – e.g., how they are produced, the dynamics of the whistles, and the types of information they convey – are not barriers to such a comparison. On the contrary, by exploring the structure and attributes found across human whistle languages, we highlight that they can provide an important model as to how complex information is and can be encoded in what appears at first sight to be simple whistled modulated signals. Observing details, such as processes of segmentation and coarticulation, in whistled speech can serve to advance and inform the development of new approaches for the analysis of whistle repertoires of dolphins, and eventually other species. Human whistled languages and dolphin whistles could serve as complementary test benches for the development of new methodologies and algorithms for decoding whistled communication signals by providing new perspectives on how information may be encoded structurally and organizationally.
Highlights
We argue that a better understanding of how information is acoustically encoded in human whistled languages, which may appear as simple non-linguistic calls when represented in spectrograms, can provide insights as to how information may be encoded in the whistled communication of dolphins and other whistling species
The cognitively complex and highly social dolphins have demonstrated a high level of complexity of their productive, computational, and perceptual capacities including their proclivity for vocal imitation and vocal learning, evidence for spontaneous combinatorial production of combined elements and behavioral concordance in their use, and comprehension of human generated grammatical “sentences. In this context, we suggest, based on what is known about the representation of complex information in human whistled speech, that more complex information may be encoded in dolphin whistled communication than previously thought and shown
Natural human whistled speech can be seen as a kind of intermediate for the analysis and decoding of dolphin whistles
Summary
Only a handful of species are considered to be vocal learners: cetaceans (Lilly, 1965; Herman et al, 1984; Reiss and McCowan, 1993; McCowan and Reiss, 1995a, 1997; Tyack and Sayigh, 1997), birds [passerines, psittacines (Todt, 1975; Pepperberg, 1981), and hummingbirds (Baptista and Schuhma, 1990)], bats (Esser, 1994), elephants (Poole et al, 2005), pinnipeds (Ralls et al, 1985; Stansbury and Janik, 2019), and some non-human primates (Snowdon, 2009; Lameira et al, 2013; Takahashi et al, 2015). In a human whistled language, the sender whistles syllables, words (Figure 1), and sentences (Figure 2) of the native human language, transposing spoken modal speech into a very different acoustic form to enable long distance dialogues as modulated whistles augment speech with properties of a real telecommunication system. Some species of birds, anurans, insects, and mammals produce songs that use the same bands of frequencies as human spoken and whistled speech, but they are much more intermittent, seasonal, and/or more biotope specific (Meyer, 2020)] These properties define a real telecommunication system adapted to natural acoustic conditions that enables interlocutors to speak from far with birdlike sounds at distances typically going from around 50 m to 2 km depending on the place, with common median uses of 400–500 m. /e/ and /a/), whereas the second speaker says /ben.a/ with a clear pause between /en/ and /a/
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