level (le´vel)

Any rank, position, or status in a graded scale of values.
acoustic reference l. the biological reference l. for sound measurements. When the term decibel is used to indicate the noise l., a reference quantity is implied; this reference value is usually expressed as a sound pressure of 20 micronewtons per square meter. The reference l. is referred to as 0 decibels, the baseline of the scale of noise l.'s; this baseline is considered the weakest sound that can be heard by a person with very good hearing in an extremely quiet location. Other equivalent reference l.'s still being used include 0.0002 microbar and 0.0002 dyne per square centimeter.
l. of aspiration in clinical psychology, the degree or quality of performance (exhibited in a testing situation) which an individual desires to attain or feels he can achieve.
background l. the concentration (usually low) at which a substance or agent is present or occurs at a particular time and place in the absence of a specific hazard under investigation; an example is the background level of ionizing radiation.
Clark's l. the l. of invasion of primary malignant melanoma of the skin; limited to the epidermis, I; into the underlying papillary dermis, II; to the junction of the papillary and reticular dermis, III; into the reticular dermis, IV; into the subcutaneous fat, V. The prognosis is worse with each successive deeper l. of invasion.
hearing l. the measure of the status of hearing as read directly on the hearing loss scale of an audiometer; described in decibels as a deviation from a standard value for zero on the audiometer.
sound pressure l. (SPL) a measure of sound energy relative to 0.0002 dynes/cm2, expressed in decibels.
window l. the CT number setting in Hounsfield units of the midpoint of the window width, which is the gray scale of the image; a typical window l. for imaging the lungs if -500; for the abdomen, 0.


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