News Column

Patent Issued for Parametric Transducer System and Related Methods

July 16, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- A patent by the inventor Norris, Elwood G. (Poway, CA), filed on February 7, 2013, was published online on July 1, 2014, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.

Patent number 8767979 is assigned to Parametric Sound Corporation (Poway, CA).

The following quote was obtained by the news editors from the background information supplied by the inventors: "The present invention relates generally to the field of parametric loudspeakers and signal processing systems for use in audio production.

"Non-linear transduction, such as a parametric array in air, results from the introduction of sufficiently intense, audio modulated ultrasonic signals into an air column. Self demodulation, or down-conversion, occurs along the air column resulting in the production of an audible acoustic signal. This process occurs because of the known physical principle that when two sound waves with different frequencies are radiated simultaneously in the same medium, a modulated waveform including the sum and difference of the two frequencies is produced by the non-linear (parametric) interaction of the two sound waves. When the two original sound waves are ultrasonic waves and the difference between them is selected to be an audio frequency, an audible sound can be generated by the parametric interaction.

"While the theory of non-linear transduction has been addressed in numerous publications, commercial attempts to capitalize on this intriguing phenomenon have largely failed. Most of the basic concepts integral to such technology, while relatively easy to implement and demonstrate in laboratory conditions, do not lend themselves to applications where relatively high volume outputs are necessary. As the technologies characteristic of the prior art have been applied to commercial or industrial applications requiring high volume levels, distortion of the parametrically produced sound output has resulted in inadequate systems.

"Whether the emitter is a piezoelectric emitter or PVDF film or electrostatic emitter, in order to achieve volume levels of useful magnitude, conventional systems often required that the emitter be driven at intense levels. These intense levels have often been greater than the physical limitations of the emitter device, resulting in high levels of distortion or high rates of emitter failure, or both, without achieving the magnitude required for many commercial applications.

"Efforts to address these problems include such techniques as square rooting the audio signal, utilization of Single Side Band ('SSB') amplitude modulation at low volume levels with a transition to Double Side Band ('DSB') amplitude modulation at higher volumes, recursive error correction techniques, etc. While each of these techniques has proven to have some merit, they have not separately or in combination allowed for the creation of a parametric emitter system with high quality, low distortion and high output volume. The present inventor has found, in fact, that under certain conditions some of the techniques described above actually cause more measured distortion than does a refined system of like components without the presence of these prior art techniques."

In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventor's summary information for this patent: "In accordance with one aspect of the invention, a parametric signal emitting system is provided, including a signal processing system that generates an ultrasonic carrier signal having an audio signal modulated thereon. An amplifier can be operable to amplify the carrier signal having the audio signal modulated thereon. An emitter can be capable of emitting into a fluid medium the carrier signal having the audio signal modulated thereon. A transformer can be operatively coupled between the amplifier and the emitter; wherein a secondary winding of the transformer and the emitter are arranged in a parallel resonant circuit.

"In accordance with another aspect of the invention, a method of optimizing a parametric emitter system having a pot core transformer coupled between an amplifier and an emitter is provided, the method comprising: determining a number of turns required in a primary winding of the transformer to achieve an optimal level of load impedance experienced by the amplifier; determining an optimal physical size of a pot core to contain the transformer, the pot core having an air gap formed in an inner wall thereof with windings of the transformer circumscribing the inner wall; and selecting a physical size of the air gap of the pot core containing the transformer to enable use of a pot core having the determined optimal physical size while avoiding saturation of the transformer during operation of the parametric emitter system.

"In accordance with another aspect of the invention, a method of optimizing performance of an amplifier-emitter pair is provided, including: selecting a pot core to contain and shield a step-up transformer electrically coupled between an amplifier and an emitter, the pot core including an air gap formed in an inner wall thereof; selecting a level of inductance of a secondary winding of the step-up transformer such that electrical resonance can be achieved between the secondary winding and the emitter; and adjusting a size of the air gap of the pot core to decrease an overall physical size of the pot core transformer while avoiding saturation of the transformer during operation of the amplifier-emitter pair.

"In accordance with another aspect of the invention, a method of optimizing a parametric emitter system having a pot core transformer coupled between an amplifier and an emitter is provided, the method including: selecting a number of turns required in a primary winding of the pot core transformer to achieve an optimal level of load impedance experienced by the amplifier; and selecting a number of turns required in a secondary winding of the transformer to achieve electrical resonance between the secondary winding and the emitter.

"Additional features and advantages of the invention will be apparent from the detailed description which follows, taken in conjunction with the accompanying drawings, which together illustrate, by way of example, features of the invention."

URL and more information on this patent, see: Norris, Elwood G.. Parametric Transducer System and Related Methods. U.S. Patent Number 8767979, filed February 7, 2013, and published online on July 1, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8767979.PN.&OS=PN/8767979RS=PN/8767979

Keywords for this news article include: Electronics, Signal Processing, Amplitude Modulation, Parametric Sound Corporation.

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Source: Electronics Newsweekly


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