 Hi, I'm Suzanne Schütz and I was very happy to receive the 2021 Ig Nobel Prize for Biology. I'm a researcher of phonetics which means that I normally study human speech but I've also studied the vocal communication of domestic cats. In this informal lecture I'll try to explain what I did and why I did it and I'd like to start by playing this video. Did you notice that the cats in the video apart from meowing also used other sounds or call types? They trilled and chirruped, they growled, howled, hissed, snarled, cried, chirped, chattered and purred. Now cats produce and articulate these call types differently. They contain different vowel and consonant-like sounds and the pitch, melody and voice quality is also different so they sound different from each other. If you like me, share your home with one or more cats. You may have wondered what the different sounds mean because if I become better at understanding their communicative signals I may improve our relationship and increase the welfare and well-being of my cats. When I read books and articles about cat communication I could only find a few descriptions of their vocal signals and the ones that I've found either described only one or a few different call types or were based on a small number of cats. So I recorded and analysed the sounds of my own cats and of other cats using the same phonetic methods that I used to study speech. I was interested in how cats sounds are produced and articulated, what the acoustic properties are like the frequency distribution of the sound energy, the length or duration, the fundamental frequency or pitch and the intonation or melody patterns and I was also interested in how humans perceive these sounds. I listened carefully to the different types of sounds that my own and other cats used in different situations and using the existing descriptions as a starting point I tried to describe the different sounds phonetically and I analysed their acoustic features and I categorised them. I also tried to write them down using a phonetic alphabet. This table summarises my results. It lists the different sound types that I've identified so far. As you can see there are quite many different types so I'd like to give you a few examples. I'd like to start by showing you two subtypes of trilling, chirping and granting. Now trilling is a very friendly sound it's produced with the mouth closed and it's voiced and it has sort of pulsating vibrations. You can see that in this diagram here which is an oscillogram that these regular pulses occur and you can also see them in the next diagram here which is called a spectrogram which shows the sound energy distribution in various frequency bands or frequency areas so the darker the more energy so we have a dark band here with much energy and you can see the pulses again and then there are lighter areas with less sound energy and then there's a dark band again around 4000 hertz and the next one around 6000. At the bottom we have the fundamental frequency the pitch contour it rises towards the end and it's fairly high pitched. Now the grant also has these vibrating pulses but the sound energy is concentrated in the very low frequency area around 1000 hertz and the pitch contour is much lower and it's more level so this is a grant. I'll play you the cheer up in the ground so you can listen for yourself and see if you can hear these differences. This is the cheer up and this is a grant. The next sound I want to show you is the growl. Now the growl is a warning sound produced with the mouth closed or slightly open and it's voiced and it's very long as you can see here and it sounds creaky or harsh and it's very dark and low pitched and the top one here is produced entirely with the mouth closed it's long and regular pulsating you can see each of the pulses of the vibrations in the spectrogram and you can also see that the energy is almost entirely concentrated below 1000 hertz so it's really dark and low and the fundamental frequency the pitch contour is also a bit rough now the lower one is produced with the mouth slightly open so the acoustics are slightly different there's more energy in higher frequencies where the mouth is open but again the fundamental frequency is level and rough like this and I'll play you these two examples first the one with the mouth closed sounds like this and the lower one you can look at his lip his curling up his lip in the beginning of the sound sounds like this the next sound I want to show you is the hiss. Now the hiss is also a warning sound but it sounds completely different from the growl and that's because it's produced articulated differently. The hiss is produced with the mouth held tensely open the teeth are showing and it has no voice it's voiceless instead there is audible noise of varying color and I'm showing you two different hisses here the top one is brighter in color it has more energy in the higher frequencies whereas the bottom one has its energy at lower frequencies and so it sounds a bit darker I have only one video of a cat hissing to show you but I will play you the lower one to show you the difference between the two sounds so listen carefully now this is the top one and the bottom one the final sound I want to show you is purring now purring is produced with the mouth closed most of the time and it's produced both during inhalation and exhalation so it can go on for minutes at a time it's very soft and of course extended it's breathy and it's a regularly vibrating sound at around 20 hertz and cats don't only purr when they are happy they also purr when they are hungry stressed in pain and I have two diagrams of purring here the top one you can see clearly the two phases this is the inhalation phase and then we have the exhalation the inhalation the exhalation and you can see the phases in the spectrogram as well but most of the sound energy is at very low frequencies and you can see that the fundamental frequency is around 20 hertz now the bottom one is actually a variant of purring where there's some trilling going on as well so this is the exhalation phase where we have the trill you can see the pulses resembling the trill then we have an inhalation phase which is softer in this case and then we have a trill again which is merged with purring and then again the inhalation phase I'll play you these two so you can hear the difference between them starting with the top one and then the bottom one so the domestic cat has several phonetically distinct sound or call types and there is also quite a large variation within each type depending on the individual cat just like human voices differ between individuals and on the situation or context on the mood or mental or emotional state of the cat and you can find this variation in the length of the sound the loudness in the pitch and melody and also in the voice quality if you want to learn more about how cats vary their voices and what their different sounds mean you could check out my book the secret language of cats which is available in several languages you can also find descriptions of and listen to more examples of cat sounds on our project website meowsic.se thank you for listening or perhaps I should say