Is it possible for your ear's frequency response to change throughout the day?

I've just recently been noticing that my ears' response to low frequencies is much less sensitive in the morning than it is at night. I currently have a tune with a very big, boomy kick in it that sounds insane through the cans when I'm listening at night, to the point where I think I'm going to have to reign that in a bit. So in the morning I'll slap the cans on again and actually think about turning it up because it just doesn't sound powerful enough. I've sometimes noticed that bass parts sound quieter in the morning than they did the night before. This is something I've noticed in my headphones, which have quite good isolation so I don't think it's a case of quieter surroundings at night. Could it be that my ears' low frequency response takes some time to "warm up" after I wake?

I work in the optometry business. Blood sugar plays a big role in your eyesight, and how your visual acuity changes throughout the day. It stands to reason that it would affect other senses too.

Interesting about the eyes because I've often noticed that when I wake up and look at the wall in front of me through one eye and then the other, each eye sees a slightly different color. I've tried it later in the day and don't see a difference. 
 
Yeah Bit I don't hear anything over 16kHz either. Screw those frequencies!

I'm guessing not your thumb..................

Absolutely.... I don't listen to any music in my ear buds until I'm up for at least an hour or so. Radio is different....anything with speakers is fine as long as it's not critical listening.....I tend to review songs on the forums in the mornings..... what does that tell you?
 
but yes, I notice the same thing.... a noticeable lack of bass response on the buds or cans. So being aware of that, I don't do final mixing in the very early mornings. I let the day roll on a few hours and then mix.

I'd read that it's mainly the upper frequencies that are affected, but I had an experience yesterday that made me question that.
 
The night before, lying in bed with my best headphones on I listened to a mix and made a mental note that there wasn't enough bass in the mix. Next morning as soon as I awoke and before getting out of bed I grabbed the cans and listened to it again. My early-morning evaluation was "what was I thinking last night? There's plenty of bass."
 
There is one other variable that deserves mention, and that is the presence of tetrahydrocannabinol during the previous night's audition. There is no doubt that marijuana affects sensory perception, but I would have assumed its effect would be a heightening of sensitivity. This experience suggests the opposite may be true.
 
But considering how many classic records had marijuana as an ingredient, could it be that deadening frequency perception might be a good thing? Does it perhaps lead you to make more dramatic mix decisions such as gobs of bass or super-compressed drums? The first guy to stick a $1000 microphone an inch from a drum had to have been smokin' something.

bitflipper
 The first guy to stick a $1000 microphone an inch from a drum had to have been smokin' something.

or just a $600 Beyer M160 ribbon on a snare....  which is probably the 2nd most popular mic used for that, back when...  Probably threw a TV set out the window, that same day.

Sidroe
Your hearing can change in a matter of seconds depending on how you subject your ears to db and air pressure levels. Do a google on ear fatigue. I learned what little I know from a high school bud that went on to med school and is a practicing ear doctor. Based on what he told me I drastically reduced my levels and TIME spent under headphones! I just turned 62 two weeks ago. I have been suffering from tinnitus going on about 30 to 35 years. I attribute it to standing in front of a Marshall Super Lead 100 watt stack all those years in clubs and on the road.
I have set guidelines now in my studio work producing that I never track and mix on the same day. Mixing at high levels never lasts more than a couple of hours at most. Headphones may be used for tracking, never mastering. If it still isn't right, I try again the next day. No deadline is worth your hearing!
I, too, have lived in apartments where you had no choice but headphones. Just try to be very judicious volume and time wise underneath those things. I don't know what your age is but I can tell you, I sure would have taken better care of my hearing back then. I am paying for it now.

I too have tinnitus, had it since my 20's. Am not sure exactly when it started, I think it just crept up on me but I was too stoned to notice. In my case it was a combination of being in thrash bands when I was younger, then dancing high as a kite to acid trance music for 12 hours straight in front of huge speakers at illegal raves for much of the early 90's. Oh and a few Metallica/Slayer/Dio gigs in the late 80's. Not to mention the long hours spent listening to Frank Zappa on headphones. Considering all of that though, I think my hearing has fared pretty well. I can't hear much over 15-16k but that's common for my age (41). 
 
I use headphones a lot (both at home and in the gym) but I try to keep the volume reasonable and I always stop at regular intervals and have a 10 minute break. One thing I've been doing for the past year, and I'm sure many will think I'm mad, but I've been taking a good magnesium supplement (i.e. not oxide) a couple of times a day. This was after reading from multiple sources that it can protect the ears from noise damage. Well before doing any work on headphones in the evening, I'll take a couple of chelated magnesium pills ("Doctor's Best" brand) and drink some Natural Calm, a magnesium drink which also really helps me relax in the evenings and melts away the tension. It's not a substitute for avoiding loud noise, but I figure that as part of a regime of noise caution it can only help. I've also heard that resveratrol is touted as a protection against hearing loss, so it'll be interesting to see how those studies go.
 
New York is one hell of a noisy city. I'm out and about on the streets of Manhattan most days and you're constantly bombarded with sirens, construction noise and of course the deafening subways. I always stick my fingers in my ears when a train goes past, especially when they're applying those horrible squeaky brakes. Looking around I see that hardly anyone else does it, which is a shame considering how many times New Yorkers have been told how potentially damaging subway noise is. God knows what it's doing to kids.  

440 pages..that looks like quite a read. I could go for something funny.