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The first heart sound, or S 1, forms the "lub" of "lub-dub" and is composed of components M 1 (mitral valve closure) and T 1 (tricuspid valve closure). Normally M 1 precedes T 1 slightly. It is caused by the closure of the atrioventricular valves , i.e. tricuspid and mitral (bicuspid), at the beginning of ventricular contraction, or systole .
The letters s, t, n, l are frequently called 'alveolar', and the language examples below are all alveolar sounds. (The Extended IPA diacritic was devised for speech pathology and is frequently used to mean "alveolarized", as in the labioalveolar sounds [p͇, b͇, m͇, f͇, v͇], where the lower lip contacts the alveolar ridge.)
A less common periodic sound source is the vibration of an oral articulator like the tongue found in alveolar trills. Aperiodic sound sources are the turbulent noise of fricative consonants and the short-noise burst of plosive releases produced in the oral cavity.
In a healthy heart, there are only two audible heart sounds, called S1 and S2. The first heart sound S1, is the sound created by the closing of the atrioventricular valves during ventricular contraction and is normally described as "lub". The second heart sound, S2, is the sound of the semilunar valves closing during ventricular diastole and is ...
The third form of initiation in human language is lingual or velaric initiation, where a sound is produced by a closure at two places of articulation, and the airstream is formed by movement of the body of the tongue. Lingual stops are more commonly known as clicks, and are almost universally ingressive.
How sounds make their way from the source to the brain. Audition, the process of hearing sounds, is the first stage of perceiving speech. Articulators cause systematic changes in air pressure which travel as sound waves to the listener's ear. The sound waves then hit the listener's ear drum causing it to vibrate.
For instance, in some sounds in many languages, the surface of the tongue contacts a relatively large area from the back of the upper teeth to the alveolar ridge, which is common enough to have received its own name, denti-alveolar. Likewise, the alveolar and post-alveolar regions merge into each other, as do the hard and soft palate, the soft ...
The three types of ingressive sounds are lingual ingressive or velaric ingressive (from the tongue and the velum), glottalic ingressive (from the glottis), and pulmonic ingressive (from the lungs). The opposite of an ingressive sound is an egressive sound , by which the air stream is created by pushing air out through the mouth or nose.