hello and welcome to HCM,
A hissing in the ear along with fullness in the ear can be suggesting many causes all centering on to your ears or rarely brain/ Sinuses
you need to do the following:
1. Get a full neurological work up including CT/ MRI
of the brain to rule out any major issues
2. Get a full ENT consult and get your audiometry
and CT of the brain/ Temporal bone
done to rule out the contribution of the ears in your malady
Just remember that the test which caused fullness in your ears is called impedance and is a very reliable test. Also your audiometric analysis is important to rule out any hearing loss
and also for further follow up.
You need to also rule out any sinus problem which can aggravate your ear block and cause the noise.
take care and get well soon
Dr Sriram Nathan