Tinnitus masker issues associated with use of tinnitus maskers: the "safe" level of continuous sound depends on the duration of the sound. For maskers worn continuously, or most of the day, a safe level is no more than 70db, in accordance with EPA maximum safe exposure level for 24-hour environmental sound. Maskers louder than 45db or so (the ambient background level of an average home living area) may start to interfere with understanding conversation (about 60db). Masking of high frequency tinnitus (>6,000hz) is difficult because of the resonance characteristics of the human ear as well as high frequency limitations of in-ear devices.
Supernumerary body part two or more different populations of genetically distinct cells that originated in different zygotes that have merged; anatomical structures are typically mixed depending on which cells are prevalent in different body parts, for example plants can have two different types of flowers. A mosaic is a genetic anomaly similar in nature and effects to a chimera: genetically different populations of cells within one organism, originated from some propagated mutation of a single cell rather than from outside sources. In Hindu mythology, additional limbs and heads are considered a sign of power. In Greek mythology, Artemis, the goddess of fertility, was