The loudest purr in the world

January 15, 2013 • 1:38 pm

So you think your cat has a good purr? Now THIS is a purr:

The YouTube notes give details:

Most domestic cats purr at around 25 decibels but Merlin has hit a mog-nificent 100 – louder than a hair dryer, a hand drill or a lawnmower. The 12-year-old pet is so noisy owner Tracy Westwood struggles to hold telephone conversations or hear the TV. Mrs Westwood, 47, said: “I often have people asking me what on earth is the noise in the background – it’s just Merlin the cat.” Mrs Westwood, a tarot card reader from Torquay, Devon, took in Merlin when he was just a kitten from an animal rescue centre.

Here’s a decibel scale from the California Department of Transportation. Sitting next to Merlin is between having your Walkman at the highest level and being at the front row at a rock concert!

Picture 1

h/t: Su

23 thoughts on “The loudest purr in the world

    1. Good fit! Wonderful engines. The P-51 had a 12 cylinder in line Rolls Royce Merlin also. My favorite though was the 24 cylinder in line built for the XP-70.

      I once went to a tractor pull competition many years ago. To my surprise I had a great time. The show stopper was a tractor in the unlimited class called Double Ugly. A home made square tube steel rectangular platform with two little wheels up front, two very large wheels in back, and a Rolls Royce Merlin 24 cylinder in line engine in between. The owner claimed it produced 6000 hp, and I believe it. The driver, looking rather tiny, sat on what appeared to be a riding lawnmower seat on a high mount right behind the engine over the rear axle. No body work of any kind, strictly utilitarian. The engine block had the name spray painted on it graffiti style in white paint. All the other tractors in the class had tens of thousands of dollars of bling and engineering put into them. When Double Ugly managed to start his engine, after the third try, purple flames at least 20 feet long shot out of the two vertically mounted collector pipes, and it was so loud that in a stadium of 80,000 you couldn’t hear yourself scream. He then knocked out a full pull, and was still accelerating when he crossed the line. He actually had to use his brakes to keep from running through the end of the stadium. None of the fancy high dollar tractors even came close.

      1. I think you’ll find that the RR Merlin was a V12, not in-line. I am unaware of a 24 cylinder version, but I think a 24 cylinder in-line engine is very unlikely.

        1. Rolls-Royce Merlin III Specifications

          Type: Inline liquid-cooled internal combustion engine.

          Configuration: 12-cylinder 60-degree upright vee.

          Valve train: Overhead camshaft-actuated, 48 valves, sodium-cooled exhaust valve stems.

          Fuel system: Updraft carburettor with automatic mixture control.

          Oil system: Dry sump with one pressure pump and two scavenge pumps.

          Cooling system: Pure ethylene-glycol cooling mixture, unpressurized.

          Supercharger: Single-speed, single stage.

          Bore: 5.4 in (137.3 mm)

          Stroke: 6 in (152.5mm)

          Capacity: 1,648.96 cu in (27.04 l)

          Compression: 6:1

          “In line” refers to the engine “type,” not the “configuration.” “Straight” is the common term for the configuration of all cylinders lined up in a straight line.

          Rolls Royce, Allison, and maybe others as well, all made 24 cylinder air craft engines in various configurations (X, H, etc.) during the WW II era. I did mistakenly call the one in Double Ugly a “Merlin,” which is a specific type of Rolls Royce engine, and technically it was not. The engine in Double Ugly was a very rare experimental engine for an experimental fighter aircraft and they were both cancelled before They ever made it to production because WW II ended. If I recall correctly there were only 2 test aircraft produced, not sure how many engines, but not many. I remember reading a book of experimental aircraft from that era that described the engine in Double Ugly to be “basically two Merlin engines end to end.”

          1. I stand corrected, having misread “inline” as meaning straight. This is the normal nomenclature for car engines, which are my area, but I now realise that inline in aircraft nomenclature means “not radial” (a configuration less common in cars :-)).

  1. I’m never sure what one can make of these sorts of decibel scales. Take “military jet takeoff” – from what range is that measured? Edge of the airfield, edge of the runway or edge of the tail fin? Without that sort of information the figures don’t seem to mean anything at all.

    And my very limited experience of rock concerts would definitely place them above the pain threshold, not below it.

    1. Yes. The purr was loud — but louder than a lawnmower? A lawnmower heard from what distance?

      To me, Merlin’s purr seemed about as loud as a human voice speaking at normal pitch — his owner’s voice, perhaps. I doubt very much that she is louder than a lawnmower. It’s a pity she didn’t hold the monitor right up to her lips and say something, for comparison.

    2. Yeah, I don’t get that either- I have to wear earplugs to most concerts if I’m sitting near enough to the stage to tell what the band is wearing (good hearing, terrible vision).

      1. I’d be glad to, provided you send me the requisite equipment for making a web-compatible recording of her purr. Meanwhile, please explain first of all, how a picture can portray a purr and, secondly, how I can upload a picture from my hard drive to a comment. It’s up to you.

  2. Oh, no a plane is taking off in Chicago. I can’t hear myself think. Now one is taking off in Melbourne. When will it stop?

    Describing a sound requires 2 (two) numbers:
    – intensity
    – distance

  3. “The distance of the measuring microphone from a sound source is often omitted when SPL measurements are quoted, making the data useless.” [Wikipedia]

    The standard distance is 1 m.

  4. Before I watched the video I thoought to myself, “no way” could a cat purr that loud. I am wrong.

    Also, from some of the comments it seems there is the misunderstanding that the decibel scale is linear. It is not. It is based on a logarithmic scale. Increasing sound “intensity by a factor of 10 raises its level by 10 dB; increasing it by a factor of 100 raises its level by 20 dB; by 1,000, 30 dB” and so on. So you can see that a loud purr is a far cry from front row at a concert or jet taking flight.
    If the very rough reference chart at the top were accurately depicted there would not be enough page space to represent the difference between 100db and 130dB.

  5. I could be wrong about this because I heard about it so long ago.

    The purring mechanism in a cat’s throat is a vibrating valve that allows air to pass through it. I works, and sounds, the same whether the cat is inhaling or exhaling. Try this on your own cat to test it.

    Whereas, the meowing voice of a cat seems to work only when the cat(like our voices) is exhaling.

    The cat in the video has a much louder purr on the exhale. This makes me wonder if the cat is engaging its meowing voice when it’s exhaling.

    If this is the case then perhaps this example may not qualify as a purr, strictly speaking.

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