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A sound attenuator, or duct silencer, sound trap, or muffler, is a noise control acoustical treatment of Heating Ventilating and Air-Conditioning (HVAC) ductwork designed to reduce transmission of noise through the ductwork, either from equipment into occupied spaces in a building, or between occupied spaces.
The head rests on the top part of the vertebral column, with the skull joining at C1 (the first cervical vertebra known as the atlas). The skeletal section of the head and neck forms the top part of the axial skeleton and is made up of the skull, hyoid bone, auditory ossicles, and cervical spine. The skull can be further subdivided into:
The shoulder joint is considered a ball-and-socket joint. However, in bony terms the 'socket' (the glenoid fossa of the scapula) is quite shallow and small, covering at most only a third of the 'ball' (the head of the humerus). The socket is deepened by the glenoid labrum, stabilizing the shoulder joint. [1] [2]
The glenoid fossa of the scapula or the glenoid cavity is a bone part of the shoulder.The word glenoid is pronounced / ˈ ɡ l iː n ɔɪ d / or / ˈ ɡ l ɛ n ɔɪ d / (both are common) and is from Greek: gléne, "socket", reflecting the shoulder joint's ball-and-socket form. [1]
In human anatomy, the glenohumeral ligaments (GHL) are three ligaments on the anterior side of the glenohumeral joint (i.e. between the glenoid cavity of the scapula and the head of the humerus; colloquially called the shoulder joint).
The capsule of the glenohumeral (shoulder) joint is the articular capsule of the shoulder.It completely surrounds the joint. It is attached above to the circumference of the glenoid cavity beyond the glenoidal labrum, and below to the anatomical neck of the humerus, approaching nearer to the articular cartilage above than in the rest of its extent.
The obstruction caused by the head can account for attenuation (reduced amplitude) of overall intensity as well as cause a filtering effect. The filtering effects of head shadowing are an essential element of sound localisation —the brain weighs the relative amplitude, timbre , and phase of a sound heard by the two ears and uses the ...
Acoustic attenuation in water is frequency-squared dependent, namely =. Acoustic attenuation in many metals and crystalline materials is frequency-independent, namely =. [10] In contrast, it is widely noted that the of viscoelastic materials is between 0 and 2.