·      Where there are exceptionally low background ambient noise levels.

·      A noticeable fluctuation in sound level which would call attention to the source.

·      Pure tones or discrete frequency sounds regardless of the overall intensity.

·      Any noises that disturb or interfere with sleep, communication or recreation.

·      Intermittent, impulsive or startling noises.

·      Low frequency sound which causes vibrations in windows, walls and other parts of building structures.

·      Distracting noise sources, such as breaking of glass at a bottling plant.

·       Any changes in noise patterns.