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

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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.      

Discussion 17

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What.....?

Agree,

Lots of talk and no show.

WHAT????

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'

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

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?  

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.

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.

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. 

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

Nice tiger photo.

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....

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?

      .peter.

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.