Hi Notanotherthing, interesting observation about your hearing.
I get a pulsing sound, that is probably synchronized to my heart rate, when I sometimes change altitude like going up an escalator. At first I thought that there was actually a pulsing sound, but have more recently decided it is background noise turning hearing off and on. Once it starts, it's all over in about a minute. The change in air pressure theory is still under consideration.
Likewise, when you change your head-to-heart vertical distance relationship, there would be a time when the blood pressure in your head changes.
Have you been having regular MRI's (every 6 months in the first 2 years) while on W&W?
How long does your muffling episode last for and does it pulsate?
Hearing deterioration, if I think about it, may be because of:
1) Growing tumor
2) Stable tumor continually squeezing on cochlear nerve or blood vessels
3) Stable tumor releasing toxins
Some of hearing decline is just due to getting older with presbycusis progressing at a rate of about 0.6 dB per year once you reach about 50 years old.
The tried and tested best way of accelerating hearing loss is to have surgery or radiosurgery. If you want to keep your hearing for as long as possible, conservative management is the way to go. ( https://pdfs.semanticscholar.org/2cef/abe8e8eef1ae32cab8bcf3c71dd75f53387c.pdf