Robert Eklund, PhD, MA, BA

http://roberteklund.info

This site aims at summarizing what is currently known about (mostly) felid purring, i.e. the “trademark” sound produced by most species of cats, only excluding four or five of the biggest cats, the so-called “roaring” cats (lion, tiger, jaguar and leopard).

Purring.org is maintained by the (computational) linguist/phonetician/speech technologist/acoustician/musician (etc) Robert Eklund and information and sound files can be found at his other site http://ingressive.info or by clicking on the Wildlife button on his homepage.

Index

1 – A purring primer

The following text is basically lifted from Eklund, Peters & Duthie (2010), i.e. the paper presented at the Swedish Phonetics Conference at Lund University, 2–4 June, 2010, and is consequently co-written with Gustav Peters and Elizabeth D. Duthie, i.e.

Eklund, Robert, Gustav Peters & Elizabeth D. Duthie. 2010.
An acoustic analysis of purring in the cheetah (Acinonyx jubatus) and in the domestic cat (Felis catus).
In: Proceedings of Fonetik 2010, Lund University, 2–4 June 2010, Lund, Sweden, pp. 17–22.
[pdf]

The term ‘purring’ has been used liberally in the mammal vocalization literature, and an exhaustive review is given in Peters (2002). Using a definition of purring that continuous sound production must alternate between pulmonic egressive and ingressive airstream (and usually go on for minutes), Peters (2002) reached the conclusion that until then only ‘purring cats’ (Felidae) and two species of genets (Viverridae sensu stricto), Genetta tigrina, and most likely also Genetta genetta, had been documented to purr.

The subdivision of the Felidae, the cat family, into ‘purring cats’ on the one hand, and ‘roaring cats ’ (i.e. non-purring) on the other, originally goes back to Owen (1834/1835) and was definitely introduced by Pocock (1916), based on a difference in hyoid anatomy. The ‘roaring cats’ (lion, Panthera leo; tiger, P. tigris; jaguar, P. onca; leopard, P. pardus) have an incompletely ossified hyoid, which, according to this conception, enables them to roar but not to purr. On the other hand, the snow leopard (Uncia uncia, or P. uncia), as the fifth felid species with an incompletely ossified hyoid, purrs (Hemmer, 1972). All remaining species of the family Felidae (‘purring cats’) have a completely ossified hyoid which enables them to purr but not to roar.

However, there is no well-founded and unequivocal basis for a classification of the species in the family Felidae according to the absence/presence of purring and roaring, respectively, and differences in hyoid anatomy. Weissengruber et al. (2002) decidedly argued that the ability of a cat species to purr is not affected by the anatomy of its hyoid, i.e. whether it is fully ossified or has a ligamentous epihyoid, and that, based on a technical acoustic definition of roaring, the presence of this vocalization type depends on specific characteristics of the vocal folds and an elongated vocal tract, the latter rendered possible by an incompletely ossified hyoid.

The current classification of the Felidae is based on molecular characteristics (Johnson et al., 2006; O’Brien & Johnson, 2007) and groups the clouded leopards (Neofelis nebulosa and N. diardi) – with completely ossified hyoids – together with the five cat species in which it is incompletely ossified.

2 – Scientific papers

This section serves as a companion to the scientific papers that I and my co-authors have published on felid purring. Besides the papers proper, data files – sounds and video –  are found, as well as additional material.

2.1 – Fonetik 2015

Below you find the paper presented at the Swedish Phonetics conference in Lund on 8 June 2015. Nota bene! This paper is very much tongue-in-cheek, and should not be taken seriously but rather as entertainment.

Eklund, Robert. 2015.
Grimaldi’s “Discovery of the Cat Language”: A theory in need of revival (or perhaps not?) In: Proceedings from Fonetik 2015. Working Papers 55/2015, 8–10 June 2015, Centre for Languages and Literature, General Linguistics/Phonetics, Lund University, Lund, Sweden, ISSN 0280-526X, pp. 27–30.
[pdf]

2.2 – Fonetik 2013

Below you find the paper presented at the Swedish Phonetics conference in Linköping on 12 June 2013.

Plate 1 from the Fonetik 2013 paper. Cheetah breeder Pieter Kemp and Robert Eklund recording the male cheetah Mufasa at the Dell Cheetah Centre, Parys, South Africa.

Figure 1 from the Fonetik 2013 paper. Adult male cheetah Mufasa purring; Egressive and ingressive phases.

Film clip corresponding to Figure 1. The film clip shows egressive (breathing out) and ingressive (breathing in) purring phases produced by the male adult cheetah Mufasa. The voice-over during the first two phases is Robert Eklund saying out aloud the words “ut” (out) and “in” (in) with his hand on the cheetah’s chest in order to get an audio synchronization of egressive and ingressive breathing on the recording.

Figure 2 from the Fonetik 2013 paper. Subadult female cheetah Tippi purring; Egressive and ingressive phases.

2.3 – Fonetik 2012

Below you find the paper presented at the Swedish Phonetics conference in Gothenburg (Göteborg) on the 30 May, 2012. The film clip is not identical to Figure in the paper, but instead includes six (instead of four) breathing phases.

Eklund, Robert, Gustav Peters, Florian Weise & Stuart Munro. 2012.
A comparative acoustic analysis of purring in four cheetahs.
In: Proceedings from FONETIK 2012.
Gothenburg, Sweden, May 30–June 1, 2012, pp. 37–40.
[pdf]

Film clip illustrating the relative amplitude between pulmonic egressive (exhalation) and pulmonic ingressive (inhalation) phases in cheetah purring. Six phases are shown:
egressive–ingressive–egressive–ingressive–egressive–ingressive

2.4 – Fonetik 2011

The following video clips and sound files served as the basis for the Schötz & Eklund (2011) paper presented at the Swedish Phonetics Conference held at the Royal Institute of Technology, Stockholm, Sweden, 8–10 June, 2011. The paper can be downloaded below.

Observe that all film clips are available in high-definition, full-screen format.

Schötz, Susanne & Robert Eklund. 2011.
A comparative acoustic analysis of purring in four cats.
In: Quarterly Progress and Status Report TMH-QPSR, Volume 51, 2011. Proceedings from Fonetik 2011.
Royal Institute of Technology, Stockholm, Sweden, 8–10 June 2010, pp. 9–12.
[pdf]

Domestic cat recording sessions

Short excerpts from the recording sessions with the four domestic cats Donna, Rocky, Turbo and Vincent. Recorded by Susanne Schötz in her home (in Sweden). The recording dates are given in the film clips.

Please observe that all four film clips can be expanded to high-definition full-screen viewing.

Domestic cat sound files

Below you find sound files of purring produced by the four domestic cats Donna, Rocky, Turbo and Vincent (as shown in the videos above).

2.5 – Fonetik 2010

The following film clips and images were presented at the Swedish Phonetics Conference at Lund University, Lund, Sweden, 2 4 June, 2010. They are also partly included in Eklund, Peters & Duthie (2010), i.e. the paper published in the Conference Proceedings.

Below you find streaming film clips and high-resolution images of the figures in the paper, which can be downloaded below. Observe that all film clips are available in high-definition, full-screen format.

Eklund, Robert, Gustav Peters & Elizabeth D. Duthie. 2010.
An acoustic analysis of purring in the cheetah (Acinonyx jubatus)
and in the domestic cat (Felis catus).
In: Proceedings of Fonetik 2010, Lund University, 2–4 June 2010, Lund, Sweden, pp. 17–22.
[pdf]

Cheetah recording session

Short excerpt from the recording session with the (constantly) purring cheetah Caine. Recorded by camera operator Elizabeth D. Duthie and microphone operator, linguist Robert Eklund. Recording date: 5 December, 2009, at the Dell Cheetah Centre, Parys, South Africa.

Waveform and spectrogram analysis of a purring cheetah

A short film clip showing four phases of cheetah purring, clearly showing the difference between egressive (out-breathing) and ingressive (in-breathing) phases from an acoustic point of view. The phases shown are (in order): egressive–ingressive–egressive–ingressive.

Waveform and spectrogram analysis of a purring domestic cat

A short film clip showing six phases of domestic cat purring, clearly showing the similarity between egressive (out-breathing) and ingressive (in-breathing) phases from an acoustic point of view (especially compared to the cheetah). The phases shown are (in order): egressive–ingressive–egressive–ingressive–egressive–ingressive.

Waveform transitions egressive–ingressive phases in purring cheetah and domestic cat

A short film clip of waveforms showing phase transitions from egressive (out-breathing) to ingressive (in-breathing) phases in a purring cheetah (top window) and a purring domestic cat purring (bottom window). Not ‘stereo effect’ at the end of the clip.

Image files of waveform and spectrogram analyses

Below you find high-resolution image files corresponding to some of the film clips above. Click on the files, and high-definition images will open in new tab or window. Please observe that the spectrogram images below also include the first four formants, unlike the figures presented in Eklund, Peters & Duthie (2010).

Frequency ranges of purring in a cheetah and a domestic cat

Below you find the observed frequency ranges of the purring cheetah and the purring domestic cat described in Eklund, Peters & Duthie (2010), mapped onto an extended piano keyboard (the greyish octave to the left does not exist on modern pianos, but is added to the keyboard). The green colour indicates the frequency range of the purring, and the completely coloured key represents the mean value of the purring.

3 – Media interviews

3.1 – Press

Below is a list of my press appearances that discuss felid purring. Note that many of these are in Swedish.

Inside Your Cat’s Mind (September 2023; pages 54–61)
“What Does a Purr Mean. It Depends” by Mark Teich
Interviewed as a specialist on felid purring.

The Atlantic (7 September 2022; online)
“Purring Is a Love Language No Human Can Speak” av Katherine J. Wu
https://www.theatlantic.com/science/archive/2022/09/why-cats-purr-vocalization-science/671358/

Kattliv (2021, no. 6, pages 38–40)
“Kattutbildningar” [Cat education/courses] (Therese Lilliesköld);
Description of my course “Cat personality and communication”; see 08.01 Courses (selected).

Birkabladet (2019, no. 1, June, pages 12–14)
“Möt Robert Eklund – lingvist (språkforskare), musiker och kattälskare”
[Meet Robert Eklund – linguist (language researcher); musician and cat lover]
Researcher profile, cheetah studies, Meowsic.

Universitetsläraren (2018, no. 7, front cover and pages 14–18)
“Katter är ju bara bäst, snyggast och gulligast”
[Cats are just the best, the most beautiful and the cutest!];
Main article, researcher profile; my research in general, including music/musicology, speech technology, brain research, cats; also referred back to in the final issue Editorial, no. 8, 2018, page 2, when summarizing what that year’s articles have covered; Universitetsläraren [The University Teacher] is the union publication for Swedish academics.

Kattliv (2018, no. 5, pages 20–23 and 24–27)
“Flera har försökt knäcka språkkoderna” [Many have tried to crack the language codes] (Anette Rimönt);
“Kattens språkmelodier" [The language melodies of cats] (Lars Bergström);
Descriptions of Meowsic.

Svanslöst (2018, no. 1, page 2)
Meddelande om kommande föreläsning på Föreningen Pelle Svanslös Vänner
[Notification about coming lecture for the Friends of Pelle Svanslös Society] ("Peter Tail-less"; famous Swedish literary cat).

Aftonbladet Katt Special (14 November – 4 December 2017, pages 24–26)
“Jau seåg en rälig gnagarjävel” [In Scanian dialect: I saw an abonimable rodent bastard];
Description of Meowsic as well as my studies of cheetahs

Katzenmagazin (2017, no. 3, pages 28–29)
“Das Geheimnis des Schnurrens"[The secret of cat purring];
Interview on cat purring in general; photo of me with a caracal in Namibia.

Doktorn (2 December 2016)
“Forskare: Katter kan ha dialekt” [Researchers: Cat Might Have Dialects];
Description of Meowsic, cheetah and lion vocalisations.

Hela Gotland (17 November 2016)
“MJAU! Kan katter jama på gotländska?” [MEOW! Can cats meow in Gotlandish?]
Description of Meowsic, through TT.

Folkbladet (17 November 2016)
“Katter kan jama på dialekt” [Cats can meow in dialect];
Description of Meowsic, through TT.

Blekinge Läns Tidning (17 November 2016)
“Katter kan jama på dialekt” [Cats can meow in dialect];
Description of Meowsic, through TT.

Land (18 november 2016)
“Vilken dialekt jamar din katt på? Det undersöker forskare!”
[Which dialect does your cat meow in? Researcher are investigating this!]
Meowsic, cat vocalisations.

Västerbottens-Kuriren (18 November 2016)
“Katter kan jama på dialekt” [Cats can meow in dialect];
Meowsic, cat vocalisations.

Västervikstidningen (18 November 2016)
“Katter kan jama på dialekt” [Cats can meow in dialect];
Meowsic, cat vocalisations.

Värmlands Folkblad (18 November 2016)
“Katter kan jama på dialekt” [Cats can meow in dialect];
Meowsic, cat vocalisations.

Språktidningen (November 2016, no. 8, page 23)
“Spinnandets ursprung är ännu en gåta” [Purring origins still a mystery];
I explain cat purring. Part of a larger article “Pussy-cats meow exclusively to us” (pp. 18–24), on Meowsic.

Norrköpings Tidningar (8 maj 2016)
“Vad snackar din katt om?” [What is your cat talking about?];
Meowsic, cat vocalisations.

Motala Vadstena Tidningar (8 maj 2016)
“Vad snackar din katt om?” [What is your cat talking about?];
Meowsic, cat vocalisations.

Corren (3 May 2016, page 20)
“Vad snackar din katt om?” [What is your cat talking about?];
Meowsic, cat vocalisations.

Expressen (13 April 2016)
“Forskare ska reda ut: Pratar katter med dialekt?”
[Researchers are going to find out: do cats talk in dialects?];
Description of Meowsic.

Östgöta Correspondenten (5 april 2014, sidan 20)
“Han vill lösa mysteriet med spinnande kattdjur" [He wants to solve the mystery of purring felids];
Cat purring and general vocalisations, cheetah purring.

Våra Rovdjur (March 2014, no. 1, pages 18–21)
“Katten vad det låter!” [I'll be darned (Swe: "the cat!") how much it sounds!];
Cheetah purring and other vocalisations, wildlife conservation.