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Sound From Ultrasound
Sound from ultrasound is the name given here to the generation of audible sound from modulated ultrasound without using an active receiver. This happens when the modulated ultrasound passes through a nonlinear medium which acts, intentionally or unintentionally, as a demodulator. Parametric array Since the early 1960s, researchers have been experimenting with creating directive low-frequency sound from nonlinear interaction of an aimed beam of ultrasound waves produced by a parametric array using heterodyning. Ultrasound has much shorter wavelengths than audible sound, so that it propagates in a much narrower beam than any normal loudspeaker system using audio frequencies. Most of the work was performed in liquids (for underwater sound use). The first modern device for air acoustic use was created in 1998,105th AES Conv, Preprint 4853, 1998 and is now known by the trademark name "Audio Spotlight", a term first coined in 1983 by the Japanese researchers who abandoned the technol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Modulated Ultrasound
Ultrasound can be modulated to carry an audio signal (like radio signals are modulated). This is often used to carry messages underwater, in underwater diving communicators, and short-range (under five miles) communication with submarines; the received ultrasound signal is decoded into audible sound by a modulated-ultrasound receiver. A modulated ultrasound receiver is a device that receives a modulated ultrasound signal and decodes it for use as sound, navigational-position information, etc. Its function is somewhat like that of a radio receiver. Range limitation Due to the absorption characteristics of seawater, ultrasound (sound at frequencies greater than human hearing, or approximately greater than 20,000 hertz) is not used for long-range underwater communications. The higher the frequency, the faster the sound is absorbed by the seawater, and the more quickly the signal fades. For this reason, most underwater "telephones" either operate in "baseband" mode (at the same fre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
American Technology Corporation
Genasys Inc. is based in San Diego, California. Its long-range acoustic device (LRAD) products are used for long-range acoustic hailing and mass notification. The company was previously named American Technology Corporation (ATC) until 2010 and as LRAD Corporation until 2019. The company's stock trades on the NASDAQ Capital Market with the ticker symbol "GNSS". History Genasys was founded in Utah by Elwood "Woody" Norris as the American Technology Corporation in 1980. From 1988 to early 1992 the company was inactive. Norris recapitalized the company as a Delaware Corporation The Delaware General Corporation Law (Title 8, Chapter 1 of the Delaware Code) is the statute of the Delaware Code that governs corporate law in the U.S. state of Delaware. Adopted in 1899, the statute has since seen Delaware become the most imp ... in 1992. In 1996, the company launched its first directed sound technology and began engineering sound solutions for the commercial, government, and milita ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Directional Sound
Directional Sound refers to the notion of using various devices to create fields of sound which spread less than most (small) traditional loudspeakers. Several techniques are available to accomplish this, and each has its benefits and drawbacks. Ultimately, choosing a directional sound device depends greatly on the environment in which it is deployed as well as the content that will be reproduced. Keeping these factors in mind will yield the best results through any evaluation of directional sound technologies. Systems which guide evacuees during an emergency by the emission of pink noise to the exits are often also called "directional sound" systems. Basic theory In all wave-producing sources, the directivity of any source, at maximum, corresponds to the size of the source compared to the wavelengths it is generating: The larger the source is compared to the wavelength of the sound waves, the more directional beam results . The specific transduction method has no impact o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tinnitus
Tinnitus is the perception of sound when no corresponding external sound is present. Nearly everyone experiences a faint "normal tinnitus" in a completely quiet room; but it is of concern only if it is bothersome, interferes with normal hearing, or is associated with other problems. While often described as a ringing, it may also sound like a clicking, buzzing, hissing or roaring. It may be soft or loud, low- or high- pitched, and may seem to come from one or both ears or from the head itself. In some people, it may interfere with concentration, and in some cases is associated with anxiety and depression. Tinnitus is usually associated with a degree of hearing loss and decreased comprehension of speech in noisy environments. It is common, affecting about 10–15% of people. Most, however, tolerate it well, and it is a significant problem in only 1–2% of all people. It can trigger a fight-or-flight response, as the brain may perceive it as dangerous and important. The word ' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sound Pressure Level
Sound pressure or acoustic pressure is the local pressure deviation from the ambient (average or equilibrium) atmospheric pressure, caused by a sound wave. In air, sound pressure can be measured using a microphone, and in water with a hydrophone. The SI unit of sound pressure is the pascal (Pa). Mathematical definition A sound wave in a transmission medium causes a deviation (sound pressure, a ''dynamic'' pressure) in the local ambient pressure, a ''static'' pressure. Sound pressure, denoted ''p'', is defined by p_\text = p_\text + p, where * ''p''total is the total pressure, * ''p''stat is the static pressure. Sound measurements Sound intensity In a sound wave, the complementary variable to sound pressure is the particle velocity. Together, they determine the sound intensity of the wave. ''Sound intensity'', denoted I and measured in W· m−2 in SI units, is defined by \mathbf I = p \mathbf v, where * ''p'' is the sound pressure, * v is the particle velocity. Acoustic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fourier Transform
A Fourier transform (FT) is a mathematical transform that decomposes functions into frequency components, which are represented by the output of the transform as a function of frequency. Most commonly functions of time or space are transformed, which will output a function depending on temporal frequency or spatial frequency respectively. That process is also called ''analysis''. An example application would be decomposing the waveform of a musical chord into terms of the intensity of its constituent pitches. The term ''Fourier transform'' refers to both the frequency domain representation and the mathematical operation that associates the frequency domain representation to a function of space or time. The Fourier transform of a function is a complex-valued function representing the complex sinusoids that comprise the original function. For each frequency, the magnitude (absolute value) of the complex value represents the amplitude of a constituent complex sinusoid with that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Convolution
In mathematics (in particular, functional analysis), convolution is a operation (mathematics), mathematical operation on two function (mathematics), functions ( and ) that produces a third function (f*g) that expresses how the shape of one is modified by the other. The term ''convolution'' refers to both the result function and to the process of computing it. It is defined as the integral of the product of the two functions after one is reflected about the y-axis and shifted. The choice of which function is reflected and shifted before the integral does not change the integral result (see #Properties, commutativity). The integral is evaluated for all values of shift, producing the convolution function. Some features of convolution are similar to cross-correlation: for real-valued functions, of a continuous or discrete variable, convolution (f*g) differs from cross-correlation (f \star g) only in that either or is reflected about the y-axis in convolution; thus it is a cross-c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DSB-AM
In radio communications, a sideband is a band of frequencies higher than or lower than the carrier frequency, that are the result of the modulation process. The sidebands carry the information transmitted by the radio signal. The sidebands comprise all the spectral components of the modulated signal except the carrier. The signal components above the carrier frequency constitute the upper sideband (USB), and those below the carrier frequency constitute the lower sideband (LSB). All forms of modulation produce sidebands. Sideband creation We can illustrate the creation of sidebands with one trigonometric identity: :\cos(A)\cdot \cos(B) \equiv \tfrac\cos(A+B) + \tfrac\cos(A-B) Adding \cos(A) to both sides: :\cos(A)\cdot +\cos(B)= \tfrac\cos(A+B) + \cos(A) + \tfrac\cos(A-B) Substituting (for instance) A \triangleq 1000\cdot t and B \triangleq 100\cdot t, where t represents time: :\underbrace_\cdot \underbrace_ = \underbrace_ + \underbrace_ + \under ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Total Harmonic Distortion
The total harmonic distortion (THD or THDi) is a measurement of the harmonic distortion present in a signal and is defined as the ratio of the sum of the powers of all harmonic components to the power of the fundamental frequency. Distortion factor, a closely related term, is sometimes used as a synonym. In audio systems, lower distortion means the components in a loudspeaker, amplifier or microphone or other equipment produce a more accurate reproduction of an audio recording. In radio communications, devices with lower THD tend to produce less unintentional interference with other electronic devices. Since harmonic distortion tends to widen the frequency spectrum of the output emissions from a device by adding signals at multiples of the input frequency, devices with high THD are less suitable in applications such as spectrum sharing and spectrum sensing. In power systems, lower THD implies lower peak currents, less heating, lower electromagnetic emissions, and less core loss ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sennheiser Electronic
Sennheiser electronic GmbH & Co. KG (, ) is a German privately held audio company specializing in the design and production of a wide range of high fidelity products, including microphones, headphones, telephone accessories and aviation headsets for personal, professional and business applications. The company's head office is located in Wedemark, near Hanover, and the company is represented in more than 50 countries worldwide. The German company was founded in 1945 by Fritz Sennheiser and it is still an independent family business. Since 2013, Daniel Sennheiser and Andreas Sennheiser have been co-CEOs. They are the third generation of the Sennheiser family to lead the company. According to its own figures, the Sennheiser Group has around 2,801 employees worldwide. In 2019, the total turnover amounted to €756.7 million. History The company was founded in 1945, just a few weeks after the end of World War II by Fritz Sennheiser (1912–2010) and seven fellow engineers of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mitsubishi
The is a group of autonomous Japanese multinational companies in a variety of industries. Founded by Yatarō Iwasaki in 1870, the Mitsubishi Group historically descended from the Mitsubishi zaibatsu, a unified company which existed from 1870 to 1946. The company was disbanded during the occupation of Japan following World War II. The former constituents of the company continue to share the Mitsubishi brand and trademark. Although the group of companies participate in limited business cooperation, most famously through monthly "Friday Conference" executive meetings, they are formally independent and are not under common control. The four main companies in the group are MUFG Bank (the largest bank in Japan), Mitsubishi Corporation (a general trading company), Mitsubishi Electric and Mitsubishi Heavy Industries (both diversified manufacturing companies). History The Mitsubishi company was established as a shipping firm by Iwasaki Yatarō (1834–1885) in 1870 under the name ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LRAD
A long-range acoustic device (LRAD) is an acoustic hailing device (AHD), sound cannon and sonic weapon developed by Genasys. It has been used as a method of crowd control, which has caused permanent hearing damage, having an extremely high decibel capacity (up to 160 dB measured at one meter from the device). Other uses have included for negotiations in siege situations to deal with piracy at sea; for mass notification during natural disasters or other emergencies; and by defense forces, including several navies. History In October 2000 the , an American guided missile destroyer, was bombed in a terrorist attack by al-Qaeda operatives, using a small boat packed with explosives. The naval personnel on Cole were unable to be sure that their messages could be heard by the approaching boat at a sufficient distance to possibly avert the attack. The ship was badly damaged, 17 U.S. Navy sailors killed and 37 injured. Following this attack, navies around the world made s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
