Quick Answer. The amount of time it takes for a sound wave to reach the brain is a changing value. The distance of the location from where the sound originates and the type of media the sound travels through are direct factors. Keep Learning.
1 The blood tests most frequently used for liver disease are the aminotransferases (alanine aminotransferase or ALT and aspartate aminotransferase or AST). 2  Normal levels of ALT ranges from about 7-56 units/liter, and 10-40units/liters for AST. Many drugs may cause elevated AST, and ALT and some medications can cause severe damage (for example, acetaminophen [ Tylenol liver damage]). 2  Less common causes of abnormal AST and ALT levels are wide ranging (for example, toxins, and autoimmune diseases).
In order to check for elevated levels your doctor will likely test for increased amounts of two specific liver enzymes: aspartate aminotransferase (AST) and alanine aminotransferase (ALT), whose normal ranges are: 1  AST = 5 to 40 units per liter of serum.  ALT = 7 to 56 units per liter of serum.