Basic and Technical Aspects of Ultrasound
Arianna D'Angelo, Nazar N. Amso in Ultrasound in Assisted Reproduction and Early Pregnancy, 2020
The speed of sound depends on the medium through which it is propagating. It is generally affected by two main things, namely, density and compressibility. Sound generally travels faster in solids and liquids than in gas. The speed of sound is faster in materials that have some rigidity and slower in softer materials. Knowing the speed of ultrasound in various tissues is important because: It gives the ability to convert echo return time into depthThe velocity can be used to calculate the acoustic impedanceRefraction occursVelocity must be known to calculate Doppler shift
Cardiovascular Imaging for Early Detection of Coronary Artery Disease
Ayman El-Baz, Jasjit S. Suri in Cardiovascular Imaging and Image Analysis, 2018
Echocardiography (ultrasonography of the heart) is an imaging modality that utilizes ultrasound-frequency (>20 kHz) waves to generate images of the heart and great vessels. Echocardiography is the primary bedside imaging modality used for the evaluation of the cardiovascular (CV) system and has a well-established role as an inexpensive, first-line method of early CV disease (CVD) assessment. Soundwaves are produced via a transducer and are emitted inside the body of the patient being examined; these initial waves are called incident waves. As incident waves travel through body tissues, they react differently with each one. Generally, waves of sound behave similarly to those of electromagnetic waves (light). As occurs with electromagnetic waves, the wavelength of soundwaves is inversely proportional to its frequency and is determined based on the formula where λ is the wavelength, ν is the velocity of the wave in the medium it is traversing, and f is the frequency of the wave. As a result, waves with higher frequencies (e.g., ultrasound frequencies) have smaller wavelengths. These smaller wavelengths make ultrasound waves capable of being reflected by much smaller objects than waves of lower frequencies, which affords ultrasonography a good special resolution.
Energy Sources in Urology
Anthony R. Mundy, John M. Fitzpatrick, David E. Neal, Nicholas J. R. George in The Scientific Basis of Urology, 2010
Waves carry vibrations through a medium (solid, liquid, gas) and are created whenever an object moves within a fluid (either gas or liquid). Waves have a measurable speed, wavelength, and frequency and are created when an object moves, compressing molecules adjacent to it. This compression is in turn transmitted to further adjacent molecules and so on. The compression is therefore relieved in the original region but is propagated onward to a new region with the formation of a wave. The speed of this wave is dependant on the characteristics and temperature of the medium within which it travels (solids > liquids > gases). It is independent of pressure, frequency, and amplitude. Acoustic waves differ from electromagnetic waves in that individual molecules do not travel with acoustic waves. Electromagnetic energy displays wave-particle duality with particles (photons) physically traveling through space. Acoustic energy therefore requires a medium where as electromagnetic energy does not: light can travel through a vacuum but sound cannot.
The Lombard effect associated with Chinese male alaryngeal speech
Published in International Journal of Speech-Language Pathology, 2019
Manwa L. Ng, Gloria C. K. Tsang
ES and TE speakers, however, seemed to be using a different strategy to increase vocal intensity than EL speakers. According to speech acoustics, sound is generated when the sound source is set into vibration. Its rate of vibration corresponds to the pitch (fundamental frequency), and the excursion of vibration determines the loudness (intensity). In the case of vocal fold vibration, the faster the vocal folds vibrate, the higher is the pitch; and the greater excursion of the vocal folds and the more forceful the vocal folds meet, the louder is the sound. This is achieved by increasing the medial compression of vocal fold adduction, combined with a greater subglottal pressure. Apparently, they are results of subtle and fine coordination of intrinsic and extrinsic laryngeal musculatures, combined with appropriate respiratory activity. According to Zemlin (1987), to increase vocal loudness, greater medial compression of vocal folds yielding a greater glottal resistance, and thus increased subglottal pressure are evidenced. Analogously, ES and TE speakers might increase their output intensity by controlling the adductory force of their PE segment, while increasing the sub-neoglottal pressure. For TE speakers, this can be done by increasing the pulmonary pressure. For ES speakers, this could be done by increasing the intraesophageal pressure. Obviously, this speculative explanation needs further evidence. Direct and indirect measurements such as oesophageal manometric data and perhaps electromyographic (EMG) data are needed to confirm the above conjecture.
Stress measurement using speech: Recent advancements, validation issues, and ethical and privacy considerations
Published in Stress, 2019
George M. Slavich, Sara Taylor, Rosalind W. Picard
These limitations of self-report, interview-, and biomarker-based approaches make assessing stress using speech very attractive, especially given that doing so is now relatively inexpensive and non-intrusive. When preparing to speak, an individual must decide which sequence of words will best communicate his or her intended message. Stress can affect these decisions and change the wording, grammar, and timing of speech, which can, in turn, be used as vocal markers of stress (Paulmann, Furnes, Bøkenes, & Cozzolino, 2016; Scherer & Moors, 2019). However, stress induces other changes as well. In order to produce speech, for example, the body modulates the tension of numerous muscles in order to force air through the vocal folds and out the vocal tract to produce sound waves (Titze, 2000). Stress increases both muscle tension and respiration rate, which in turn change the mechanics of speech production and, consequently, the way that speech sounds (Sondhi, Khan, Vijay, & Salhan, 2015; Zhou, Hansen, & Kaiser, 2001).
Enzymes and their turnover numbers
Published in Expert Review of Proteomics, 2019
Gary B. Smejkal, Srikanth Kakumanu
Other examples of the speed at which enzymes mediate biochemical reactions include DNA and protein synthesis. DNA synthesis occurs at a rate of 50 nucleotides per second in eukaryotes and nearly 1,000 nucleotides per second in some bacteria [9]. Human normoblasts, which comprise less than 0.2% of the total cell mass in the human body, collectively replicate about 4 kilometers of DNA every second [10]. This is nearly 12 times faster than the speed of sound, which travels 0.34 kilometers per second in air. This rate of DNA synthesis, if extrapolated for the entire human population in terms of total DNA length, would be able to trace the orbit of Pluto in just 1.3 seconds [10]. To put in perspective, Pluto has an orbital period of 247 years and it has completed only one-third its orbit around the sun since its discovery in 1930.
Related Knowledge Centers
- Environmental Noise
- Physiology
- Ultrasound
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- Psychology
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- Acoustical Engineering
- Bioacoustics
- Noise Control
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