Noise is frequently described as 'unwanted sound'. Within this context, environmental noise is generally present in some form in all areas of human, animal, or environmental activity. The effects in humans of exposure to environmental noise may vary from emotional to physiological and psychological. Noise at low levels is not necessarily harmful. Environmental noise can also convey a sense of liveliness in an area, which can be desirable. However, the adverse effects of noise exposure (i.e. noise pollution) could include: interference with speech or other 'desired' sounds, annoyance, sleep disturbance, anxiety, hearing damage and stress-related cardiovascular health problems.