Cat purr
...Cats purr at a frequency of 26 Hz. Purring frequency for individuals does not change with age. Purring can occur simultaneously with other vocalization. The primary mechanism for sound and vibration production is a centrally driven laryngeal modulation of respiratory flow. The diaphragm and other muscles appear to be unnecessary for purring other than to drive respiration. Frazer-Sissom, Dawn E., D.A. Rice, and G. Peters. How cats purr. Journal of zoology: proceedings Zoological Society of London, v. 223, January 1991: 67-78.
...It was thought that the purr was produced from blood surging through the inferior vena cava, but as research continues it seems that the intrinsic (internal) laryngeal muscles are the likely source for the purr. The laryngeal muscles are responsible for the opening and closing of the glottis (space between the vocal chords), which results in a separation of the vocal chords, and thus the purr sound. Studies have shown, that the movement of the laryngeal muscles is signaled from a unique “neural oscillator” in the cat’s brain. http://www.loc.gov/rr/scitech/mysteries/catspurr.html
...One hypothesis is that cats produce the purring noise by vocal cords twitching of the muscles in their larynx, which rapidly dilate and constrict the glottis, causing air vibrations during inhalation and exhalation. Combined with the steady inhalation and exhalation of air as the cat breathes, a purring noise is produced.
...Feline purring has previously been reported as originating in a central oscillator, independent of afferents inputs, and also as not involving expiratory muscles. Here we show that expiratory muscles can be involved and that even if the oscillator is central, reflex components nevertheless play a considerable part in the production of the periodic pattern of muscle activation seen during purring.
this one +Remmers, J.E. and H. Gautier. Neural and mechanical mechanisms of feline purring. Respiration Physiology, v. 16, December 1972: 351- 361.
...we report how domestic cats make subtle use of one of their purring to solicit food from their human hosts, apparently exploiting sensory biases that humans have for providing care. When humans were played purrs recorded while cats were actively seeking food at equal amplitude to purrs recorded in non-solicitation contexts, even individuals with no experience of owning cats judged the solicitation purrs to be more urgent and less pleasant. Embedded within the naturally low-pitched purr, we found a high frequency voiced component, reminiscent of a cry or meow, that was crucial in determining urgency and pleasantness ratings. Moreover, when we re-synthesised solicitation purrs to remove only the voiced component, paired presentations revealed that these purrs were perceived as being significantly less urgent. http://www.cell.com/current-biology/abstract/S0960-9822(09)01168-3
http://www.lifesci.sussex.ac.uk/cmvcr/Publications_files/McCombetalPurring.pdf
I hoped to find WHY do they purr. It is not even known HOW are they doing it. And we are talking about the most familiar animals: CATS.
...It was thought that the purr was produced from blood surging through the inferior vena cava, but as research continues it seems that the intrinsic (internal) laryngeal muscles are the likely source for the purr. The laryngeal muscles are responsible for the opening and closing of the glottis (space between the vocal chords), which results in a separation of the vocal chords, and thus the purr sound. Studies have shown, that the movement of the laryngeal muscles is signaled from a unique “neural oscillator” in the cat’s brain. http://www.loc.gov/rr/scitech/mysteries/catspurr.html
...One hypothesis is that cats produce the purring noise by vocal cords twitching of the muscles in their larynx, which rapidly dilate and constrict the glottis, causing air vibrations during inhalation and exhalation. Combined with the steady inhalation and exhalation of air as the cat breathes, a purring noise is produced.
...Feline purring has previously been reported as originating in a central oscillator, independent of afferents inputs, and also as not involving expiratory muscles. Here we show that expiratory muscles can be involved and that even if the oscillator is central, reflex components nevertheless play a considerable part in the production of the periodic pattern of muscle activation seen during purring.
this one +Remmers, J.E. and H. Gautier. Neural and mechanical mechanisms of feline purring. Respiration Physiology, v. 16, December 1972: 351- 361.
...we report how domestic cats make subtle use of one of their purring to solicit food from their human hosts, apparently exploiting sensory biases that humans have for providing care. When humans were played purrs recorded while cats were actively seeking food at equal amplitude to purrs recorded in non-solicitation contexts, even individuals with no experience of owning cats judged the solicitation purrs to be more urgent and less pleasant. Embedded within the naturally low-pitched purr, we found a high frequency voiced component, reminiscent of a cry or meow, that was crucial in determining urgency and pleasantness ratings. Moreover, when we re-synthesised solicitation purrs to remove only the voiced component, paired presentations revealed that these purrs were perceived as being significantly less urgent. http://www.cell.com/current-biology/abstract/S0960-9822(09)01168-3
http://www.lifesci.sussex.ac.uk/cmvcr/Publications_files/McCombetalPurring.pdf
I hoped to find WHY do they purr. It is not even known HOW are they doing it. And we are talking about the most familiar animals: CATS.