This condition is more noticeable at night. For those who suffer from the constant, high pitch ringing in the ears, there is hope, but in the meantime only those who suffer could ever explain the noise. Some say it sounds like a volume of cicadas.
Others mention a high pitch whirring sound that is not so noticeable during the day with other environmental noises, but that high pitch ringing sound becomes more noticeable at night when quietness descents, often disturbing ones sleep.
There are several factors contributing to the ringing noise, one mainly being the lack of iron in the blood and less oxygen, or maybe a head injury? Find the link to the condition so you can get a better nights sleep.