Every aspect of electronic reproduction of sound has enjoyed significant technological advances during the past 50 years with one exception -- the loudspeaker. Consumer playback equipment has evolved from the mechanical phonograph record to the cassette tape to CD and now DVD. Recording devices first used wire, then magnetic tape, and now use digital audio tape, computer hard disks, and memory chips. Electronics migrated from tubes to transistors to the digital technology of today. Improvements have eliminated wow & flutter, turntable rumble, L/R crosstalk, and a host of other undesirable artifacts. Noise and distortion have been reduced to imperceptible levels.
Basic loudspeaker operating principles, however, have remained unchanged for more than 70 years. Since 1925, when C.W. Rice and E.W. Kellogg described basic, direct-radiating speaker parameters, there have been few, if any, fundamental changes in speaker design or in the way in which electrical impulses are converted into sound. Despite its long life and the efforts made to improve it, the familiar, wide-range high-fidelity loudspeaker typically is less than one percent efficient, and its reproduction quality is largely dependent upon the size and kind of enclosure, with smaller versions generally producing inferior sound.
What if a technology could be developed that would eliminate many of the undesirable artifacts of loudspeaker systems. Think about an audio reproduction system that could produce the broad range of frequencies required for human hearing with no direct radiating transducer devices, no crossovers, no cone or cabinet resonances, and reduced weight, size, cost, and room interaction.
HyperSonic Sound IS:
HyperSonic Sound is NOT:
These days it is highly unusual to find something that is truly original. The terms "quantum leap" and "paradigm shift" are so overused that, when one runs across a technology that is truly worthy of such a description, few believe it.
Fortunately, like all extraordinary developments, this elegant technology can be described with an economy of words.
The Norris Acoustical Heterodyne technology projects silent ultrasonic energy which the inventor, Elwood "Woody" Norris, refers to as "HyperSonic Sound" (HSS™) that is converted to audible energy in the column of ultrasound. The sound is actually created in mid-air. This is not an illusion. The audible sound wave is created by air molecules as they are displaced by the ultrasonic waves.
The audible sound is produced without the conventional speakers excess baggagethere are no voice coils, cones, crossover networks, or enclosures.
A Brief Look at Loudspeakers
About a half-dozen commonly used speaker types are in general use today. They range from piezoelectric tweeters that attempt to recreate the high end of the audio spectrum, to mid-range speakers to woofers that produce the lower frequencies. It is virtually impossible to produce the 10 octave audible range with a single driver.
Whether they be electro-magnetic, electrostatic, or some other design, all loudspeakers today have one thing in common: they are direct radiatingthey are fundamentally a piston-like device designed to directly pump air molecules into motion to create the audible sound waves we hear. HSS technology causes the air to make sound.
As electronics have advanced and speaker technology has been pushed to its limits, a whole array of terms have come to define the various forms of conventional speaker distortion: amplitude distortion, harmonic distortion, intermodulation distortion, phase distortion, crossover distortion, cone resonance, and so forth.
Every form of distortion contributed by a loudspeaker is traceable to some aspect of its mechanical nature: mass, magnetic structure, enclosure design, cone construction, etc. All form an important part of the final products capability to perform its function in as perfect a manner as possible.
Speaker cone motion is subject to the laws of physics. This all-important element, more than any other in a speaker system, affects the overall purity of sound and can be a source of various forms of distortion. Ideally, when reproducing sound, the speaker cone should follow precisely the delicate nuances of any electrical waveform presented to it. The cone or radiating surface of a perfect loudspeaker would have virtually no mass nor resonances over the entire range of hearing.
HyperSonic Sound technology does precisely thatit utilizes the air molecules present, which have very little mass and no resonance. The faithful reproduction of sound is freed from bulky enclosures. There are no magnets, crossovers, woofers, tweeters, or bulky enclosures.
Fundamentally, HSS works by emitting a beam of ultrasonic energy which is converted to an audible wave in mid-air. An important by-product of the technique is that sound may be directed to just about any desired point in the listening environment. This provides outstanding flexibility, while allowing an unprecedented manipulation of the sounds source point.
It helps to visualize the traditional loudspeaker as a bare light bulb, and HSS technology as a flashlight.
As with the light bulb, a traditional loudspeaker radiates sound in all directions. A listener can stand anywhere in an acoustical environment and point to the speaker as the source of the sound.
HSS technology is much more analogous to the beam of light from a flashlight. If you stand to the side or behind the light, you can only see the light when it strikes a surface. HSS technology is similar in that you can direct the ultrasonic emitter toward a hard surface, a wall for example, and the listener perceives the sound as coming from the spot on the wall. The listener does not perceive the sound as emanating from the face of the transducer, only from the reflection off the wall.
However, look directly into the lens of a flashlight and you will see the highest intensity of light and it will appear to emanate from the face of the flashlight. If you direct an HSS ultrasonic emitter directly towards a listener, the listener will perceive the sound as emanating from the direction of the emitter. In fact, the sonic sound waves are being created all along the ultrasonic wave in front of the emitter. A by-product of this ability to "beam" the sound is to tightly control the dispersion and project the sound much further distances than conventional loudspeakers.
Dispersion of the audio wavefront can be tightly controlled by contouring the face of the HSS ultrasonic emitter. For example, a very narrow wavefront might be developed for use on the face of a computer screen while a home theater system might require a wider wavefront to envelope multiple listeners.
Non-Linearity of Air
When two sound sources with differing frequencies are positioned relatively closely together and are of a sufficiently high amplitude, new tones appear: one lower in frequency than either of the two original ones and several which are higher in frequency than the original two.
There are now multiple tones where before there were only two. It can be demonstrated mathematically that the new tones correspond to integer multiples of each fundamental, as well as the sum and the difference of the two original ones, which we refer to as combination tones.
For example, if you were to emit 200,000 Hz and 201,000 Hz into the air, with sufficient energy to produce a sum and difference tone, you would produce the sum - 401,000 Hz - and the difference - 1,000 Hz, which is in the range of human hearing.
The HSS concept originates from this theory of combination tones, a phenomenon known in music for the past 200 years as "Tartini tones." It was long believed that Tartini Tones were a form of beats because their frequency equals the calculated beat frequency.
However, it was Hermann von Helmholtz (1821-1894) who completely re-ordered the thinking on these tones. By reporting that he could also hear summation tones (whose frequency was the sum rather than the difference of the two fundamental tones), Helmholtz demonstrated that the phenomenon had to result from a non-linearity. Could a method be found today to utilize this non-linearity of air molecules in a manner similar to the non-linearity of an electronic mixer circuit?
In theory, the principle appears quite simple. Yet, until now, no one has succeeded in practical implementation.
Although air is far from being a non-linear electrical circuit, air molecules behave non-linearly (which allows mixing) as the amplitude increases. This is why, mathematically, HSS technology is generally similar to heterodyning in electronics. In a radio receiver, two electrical signals are mixed in such a way as to produce sum and difference frequencies. Virtually every receiver in the world, whether radio, TV, or cellular phone, uses this technique. Thus, the HSS system can be considered as a form of heterodyningacoustical heterodyningin that the creation of difference frequencies from other higher frequency waves also takes place.
In air, the effect works in such a way that if ultrasonic signals are increased in amplitude, a difference frequency is created.
Range of Hearing
Compared to the human ear, even todays highest technology loudspeaker is a very inadequate device. The human ear is sensitive to frequencies from about 20 Hz to 20,000 Hz (the "audio" range), and can detect vibration amplitudes that are comparable in size to a hydrogen atom.
If the range of human hearing is considered as a percentage of the progression from the lowest audible frequency to the highest, it represents a shift of 100,000%. No single loudspeaker can operate efficiently or uniformly over this range of frequencies. We must split the audio spectrum into smaller sections. This requires multiple transducers and crossovers to create a high-fidelity system with current technology.
If the range of frequencies we can hear could be mixed with a much higher frequency "carrier" such as 200 kHz, the required frequency shift for a single transducer would be only 10%. Building a transducer that only has to produce audio uniformly over a 10% frequency shift would be simpler. For example, if a loudspeaker only needed to operate from 1000 to 1100 Hz (10%), an almost perfect transducer could be designed.
If the audio spectrum could be superimposed on this high frequency carrier and emitted into the air as an ultrasonic acoustical wave, the only thing remaining would be to "down covert" the ultrasonic energy to sonic energy we could hear.
How HSS Works
HyperSonic Sound technology utilizes proprietary custom-designed, ultrasonic emitters, that are capable of operating over a frequency range of at least 10%; therefore, if the carrier frequency were 200,000 Hz, a 20,000-Hz upward swing from that point would create the entire audible range of hearing. Several ultrasonic emitter designs are proprietary* to ATC. Other emitter types will be made available by ATC as future applications require. Each of these various emitters will be small and thin in comparison to existing speakers.
This specially constructed ultrasonic emitter produces a "HyperSonic" energy wave, custom-generated by proprietary* electronics, with the proper characteristics to cause the difference frequencies to become audible. The high level of energy in the ultrasonic wave actually causes air molecules within the ultrasonic wave column to vibrate at the difference frequencies, causing a sonic (audible) wavefront to be produced all along the ultrasonic column.
* Patent Pending
Ultrasonic Emitter Devices
Not only has the conventional speakers crossover network and enclosure been eliminated, but an HSS radiating ultrasonic emitter is so small and light weight that the inertial considerations ordinarily associated with traditional direct-radiation speakers are virtually non-existent. (And so is just about everything else associated with the conventional speaker: the voice coil and support structure normally used to attach the moving cone in place.)
Small & Light Weight
No Magnets or Voice Coils
Easy to Mount, Very Thin
No Cabinets, Boxes or Housings
No Mechanical Vibration
Using HSS Technology, designers can control the vertical and horizontal size of the ultrasonic energy column. Sound can be "focused" directly at the listening audience, reducing the reflections and destructive interference from the surrounding walls, floor, and ceiling. For the first time in history, we can largely ignore the negative effects of room acoustics on sound reproduction.
Traditional loudspeakers convert electrical energy into acoustical energy at an efficiency of approximately 0.25% - 0.50%. Electrostatic speakers operate at approximately 3% efficiency. A large portion of this inefficiency is caused by the mismatch of the acoustical impedance of air with the impedance of the loudspeaker cone material. Air has an acoustical impedance of .0004 MegaRayls (named after the British physicist Lord Rayleigh). The typical loudspeaker has between 1.5 and 2.0 MegaRayls of acoustical impedance. The acoustical impedance of the HSS ultrasonic emitter is much closer to that of air. Improved system efficiency will come from superior air coupling of the emitter, the ability to focus sound in a specific direction.
The ability to produce the entire audible spectrum of frequencies from a single source has been the goal of transducer engineers for the past 50 years. The improvement in phase response, time alignment, and frequency response is obvious.
What About Performance?
Preliminary testing of ATC proof-of-concept prototypes shows that HSS technology has the potential for the following performance specifications:
What about our animal friends?
In reality, sound waves have a relatively small energy content. For instance, if every man, woman, and child in New York City spoke at the same time, the total acoustical power present would barely brew a single cup of coffee.
The most familiar applications for ultrasonics today are in the medical field, and do not generally involve radiating into the air. More commonly, ultrasound is used to image the brain and other organs. The most familiar application of ultrasonic waves is the sonogram, an imaging device used regularly in the prenatal treatment of pregnant women to monitor fetal development. Interestingly, it was Elwood Norris who, years ago, developed one of the core technologies that later evolved into the sonogram.
Abundant data in medical literature validates the fact that medical ultrasound at these frequencies is harmless. There is no need to worry about pets, either. Dogs and cats can hear sounds up to perhaps 40,000 Hz, and HSS will operate well above this range.
Applications for HSS
HSS technology applications are limited only by the imagination. High volume applications are numerous and include:
Besides consumer electronics, the entertainment industry is expected to be fundamentally influenced by this development. In a movie theater, sound can be made to emanate directly from an actors mouth on the screen. Special effects will no longer be limited to the capability of loudspeakers positioned around the auditorium.
Until now, it has been difficult for a hearing aidregardless of priceto reproduce the entire audio spectrum. This no longer need be the case. With HSS, hearing aids may also shrink further in size.
Virtual reality, in large-scale applications, has been brought another step closer.
No longer is the quality of the sound related to the type of a speakers enclosure. Everywhere and anywhere a speaker is in use todayships, aircraft, hospitals, automobilesHSS technology can replace bulkier, inefficient speakers, and provide far better accoustical results than we have ever heard.
Truly, this is a quantum leap, a paradigm shift.
American Technology Corporation has established a strong portfolio of pending patents covering every aspect of HSS technology and intends to license HSS on a non-exclusive basis to manufacturers of products requiring the reproduction of sound. ATC will provide a commercial source for HSS Ultrasonic Emitters and the DSP Pre-Processing required to develop the proprietary HSS ultrasonic wave along with the superimposed audio.
Another byproduct of HSS technology is the high impedance of the ultrasonic emitters. Power amplifier stages can be engineered without the requirement to produce high current, making them lower cost, lighter-weight, and less bulky.
Potential implementation for monaural applications:
Potential implementation for stereo applications:
Potential implementation for computers:
Potential implementation for home theater applications: