It’s official: Smokey is the world’s loudest cat

May 9, 2011 • 11:30 am

About five weeks ago Matthew Cobb posted an item here about Smokey, a British cat reputed to have the world’s loudest purr.  Well, it’s just now been made official: the Guinness Book of World Records has recorded Smokey at an astounding 67.7 decibels, making her the holder of the title for Loudest Purr by a Domestic Cat.  That noise, sixteen times louder than the average purr, is roughly equivalent to the sound of a vacuum cleaner, right at the threshold of “annoying loudness.”

How loud is Smokey? Have a listen:

A funny MSNBC piece, including an interview with both Smokey and her owner, is here.

The Guinness site helpfully compares this to other animal sounds:

The loudest animal sound is the low-frequency pulses made by blue whales (Balaenoptera musculus) and fin whales (B. physalus) when communicating with each other. These whales reach an amazing 188 dB on the decibel scale, creating the loudest sounds emitted by any living source. Total silence is 0 dB, a lawnmower – 90 dB, car horn – 110 dB, – a rock concert — 120 dB. Blue whales and fin whales are louder than all of these!

Congratulations, Smokey!

19 thoughts on “It’s official: Smokey is the world’s loudest cat

  1. No, Guinness, 0dB is not total silence. It’s approximately the faintest sound that a human can hear. (Why do so many people struggle with logarithms?)

    1. Good catch! At some frequencies, many people have hearing thresholds less than 0 dB SPL (sound pressure level, referenced to 20 uPa).

  2. When I first met the information about fin whales and their 180db+ vocalizations, I had recently also read a piece about sound-based weapons. Apparently, some prototype and experimental weapons have produced sounds as loud as 200db, which is sufficient to quickly kill a person. The article about weapons described 180db as about the point at which sounds are lethal to humans, with severe tissue damage starting a bit quieter, around 160db.

    How does a fin whale avoid shredding it’s own skin when blasting out that signal? Does it have something to do with the way sound interacts with (squishy wet) mammalian tissue in air vs. underwater?

    1. I had to go and refresh my memory on this, but sound pressure levels in air and water are not easily comparable. As an SPL is a logarithmic quantity, you need a reference pressure to measure against. These are different for all sound media.

      To put it in perspective, the threshold of hearing for a diver (according to wikipedia – see underwater acoustics) is around 67 dB.

      An SPL of 188dB in air would be horrific (and very likely fatal).

      Not sure if that answers your question…

    2. When measurements of Sound Pressure Level (SPL) are expressed in decibels (dB), the numerical values for underwater sound tend to look huge for two reasons.

      One factor is that SPL in air is typically referenced to 20 uPa, while SPL in water is usually referenced to 1 uPa. And because decibels in general go as 10*log10() for ratios of power, or 20*log10() for ratios of amplitudes, then equal SPL in air and water would be reported higher underwater by 20*log10(20uPa/1uPa) = 26 dB.

      But a much more significant factor is that water is much more dense and stiff than air. So if a cat (in air) and a whale (underwater) would radiate the same power in Watts (hypothetically), the cat would generate much lower pressure and higher particle velocity, while the whale would generate much higher pressure and lower particle velocity. For argument, if we reported particle velocities instead, I bet a real cat could boast bigger numbers than a real whale (even though I bet a real whale generates more Watts).

      These different metrics cause confusion when we care about protecting marine mammals from noise. Shipping and sonar may disturb migration and cause physical harm. But the public sees huge dB values of SPL underwater and can’t judge intuitively what levels would be harmful. For this reason, some underwater acousticians have argued for reporting underwater sound levels in dB relative to Watts (for the strength of a source) and Watts per square meter (for sound at a distance).

      A more general point to take away is that decibels express ratios (as logarithms of ratios), so decibels are always defined “relative” or “re” some “reference” value (to give logarithms dimensionless arguments).

      1. Yep, Dave said it better than I.

        An additional factor to consider is the way we hear things. Smokey’s measurement was apparently recorded as an L_A peak, meaning that the final peak reading was adjusted using an a-weighing scale. This scale is often applied to noise measurements to make them more closely match the way the human ear hears – in short, low and high frequency sounds are penalized, as we don’t hear them as ‘loud’ compared to other frequencies.

        The whale noise is not given in this scale, so you can’t compare it to smokey. An a-weighting for water borne noise wouldn’t apply or make sense either – have you ever tried to listen to yourself talk underwater?

  3. “Total silence is 0 dB …”

    Nonsense. If total silence were 0dB then 67.7dB would be perfectly silent as well.

  4. We had a Burmese cat named Boris (his female littermate, our other cat at the time, was Natasha) who could purr louder than any other cat I’ve heard. Boris and Natasha slept with us humans in bed, and to touch Boris in the night was to invoke the sound of a boat’s outboard motor at close range.

    Alas, Boris died at a relatively early age; he got out and was treated terminally roughly as a playtoy by the neighbor’s dog. His sister Natasha exhibited more respect for the forbidden outdoors and died only this last January at a venerable 19 years of age. Ceiling Cat bless them both.

  5. I’m just fervently hoping all this hullabaloo about animal sounds doesn’t now extend to contests measuring other bodily functions, which shall remain nameless.

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