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Sound Pressure (sound + pressure)

Distribution by Scientific Domains
Medical Sciences28%

Terms modified by Sound Pressure

  • sound pressure level
    		•

    Selected Abstracts

    Relationship between sound pressure and reaction rate in sonochemical reaction

    THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2009
    Yasuhiko Takuma
    Abstract Relationship between sound pressure in a sonochemical reactor and degradation rate of organic compounds, p -chlorophenol and p -nitrophenol, was investigated. Reaction rates were analyzed as first-order reaction. As a result, linear relationship was shown for each compound. Slope indicating the first reaction rate constant was remarkably affected by the position of the reaction flask. The sound pressure profile was measured and the relationship between the averaged pressure in a flask and the rate constant was shown. The relation was found to be remarkably different between the two. The threshold values were observed as 67kPa for p -chlorophenol and 22kPa for p -nitrophenol, respectively. From these results, it was shown that nature of compounds affects the dependency on sound pressure. On a étudié la relation entre les vitesses de dégradation des composés organiques, le p-chlorophénol et le p-nitrophénol, et la pression acoustique dans une réaction sonochimique. Les premières constantes de vitesse de réaction se sont avérées fortement influencée par la position de la cellule de réaction dans notre installation. Le profil de pression acoustique dans l'installation a été mesuré et la relation entre la pression moyennée dans la cellule et la constante de vitesse a été déterminée. On a trouvé que la relation était significativement différente entre les deux composés et que les valeurs seuils étaient de 100,kPa pour le p-chlorophénol. On a montré également que la nature des composés avait une influence sur leur dépendance à la pression acoustique. [source]

    The structure of vocalization of ewes and male lambs at pasture

    ANIMAL SCIENCE JOURNAL, Issue 1 2009
    Hirofumi NAEKAWA
    ABSTRACT We performed an analysis of the vocalization of 161 ewes and 50 male lambs that were pastured day and night. The vocalization structures of the phonetic notations of the opened-mouth from closed mouth /,aee/ and /,naeee/ and closed-mouth /,,,,/ of ewes, and the opened-mouth from closed-mouth /,eee/ and /,neeee/ and closed-mouth /,,,,/ of male lambs were studied in terms of their audio characteristics. The items subject to analysis included duration of each vocalization, fundamental frequency, sound pressure and first formant (F1), second formant (F2), and third formant (F3). Among the male lambs, the duration of each call type showed significant differences depending on the behavior types or the target types, and the closed-mouth to open-mouth sounds, /,eee/ and /,neeee/ showed a tendency to be longer than the closed-mouth sound of /,,,,/. A significant correlation (r = 0.9, P < 0.05) was observed between the fundamental frequency and F1 with the /,eee/ type of call of the male lambs when the vocalization was targeted toward the stockperson. When the ewes' behavior pattern was grazing and moving and the calling target was an ewe, the sound pressure significantly differed between /,,,,/ and /,naeee/ (P < 0.05). From the analysis of the call durations, the fundamental frequencies, the sound pressures and formants, and the particular characteristics in sound structure were shown to vary according to the vocalization conditions and the situations, and where the animals were placed, even within the same call types. [source]

    Technical characterization of an ultrasound source for noninvasive thermoablation by high-intensity focused ultrasound

    BJU INTERNATIONAL, Issue 3 2002
    K.U. Köhrmann
    Objective,To develop a generator for high-intensity focused ultrasound (HIFU, a method of delivering ultrasonic energy with resultant heat and tissue destruction to a tight focus at a selected depth within the body), designed for extracorporeal coupling to allow various parenchymal organs to be treated. Material and methods,The ultrasound generated by a cylindrical piezo-ceramic element is focused at a depth of 10 cm using a parabolic reflector with a diameter of 10 cm. A diagnostic B-mode ultrasonographic transducer is integrated into the source to allow the focus to be located in the target area. The field distribution of the sound pressure was measured in degassed water using a needle hydrophone. An ultrasound-force balance was used to determine the acoustic power. These measurements allowed the spatially averaged sound intensity to be calculated. The morphology and extent of tissue necrosis induced by HIFU was examined on an ex-vivo kidney model. Results,The two-dimensional field distribution resulted in an approximately ellipsoidal focus of 32×4 mm (, 6 dB). The spatially maximum averaged sound intensity was 8591 W/cm2 at an electrical power of 400 W. The lesion caused to the ex-vivo kidney at this maximum generator power with a pulse duration of 2 s was a clearly delineated ellipsoidal coagulation necrosis up to 8.8×2.3 mm (length×width) and with central liquefied necrosis of 7.9×1.9 mm. Conclusion,This newly developed ultrasound generator with a focal length of 10 cm can induce clear necrosis in parenchymal tissue. Because of its specific configuration and the available power range of the ultrasound generator, there is potential for therapeutic noninvasive ablation of tissue deep within a patient's body. [source]

    The acoustic hood: a patient-independent device improving acoustic noise protection during neonatal magnetic resonance imaging

    ACTA PAEDIATRICA, Issue 8 2009
    Anders Nordell
    Abstract Background:, Magnetic resonance imaging (MRI) is today the imaging modality of choice to investigate the neonatal brain. However, the acoustic noise during scanning is very loud, often exceeding 100 dBA. Aim:, To reduce the acoustic noise during MRI for neonatal patients. If effective, this would create a safer environment and also result in fewer aborted examinations due to poor image quality from patient motion. Methods:, A passive acoustic noise protector, the acoustic hood, was built out of dampening material. Sound pressure measurements with and without the acoustic hood were performed using our clinical neonatal scan protocol, consisting of eight imaging sequences. The acoustic hood is placed over the newborn inside the MR scanner tunnel during the examination to absorb acoustic noise. Results:, The acoustic noise level was substantially reduced using the acoustic hood. Peak sound pressure was reduced 16.18,22.21 dBA depending on the pulse sequence. For the entire frequency spectra, reduction were between 4,13.59 dBA again varying with the pulse sequence. Conclusion:, Acoustic noise can be reduced further than before by using the patient-independent acoustic hood in addition to other noise protection. We recommend the use of three passive hearing protections during neonatal MRI: (1) dental putty, (2) paediatric ear muffs, and (3) the acoustic hood. [source]

    From Universal Laws of Cognition to Specific Cognitive Models

    COGNITIVE SCIENCE - A MULTIDISCIPLINARY JOURNAL, Issue 1 2008
    Nick Chater
    Abstract The remarkable successes of the physical sciences have been built on highly general quantitative laws, which serve as the basis for understanding an enormous variety of specific physical systems. How far is it possible to construct universal principles in the cognitive sciences, in terms of which specific aspects of perception, memory, or decision making might be modelled? Following Shepard (e.g., 1987), it is argued that some universal principles may be attainable in cognitive science. Here, 2 examples are proposed: the simplicity principle (which states that the cognitive system prefers patterns that provide simpler explanations of available data); and the scale-invariance principle, which states that many cognitive phenomena are independent of the scale of relevant underlying physical variables, such as time, space, luminance, or sound pressure. This article illustrates how principles may be combined to explain specific cognitive processes by using these principles to derive SIMPLE, a formal model of memory for serial order (Brown, Neath, & Chater, 2007), and briefly mentions some extensions to models of identification and categorization. This article also considers the scope and limitations of universal laws in cognitive science. [source]

    The structure of vocalization of ewes and male lambs at pasture

    ANIMAL SCIENCE JOURNAL, Issue 1 2009
    Hirofumi NAEKAWA
    ABSTRACT We performed an analysis of the vocalization of 161 ewes and 50 male lambs that were pastured day and night. The vocalization structures of the phonetic notations of the opened-mouth from closed mouth /,aee/ and /,naeee/ and closed-mouth /,,,,/ of ewes, and the opened-mouth from closed-mouth /,eee/ and /,neeee/ and closed-mouth /,,,,/ of male lambs were studied in terms of their audio characteristics. The items subject to analysis included duration of each vocalization, fundamental frequency, sound pressure and first formant (F1), second formant (F2), and third formant (F3). Among the male lambs, the duration of each call type showed significant differences depending on the behavior types or the target types, and the closed-mouth to open-mouth sounds, /,eee/ and /,neeee/ showed a tendency to be longer than the closed-mouth sound of /,,,,/. A significant correlation (r = 0.9, P < 0.05) was observed between the fundamental frequency and F1 with the /,eee/ type of call of the male lambs when the vocalization was targeted toward the stockperson. When the ewes' behavior pattern was grazing and moving and the calling target was an ewe, the sound pressure significantly differed between /,,,,/ and /,naeee/ (P < 0.05). From the analysis of the call durations, the fundamental frequencies, the sound pressures and formants, and the particular characteristics in sound structure were shown to vary according to the vocalization conditions and the situations, and where the animals were placed, even within the same call types. [source]