I was listening yesterday for over 10 hours straight. It sounded awesome at first, then I thought the sound really deteriorated. I even went to MediaMonkey to play my mp3s. This time I did find a problem. I fixed it and wow again, but some days my system blows me away and other days lacking and nothing technically has changed. My own biological clock has been ticking for a lot of years. I remember the Heathkit and my crystal radio. Lol!
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Our senses can change a bit day too day and even during the same day due to exposure to outside stimuli. Foods or wines especially may taste different, your sense of smell makes something seem to have a different odor or is less sensitive. Happens to our ears as well. Just don’t particularly notice it with every day sounds were critical listening is not important. Welcome to the human race.
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Thanks for the explanation! I was wondering why my music sounds so dry now. I’ve been living in Arizona for the last five years. 
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I’m not a doctor, but another possibility to consider is biological. Our ears can most definitely change during the course of a day with allergens being one of the biggest offenders. Without knowing it, inflamed eustachian tubes can muffle sound. When this happens, I try pinching my nose and blowing inwardly to relieve pressure. Antihistamines and decongestants can also help with this. And for those over 50 wax buildup in the ear should be checked by your doctor. Whether it’s atmospheric, electrical, biological or another factor that seems to be changing sound quality, listening to music is one of the joys of life. So when one day it sounds good I crank it up and another day not so much I turn it down and remember how good it could sound tomorrow!
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I have noticed that all systems I have owned have sounded better in wet atmospheric conditions that dry. I have put this down to the quality of the earthing of the components being “improved” when wet outside.
I think what you perceive is affected a lot by factors like tiredness, stress, general mood etc.
The whole ear brain thing is complex. One of the most obvious likely causes is little muscles in your middle ear that are there to serve as sound limiters/compressors (ie protect your hearing from loud sounds). If they are a little tense for any reason, then what you will have diminished hearing. Blood flow to inner ear is belived to have an impact as well.
If you have been listening at a moderate level for a while then as we age, our tolerance to noise diminishes as well (exposure time and SPL), so we fatigue sooner and need more quite breaks as a ‘reset’ to restore normal sensitivity. Anyone who has worked in audio production is probably already acutely aware of this.
I would agree with atmospheric conditions as well, I guess pressure and humidity impact air density. I still think the biggest impact is your own state of being which is affect by atmospheric conditions as well.
Also position in the room, proximity to seat/sofa backs, walls etc, posture etc - all can have a significant impact.
All these are why even ABX testing can be hard unless properly controlled.
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I’m no fan of ABX testing, precisely because of the fatigue issue. With very subtle differences, I find it impossible to maintain focus to the point of statistical significance. Perhaps if you spaced out the comparisons it would work.
@Rob_Melone, good point. I certainly get wax buildup periodically and that impairs my hearing. I also have allergies and it never occurred to me that they might be interfering with my hearing.
The fatique I mention is about the little mechanical compressors in your ears eventually kicking in to dampen the sound.
Mercedes Benz takes advantage of this with their Pre-Safe system.
Basically, you get this burst of noise out of your car stereo when the car senses an imminent crash, the muscles in that part of the inner ear contract, and this keep those parts from getting banged around during the crash.
Genius.
I think there are a number of factors at play, chief of which have already been mentioned, i.e., electrical supply fluctuations, ‘grunge’ on the mains from a lot of other noisy equipment (late night listening is often very good) and mood of the listener - listening is psychoacoustic, after all, and therefore emotional state and fatigue, or lack of, all play a part.
There’s one which hasn’t been mentioned, though. Fluctuations in seismic activity. Sounds mad, I know, but look up Townshend Seismic Podiums, and the reasoning behind why they make such a dramatic difference - https://youtu.be/dW9-r83IvhI it’s all interesting stuff, but the explanation of the effect seismic activity might have on a system begins at around 3:00 mins.
I’ve never tried the podiums myself, but I find the theory fascinating and they seem to get rave reviews everywhere.
My personal experience is that noise in the mains supply itself, plus noisy appliances and power supplies in the home are a primary cause of the fluctuations we hear. SQ usually seems better late at night than during the day for me. So, recently I set about looking at the ‘best’ (aka affordable) solution I could come up with to address this at a system level.
After a good amount of research and discussion with colleagues who experience the same phenomenon, I picked up a Blue Horizon Mains Noise Analyser and borrowed a IsoTek Aquarius Mains Power Conditioner and Filter. The Noise Analyser can be plugged into any wall outlet, powerstrip or device mains power outlet and provides a parts per thousand read out of ‘noise’ in the mains power chain. It was interesting to find that I got quite different readings from the same socket, depending if I measured during the day, or late at night, with night time readings almost always being lower than daytime readings.
Next I installed the IsoTek Aquarius, which has 2 x 16 amp outlets for higher power devices such as power amps and 4 x 10 amp outlets for lower power devices such as DACs, Pre amps and Streamers etc.
Plugging the Noise Analyser directly into the wall socket that services my Hi Fi gear, I get a day time reading of 375, which is the medium/moderate mains noise range. Plugging the Aquarius into the same mains outlet and then plugging the Noise Analyser into one of the 16 amp outlets of the Aquarius, the mains noise reduces to 009, which is in the very low range.
Next step was to plug each piece of kit into the one of the 16 amp outlets on the Aquarius, with the Noise Analyser in the other 16 amp outlet. This allowed me to see what effect each piece of kit and, importantly, its accompanying power supply, had in introducing mains noise back into the system. Most of my devices added either 0 or just 2 to 3 points to the baseline measured 009 output of Aquarius, with the notable exception of a Power adaptor for a USB power supply. Plugging this 9v output SM power supply in gave me a reading of 476 on the Noise Meter, that jumped up to 650, when I plugged the USB power supply into it and powered on!
I was using/planning to use the USB power supply to power my Chord DAC and Hattor Passive Pre Amp, but given this result, elected instead to use their own respective power supplies, which did not increase the baseline 009 noise level of the Aquarius output. In the meantime, I am in discussions with the USB power supply company to resolve what seems to be an issue with the USB power supply itself and/or the 9v SM power supply that feeds it.
So, what was the result of adding in the Aquarius unit and removing the USB power supply??
Overall a big improvement in SQ, when compared to the unconditioned/unfiltered system I started with. A much lower noise floor, where instruments were far better separated and notes seemed to have nuances at their start and in their decay that I hadn’t heard before. The intro to ‘Limehouse Blues’ on the DSD version of ‘Jazz at the Pawnshop’ for example the crowd noises seemed much more realistic, natural and detailed and I could pick up the extra detail at lower volume levels. Likewise, Diana Krall’s intro vocals on the 24bit/192 version of ‘Like Someone In Love’ from the ‘Turn Up The Quiet’ (kinda ironic!
) album, revealed inflections in her mouth opening before any voice came out, that I had just not heard before.
Then there is, of course, the consistency this brings to ‘when’ you listen. Now I find it much more enjoyable to listen during the daytime than before and it’s difficult to really hear any difference. Perhaps I still do enjoy listening more at night, but I’ve put that down to the glass of wine!
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The definition of ‘high’ varies from person to person 
Not generally a problem we have here in the UK, or least it wasn’t until they started fracking all over the place…
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Ever thought about the acoustic proerties of dry air vs wet air ?
Sound is after all nothing more then mudulated air pressure. We humans are used to hearing modulated air. You probably know the effect on a human voice after inhaling from a Helium balloon. Sounds funny to us but it is the same modulation that is taking place. Nothing changes on your vocal cords, they just modulate a gas with different properties.
The same holds true for the properties of the air, although much more subtle then changing gasses it does have an effect on perceived sound. In the PA world it is common practice to compensate for air conditions. A large PA in a stadium sounds different when humid condition change. Modern PA system compensate for that. There is no such thing like “improved earthing” going on here.
In most city areas it is a ferrytale based on speculations that the electricity is better during late hours then by daytime. During the evening there is a peak in electricity usage from Microwave ovens, washing machines, computer, lightning, tv’s, heavy industry and in these modern days, car battery, electric bike battery loading. In other words, everything people do when they are at home. Most people consume much more electricity while at home then at work. Years ago I have measured my mains intensively during a period of weeks and it turns out it is by far the cleanest during daytime. And yes, my setup also sounds better during the evening, even better late at night. In both times the mains polution was a lot higher then during daytime.
…but the humidity inside the house doesn’t change significantly (I have hygrometers). As we all know, good earthing is essential for high quality hi-fi equipment so I haven’t quite given up on that theory yet.
Thanks for your post. Not sure if in practice it will make an audible difference, for me at least, but I am intrigued.
Kevin Deal of Upscale Audio has a video about this unit.
Yep, and it really does do that! I was always skeptical about clean power making a difference, but then got to thinking about it more, primarily due to the phenomenon of your system sounding different day to day / time to time, that started this thread off.
If i had my time over again, I think I would prioritise getting my mains power as clean as I (affordably) could, before getting into a lot of upgrades, as the more revealing you make your system, the greater the chance of mains noise being revealed. I really was s bit of a skeptic, but borrowing the equipment and trying it out definitely made me rethink the value of mains conditioning and filtering
I have owned a PSaudio powerplant (till it died on me) and even with this regenerator music sounds better in the evening and even better late at night. Yes, power conditioning helps for your sound but the “power is cleaner in the evening” is a fairytale. Even the electrical compagnies over here warn for the fact that they soon have a capacity problem during evening hours with more and more electric appliances in evey household and more and more electrical vehicles charging and electrical cooking instead of gas. In my area the power has the highest polution between 18:00 and 22:00, right at the hours where most people are at home. And this was measured four years ago, the situtation is probably even worse nowadays