Percussion - research method, which consists in tapping the surface of the body with the assessment of the resulting sound.
Amplitude, frequency and time of attenuation of sound waves depends on the physical properties of the environment in which they arise primarily from the density and mass percutiam body.
The organs and tissues of the human body have different densities, so if percussion they sound different. Bodies, containing air (e.g., light), give a loud, clear bass sound; airless bodies (such as the liver, spleen, heart) - quiet sound stupid. On these properties based topographical percussion, i.e. the definition of the boundaries of the body (for example, the heart can distinguish from the lungs). Knowing, for example, the topographical location of the lungs, by comparative percussion (i.e., percussion in symmetric plots the chest) to detect the dullness of percussion sound associated with consolidation of the lung tissue (pneumonic focus, tuberculosis infiltration, infarction, and others).
By way percussion there are two types: direct and "mediocre". Direct percussion - tapping one or more fingers on the body of the patient. When "mediocre" percussion tapping produce either a finger or a hammer on plessimeter or finger.

Finger finger percussion

Extended finger finger percussion (Fig). When tapped with his finger and thumb use and tactile sensation finger-plessimeter. Percussion impact can be different forces. When comparative percussion, when are caused by fluctuation of a large mass percutiam body, the kick must be strong. Determination of boundaries of the authority (a topographical percussion) the kicker must use the average force. The quietest, or threshold, percussion is used to determine the borders of the absolute dullness of heart and upper limits of the lungs.
Percussion human body distinguish the following types of percussion sound: 1) clear - pulmonary (above the surface of the lungs); 2) stupid - "hip" (over airless bodies, muscles) and 3) of tympanic - "drum" (over the stomach and intestine, containing air). Between the first and second kinds of sounds can be of various transitions.

Percussion (from lat. percussio - tapping). There are two ways P.: direct and indirect. With the direct P. produce the tapping of one or more fingers directly on the body, with mediocre - hammer on tightly attached to the body of plessimeter or finger by finger (G. I. Sokol).
Physical basis of percussion. The sound is caused by the vibrations of matter, derived from the state of rest. If to attack the body, homogeneous, in unit time it gives a constant number of oscillations of the correct form. Such fluctuations are called periodic and sounds that occur at the same time,simple, clear, or tones. When the body is not uniform in composition, it is a separate its parts per unit time doing different is the number of oscillations, and the ear, in addition to the main tone, picks up additional, different in shape oscillations overtones; impurities from their dependent nature, or the tone of the sound. These vibrations are called non-recurrent (deadbeat), and the sound caused by them, - noise. If overtones very high, they give sound with a metal shade.
The sound is also characterized by force (by volume), length and height. The amplitude of oscillations sounding body determines the strength, or the loudness of the sound and depends on the strength of percussion blow, and on the elasticity of the body on which a strike, that is, on its ability to produce oscillating movement. Percussion dense bodies of the oscillation amplitude is smaller, and the sound is quieter. P. less dense bodies, with great firmness, causes fluctuations higher amplitude and much more loud sound. Sound volume determines the mass of a body: the higher it is the sound louder and Vice versa.
The duration of the sound (the time from the moment of occurrence of the sound to its termination) depends on the value of the initial amplitude. Dense body is able to give the initial oscillations of small amplitude; they are quickly turned off, the sound will be shorter. Elastic body, that is less dense, P. give fluctuations of greater amplitude and duration.
The oscillation frequency determines the pitch of the sound. The greater the number of oscillations per unit of time, the higher the pitch, or sound. Dense body, having a lower elasticity, per unit of time do more fluctuations and give a higher tone (the sound)than the less dense and elastic body. Thus, when P. dense bodies arises quiet, short and high sound and percussion elastic, less dense,is a loud, long and low sound.
The human body is not uniform in composition, so when P. various areas of the body can get the sound different force, duration and height. So, percussion chest above the light occurs loud, long and low sound, it is called pulmonary, clear, P. massive organs - liver, spleen, heart, muscles, gives the sound a quiet, short and tall, its called dumb. When P. abdominal wall above the stomach and intestines filled with air, due to resonance percussion enhanced and is reminiscent of the sound that occurs when the drum. This sound is called the tympanic (from the Greek. tympanon - dryer).