These tests are usually performed instead of a traditional catheter angiography, which is more invasive and, while generally very safe, carries greater risk of complications. Angiography is an imaging technique that involves injecting dye into a small tube called a catheter that has been inserted into a blood vessel. An x-ray is then performed to assess the health of the vessels as well as the rate of blood flow.

The noise heard by people with tinnitus may be a buzzing, ringing, roaring, whistling, or hissing sound and is often associated with hearing loss. Some people hear more complex sounds that may be different at different times. These sounds are more noticeable in a quiet environment and when people are not concentrating on something else. Thus, tinnitus tends to be most disturbing to people when they are trying to sleep. However, the experience of tinnitus is highly individual. Some people are very disturbed by their symptoms, whereas others find them quite bearable.

Cartoon of the middle ear showing muscles that attach to ossicles (ear bones), and ear drum. The stapedius is attached to the stapes (of course -- horseshoe object above), while the tensor tympani is attached to the ear drum. While useful, be aware that there are multiple errors in this illustration from Loyola Medical School. With permission, from:
It is important to note that existing hearing loss is sometimes not directly observable by the patient, who may not perceive any lost frequencies. But this this does not mean that hearing damage has not been done. A trained audiologist or other hearing health professional can perform sensitive audiometric tests to precisely measure the true extent of hearing loss.
Millions of Americans experience tinnitus, often to a debilitating degree, making it one of the most common health conditions in the country. The U.S. Centers for Disease Control estimates that nearly 15% of the general public — over 50 million Americans — experience some form of tinnitus. Roughly 20 million people struggle with burdensome chronic tinnitus, while 2 million have extreme and debilitating cases.1