knackning

Knackning is a Swedish term that denotes tapping or knocking and is used in several contexts to describe a percussive action that helps assess sound properties or mechanical condition. In medicine, knackning refers to percussion, a diagnostic technique in which a clinician taps on a surface of the body to infer the characteristics of underlying tissues and organs.

In clinical examination, percussion is performed by placing a finger (pleximeter) on the patient and tapping with the other hand to generate sounds that travel through the body. The resulting sound and its quality help indicate whether the underlying area is air-filled, solid, or fluid-filled. Common descriptors include resonant for normal lung tissue, hyperresonant in conditions with extra air such as emphysema or pneumothorax, dull over solid organs like the liver or spleen, and tympanic for gas-filled spaces. Percussion aids in locating abnormalities, estimating organ size, and guiding further tests. Limitations include patient effort, obesity, and examiner variability.

Outside medicine, knackning also describes knocking sounds in mechanical systems, notably engine knock or detonation. This abnormal combustion occurs when the air–fuel mixture detonates prematurely or irregularly, which can cause reduced power, increased fuel consumption, and potential engine damage if left unaddressed. Causes include timing problems, low-octane fuel, or deposits in the combustion chamber. Mitigation typically involves adjusting ignition timing, using higher-octane fuel, or reducing engine load.

In other contexts, knackning may refer to deliberate tapping sounds used in acoustic or structural testing, or the general act of knocking on surfaces to assess material properties. The term thus covers a range of perceptible tapping sounds whose character reveals functional or structural characteristics.