dimanche 4 février 2007, par Yannick
L’Ohm (symbole Ω) est l’unité dérivée de résistance électrique du système international (SI). Il a été nommé en honneur de Georg Ohm.
Définition : Résistance électrique entre deux points d’un conducteur lorsqu’une différence de potentiel constante de 1 volt, appliquée entre ces deux points, produit dans ce conducteur un courant de 1 ampère le dit conducteur n’étant le siège d’aucune force électromotrice.
Om̐ ou Aum est une syllabe sacrée sanskrite se rencontrant dans plusieurs religions : l’hindouisme, le bouddhisme, le jaïnisme, le sikhisme, le brahmanisme ou la religion sanskrit. On la nomme aussi udgitha ou pranava mantra (« mantra primordial », le mot prana signifiant également « vibration vitale »).
La prononciation de om̐ est censée se faire d’une manière spécifique : a émerge du fond de la gorge, vers le palais, u roule sur la langue et m termine sur les lèvres. A symbolise l’éveil, u, le rêve, m, le sommeil. Cette syllabe est considérée comme le son originel, primordial. Elle serait la somme et la substance de tous les mots qui puissent émaner de la gorge de l’homme. C’est aussi un symbole de l’univers absolu.
Aum Iti Ek Akshara Brahman : Aum, cette unique syllabe est le brahmanisme. La quasi-totalité des mantras bouddistes commencent par Om̐, à tel point qu’il est devenu un symbole du bouddhisme.
A Hum is a sound made by singing a wordless tone with the mouth completely closed, forcing the sound to emerge from the nose. To hum is to produce such a sound, most often with a melody. This necessarily keeps the volume at a low level, so humming is rarely used in musical productions, with some exceptions such as scat singing and vocables. Humming is sometimes used to keep the melody when the singer does not know the lyrics.
A hum has a particular timbre (or sound quality), usually a monotone or with slightly varying tones. There are other similar sounds not produced by human singing that are also called hums, such as a sound produced by machinery in operation or by an insect in flight. The hummingbird was named for the sound that bird makes in flight.
The Hum is a generic name for a series of phenomena involving a persistent and invasive low-frequency humming noise not audible to all people. Hums have been reported in various geographical locations. In some cases a source has been located. A well known case was reported in Taos, New Mexico, and thus The Hum is sometimes called the Taos Hum : the unsolved nature of the hum in Taos has become part of the appeal of Taos. Hums have been reported all over the world, especially in Europe. The Hum is most often described as sounding somewhat like a distant idling diesel engine. Typically "The Hum" is difficult to detect with microphones, and its source and nature is a mystery to the listener.
Electric hum, mains hum, or power line hum is an audible oscillation at the frequency of the mains alternating current, which is usually 50 or 60 hertz depending on the local electric utility configuration (see Mains electricity). The sound often has heavy harmonic content.