Did You Know: A Rotary Subwoofer can Reproduce a Tiger's 18 Hz Roar


It is a commonly held belief that the frequency response of human hearing is between 20 Hz and 20,000 Hz, with degeneration of the upper frequencies occurring as a person grows older. More recent research may indicate that human beings can detect signals much higher than this, though the perception of those frequencies may be expressed as harmonic interactions and by the transient crossings in the time domain. But what about experiencing sounds below 20 Hz?

"New technologies such as the remarkable rotary subwoofer now make this possible..."

Generally, it’s understood that human beings can’t detect sounds below 20 Hz, which is why the stated frequency response of many products is from 20 to 20,000 Hz. Part of this impression comes from the challenges in using traditional cone and voice coil subwoofers to produce these frequencies at sufficiently high levels. New technologies such as the remarkable rotary subwoofer now make this possible, and human beings can, in fact, feel and be affected by these infrasonic frequencies.

In nature, infrasound is common. Elephants can trumpet to one another, and whales can communicate at great distances by generating these tones. One infrasonic frequency of particular interest is centered around 18 Hz and is generated by the unusual shape, stretch, and shear-ability in the folds of a Siberian tiger’s vocal chords.   

Based on studies by bio-acoustic specialist Dr. Elizabeth Von Muggenthaler, of the Fauna Communication Research Institute, and Edward J Walsh of the Boys Town National Research Hospital, tigers have been observed to emit growls and roars for a variety of reasons such as: marking territory, attracting mates, and scaring off rivals. They can generate sounds as loud as 114 dB in the audible spectrum, but the tone at 18 Hz is interesting because the combination of the infrasonic tone with the roar within the higher spectrum may cause momentary paralysis to animals within earshot. 

As if it weren’t enough that tigers can jump more than 30 feet, they may also be equipped with this infrasonic stun gun.      


Unfortunate that there are so many idiots with hunting rifles, but there is a solution to their stupidity, take your hunting rifle to B & H (without ammunition) and with only 20,000 US dollars, take a Nikon D5 XQD and Nikon Lens 600 mm, must be buy accessories separately. and you can put beautiful pictures of tigers in your house, and you'll be proud of us all, also magically stop being stupid and QI will rise many points. (if you buy Canon, the QI does not rise)

It is a joke and take it like it is

stop killing wild animals, go to the supermarket and buy a chicken.

forget an important point leaves the rifle in the trash

While I am a liberal person who does not own a gun and does not hunt, I would surmise there are probably 500 illiterates with a dopey ax to grind for every tiger hunter. In fact hunting does more for sustaining rare animals like tigers than you will ever do via ignorant insults, because the permitting and fee system is the basis for animal protection in Africa. Grow up, learn the facts, and realize that your stabs at people doing things you do not like are just worthless self-massage.

Sorry. Tigers do live in Asia. Especially the so-called Siberian tiger. This critter lives on the Russian side of the Amur River [possibly it crosses into China] if they haven't all been killed by idiots.

It was a lion. Tigers live in Asia, not Africa. Unfortunately for us all, under the laws of Zimbabwe (where the lion was shot), it was legal.

so let's hear this and a real tiger in a blind a/b and see which one the dentist shoots at.... that's how you know if it's any good. SCIENCE! Not hype.

LOL, I am really surprised that there is only one comment referring to that recent news story.

Not "vocal chords, but "vocal cords."  Actually, vocal folds is a better descriptive term.  Why "vocal chords"?  Maybe because the term has to do with sound, and so do chords?


Bennet, while they are short on specifics, I believe they are referring to the fan type model, which is the TRW-17 Thigpen Rotary Woofer by Eminent Technology http://www.rotarywoofer.com/  - As you mentioned it looks and rotates like a fan, but the blades pitch back and forth, creating extreme SPL at ultra low frequencies - Demo from AudioEngineering Society Convention with a laser across the blades shows huge deflections. I've not heard it either but has apparantly been used in big instals at Niagra and other locations, looks very intersting

The servo drive models you referred to I experienced firsthand in the early 90's, specifically the SDL7 by Intersonics   As mentioned, they used a servo motor that drove a belt that pushed and pulled pistons attached to cone drivers, essentially replacing the magnet & voice coil with this servo-driven mechanism that allowed for much greater excursions, providing not only much greater output with less power, but also more precise control / damping factor for "tighter" punchy bass.  We did a shootout with a bunch of pro subs from JBL, Meyer, Apogee and other major concert PA manufacturers and the SDL walked away from with a fraction of the power.   Like the tiger thing, they made a smaller box that was used in elephant communication research

I recently read about what appears to be an modern update of the servo-drive concept, the M-FORCE Moving Magnet Linear Motor Transducer, which I understand uses a magnetic mechanism to drive the piston, providing even more control & reducing distortion by eliminating the inertia of a conventional motor.  Again have not heard it, but can definitiely see the potential for both this and the rotary type to open up new realms of capabilities....

Nice tiger photo.

Hi All

The "rotary" part of the subwoofer is not the cone, or cones, as in a Leslie speaker designed to produce a vibrato.  For a rotary drive subwoofer, the motor/driver is not a linear voice coil type motor, but is a rotary servo-motor.  It is linked to conventional linear oscillating speaker cones using a rotation to linear transmission (usually a belt drive).  This mechanism was invented by Tom Danley about 30+ years ago.

We needed some subs that would reproduce the sound of wind turbines in the 1980's.  Danley was going to build them.  Unfortunately, that project did not happen.  However, Danley built another huge subwoofer, the Matterhorn.

Another inventor came up with a rotary fan, with wiggling blades that claims very low frequency response.  Have not heard it ~ $13,000.

Best wishes

Bennett Brooks

Hey guys the vibrate function in the phone your commenting with, is a rotary speaker. If you compare it to a Leslie you are missing the point. 

For those who doubt: you must hear these sub woofers to become a believer as happened to me. I too am from the generation where "rotary" meant Leslie. I think the this new invention chose the name without giving much thought to any repercussions from history but if you want technical information about these sub woofers and why they are so amazingly GREAT check the web sites of Marshall & Ogletree or Cameron Carpenter. I was fortunate to hear Mr. Carpenter at Stony Brook NY in January and these speakers performed exactly as reported. I'm no engineer (I'm a musician) but as I understand it, they create this amazing low frequency sound with a tiny fraction of the amplifier energy required to create the same sound with an "old fashioned" standard sub woofer cone and magnet set up. The rotary function is many times faster than the Leslie speaker, affects only the lowest notes and the speed of the rotation is dependant on the pitch wave being generated and thrust into the room creating the non directional low notes of the most powerful 32 foot organ pipes. Until these sub woofers, the wimpy low end was always the dead give away of a non accoustic pipe organ. Now you really can't don't hear that weakness.  

Zoet, the rotating horn in a Leslie does not "distort the wave by making it pulse."

Its change of the sound is the result of the Doppler effect, where the pitch of the sound increases when the open end of the rotating horn is moving towards you and the pitch decreses when it is rotating away from you.

A police car siren is a familar example of the Doppler effect. The pitch of the siren is suddenly lower after the car passes you.

This happens because the wavelength is effectively lengthened when the source is moving away the listener, and vice versa. Longer wavelenths are percieved as lower pitch.

There's absoslutely no evidence that humans can perceive well above 20KHz.  You might find a young child who can hear 22KHz, but that's about it.   All this talk about "though the perception of those frequencies may be expressed as harmonic interactions and by the transient crossings in the time domain" is gibberish.    

In the early 1960's, there was a company making hi-fi speakers that rotated (aside from the Leslie Tone Cabinet).   I remember seeing them at an audio show.  I believe they were called "Circle-o-phonic" or something of the sort.   I was only 12-13 at the time and I thought they sounded fantastic,  but the reality is that they probably sounded terrible, especially for stereo.    They probably had all kinds of phase problems.  I don't remember them ever being marketing at retail. 

While the rotating speaker in the Leslie Tone Cabinet gives the Hammond B3 a fuller sound, it also distorts the wave by making it pulse.    That's fine for an effect, but it's not fine to accurately reproduce waveforms.   Without a further explanation, I fail to see how rotating a speaker would increase its frequently response.   Either the speaker cone can reproduce 18 Hz or it can't.    Even the theatrical systems that tried to reproduce low frequencies at high levels like Sennsurround, which was used for the movie "Earthquake" (and actually caused damage to some theaters) did not use rotary subwoofers.   

18Hz might stop an animal in its tracks, but physically paralyzes another animal that's also capable of reproducing it?    Is this "The Onion"?  What a bunch of hype!

Circle-o-phonic? Were you thinking of the old Zenith Circle of Sound speakers? They had the speaker mounted horizontally in the bottom pointing up at a cone pointing down to theoretically distribute the sound 360 degrees. But nothing actually rotated AFAIK. 

I seem to remember some years ago attending a lecture with the venerable Rupert Neve who was just returning from a study in Japan where they had proven that whereas we do register those ultra high frequencies as perceivable sound we do, in fact, register them in other ways as 2nd and 3rd order harmonics and alter our perception of the sounds we actually do register . That being said if  I heard a tigers roar, subsonic or other  I'm pretty sure I be paralysed with fear and a need to change my underwear.

Hi ZoetMB,

Thank you for sharing your anecdote about hearing a pair of Circle-O-Phonic speakers. From time to time I have seen them available on EBAY, so it would be interesting to find a pair and compare the sound to the latest and greatest speaker systems available as well as your memory of how they sounded back in the 1960's.  Who knows, maybe they do sound as good as you remember...  

As was mentioned above, the Thigpen rotary subwoofer does not have a speaker cone, but rather a constantly spinning five-bladed fan that uses pitch adjustments of the fan blades to generate low frequency waves.  It's a rather specialized technology that the majority of people haven't yet been exposed to yet. I imagine this will change as it becomes more readily available and more of us can share in the experience of super low sound.    

The commonly held notion that the frequency response of human hearing is from 20 Hz to 20 kHz is often based on the results of typical audiometry or hearing tests- those times in elementary school where a technician plays a tone and you raise your hand if you can hear it or not.  These tests don't really represent the full picture though because our hearing systems didn't evolve to register pure tones, but rather complex interactions of multiple frequencies and their harmonics in time.  

To better understand this point, I refer you to the following technical paper by David E Blackmer, the brilliant mind behind the truly exceptional line of Earthworks Microphones and Preamplifiers. 

.  http://www.earthworksaudio.com/wp-content/uploads/2012/07/The-world-beyond-20kHz.pdf

It should help clarify the cognitive processes by which the brain detects, perceives, and interprets a sound as well as the relationship between frequency response and the time domain (which you can calculate using a Fourier transformation).      

To experience this point subjectively, listen to the same recording of applause on both a vinyl and a CD.  The CD is limited to producing 22.05 kHz because CDs are sampled at 44.1 kHz.  The vinyl is not limited by a digital sampling rate, so on a properly set up system with speakers capable of generating these higher frequencies, I imagine you may be able to hear a difference - not as pure pitches above 22 kHz but as the impulse response of the applause.       

Another fun experiment would be to listen on a sound system that utilizes Plasma Arc Tweeters (such as the Acapella ION TW 1S)-which can generate frequncies above 50 kHz.  Listen to a jazz record on vinyl or from digital medium with a higher sampling rate (192 kHz, 384 DSD, etc) compared to a CD and see if you can hear the difference in the sizzle of the cymbals depending on the resolution of the recording .  To evaluate whether you can hear this difference requires an appropriate source, sound system, and listening enviornment.   

While I cannot guarantee that you will personally hear the difference, there are people in the world who can and this has been confirmed in blind A/B testing with mastering engineers by company's such as Merging Technologies of Switzerland-the makers of some of the finest recording, mixing, and mastering systems available.  

Thank you again for your comment.  It helps expand a deeper consideration of the phenomena discussed in the article.  

Rotary speakers were common 50 years ago.  Many of the Hammond B-3 organs had an optional leslie speaker system.  Their rotation caused a kind of dynamic vibrato.  Rotating subwoofers?  18 Hz isn't far from our hearing low range.  We feel low frequencies on our skin.  Reproduced acuratly?  Harmonic analysis of a high degree would be needed to check this.  Anybody remember footnotes?  

Hi Mike,

The Thigpen rotary subwoofer mentioned in this article is actually a different design than the Leslie Speakers (which B&H sells along with Hammond Organs).  Please see the link above for more information on how the thigpen rotary subwoofer works.  

It is possible for us to hear below 18 Hz, but it requires a low frequency system capable of generating these frequencies at sufficient SPL levels in order to hear those sounds (something that is very difficult for traditional subwoofer systems to do).  Bruce Thigpen, the subwoofer's inventor shares a very intersting study in the following link which extends the Fletcher Munson curves into the infrasonic territory.  He explains that the threshold for hearing a a 5 Hz wave is 110 dB, which while at 30 Hz would be perceiived to be very loud, is just noticeable at 5 Hz.  Here's the link for more information:


Wow, that's crazy. Let's see some rotary subwoofers.

This is fascinating but I believe we need more about the subwoofers in this article. Which ones (if any) can reproduce this frequency the best? 

I believe they are the same subwoofers which are mounted on NYPD squad cars- look up 'the intimidator'

Hi Jesse -

The Thigpen Rotary Woofer is the world's first true infrasonic home audio or home theater woofer.

Please contact us via e-mail if you have additional questions:  AskBH@BandH.com

Hi Jesse,

The technology mentioned in this article and by Mark S below is in the Thigpen Rotary Subwoofer.  Unlike a traditional subwoofer that uses a moving cone and voice coil assembly, a rotary subwoofer uses a motorized five bladed fan spinning at a constant speed.  The incoming audio signal is translated into pitch changes in the fan blades, with pitch correlating to the amplitude of the pressure wave being formed.  The system actually becomes more efficient as it plays lower, which is the opposite of as traditional subwoofer driver.

This type of subwoofer is expensive and usually reserved for very high end home theaters and sound stages.  For example the fundamental frequency of a helicopter rotor is typically between 10 and 20 Hz, so a sound stage working with helicopter sound effects has a use for rotary subwoofers.  A friend of mine runs a sound stage that employs two of these devices as well as a Helmholtz resonator tuned to 7 Hz for exactly this kind of application.

Alternative applications include creating the sound of Niagara Falls at the Falls' visitor center (as mentioned further in the thread), and testing seismic monitoring systems that detect earthquakes and volcanic eruptions - which is how the University of Hawaii uses the device.  

A detailed explanation of how the technology works is available at Mr. Thigpen's website:




Lots of talk and no show.