question: Why are humans more or less sensitive to volume at different times during the day?
comment: Noise induced hearing loss, When I worked in a factory, we were not allowed to take hearing test if we had been in the factory that day. It would influence the results. We were told that loud noises would lay the little hairs in your ears over throughout the day and your hearing sensitivity would decrease. When you were removed from the noise over time the hairs would recover and your hearing would return. The ability for the hairs to recover decreases over time and the damage becomes permanent. Here is a link to help explain: URL_0
passages: The phon model can be extended with a time-varying transient model which accounts for "turn-on" (initial transient) and long-term listener fatigue effects. This time-varying behavior is the result of psychological and physiological audio processing. The equal-loudness contours on which the phon is based apply only to the perception of pure steady tones; tests using octave or third-octave bands of noise reveal a different set of curves, owing to the way in which the critical bands of our hearing integrate power over varying bandwidths and our brain sums the various critical bands.
  
  Section::::See also.
  
  BULLET::::- Sone
  
  BULLET::::- A-weighting
  
  BULLET::::- Decibel
   Section::::European guidelines.
  
  The European Union (EU) set up European guidelines in respect to noise pollution. For nighttime, it is advised to not exceed the 40 dB L threshold outside the residence. An interim threshold of 55 dB L is set as an upper bound, because above this limit, (sleeping) disorders are more prevalent. However, about 20% of people living in or near urban areas suffer from sounds at night that exceed even the interim threshold.
  
  Section::::Law in the Netherlands.
   Section::::Prevention.
  
  There are three different methods to address sensory overload: avoidance, setting limits, and meditation. The process of avoidance involves creating a more quiet and orderly environment. This includes keeping the noise to a minimum and reducing the sense of clutter. To prevent sensory overload, it is important to rest before big events and focus your attention and energy on one thing at a time. Setting limits involves restricting the amount of time spent on various activities and selecting settings to carefully avoid crowds and noise. One may also limit interactions with specific people to help prevent sensory overload.
  
  Section::::Marketing.
   A human can see objects in starlight or in bright sunlight, even though on a moonless night objects receive 1/1,000,000,000 of the illumination they would on a bright sunny day; a dynamic range of 90 dB.
   Indeed, a side effect of the reduced visibility is heightened audibility, as soldiers focus more on what they can hear. There are many instances of soldiers losing their bearings at night due to flashes from guns or enemy searchlights. The difficulties of perception lend themselves to fear of the unknown. Soldiers under fire can't tell where the fire originates and can't devise appropriate countermeasures. Such uncertainty is associated with feelings of loneliness and helplessness, and creates a tendency to over estimate enemy strength or be excessively pessimistic of the combat situation.
   Noise has been associated with important cardiovascular health problems, particularly hypertension. Noise levels of 50 dB(A) at night may also increase the risk of myocardial infarction by chronically elevating cortisol production.
  
  Roadway noise levels are sufficient to constrict arterial blood flow and lead to elevated blood pressure. Vasoconstriction can result from elevated adrenaline levels or through medical stress reactions.
  
  Section::::Psychological impacts of noise.
   A 2-minute YouTube video addressing this issue by audio engineer Matt Mayfield has been referenced by "The Wall Street Journal" and the "Chicago Tribune". Pro Sound Web quoted Mayfield, "When there is no quiet, there can be no loud."
   Civil inattention can lead to feelings of loneliness or invisibility, and it reduces the tendency to feel responsibility for the well-being of others. Newcomers to urban areas are often struck by the impersonality of such routines, which they may see as callous and uncaring, rather than as necessary for the peaceful co-existence of close-packed millions.
   Ambient noise is another variable that is conducive to distraction, yet it has been proven that a moderate level of noise actually heighten creativity. Professor Ravi Mehta conducted a study to research the degree of distraction induced by various noise levels and their effect on creativity. The series of experiments show that a moderate level of ambient noise (70 dB) produces just enough distraction to induce processing disfluency, which leads to abstract cognition. These higher construal levels caused by moderate levels of noise consequently enhance creativity.
  
  Section::::Affecting factors.:Walking.
   In March 2010, mastering engineer Ian Shepherd organised the first Dynamic Range Day, a day of online activity intended to raise awareness of the issue and promote the idea that "Dynamic music sounds better". The day was a success and its follow-ups in the following years have built on this, gaining industry support from companies like SSL, Bowers & Wilkins, TC Electronic and Shure as well as engineers like Bob Ludwig, Guy Massey and Steve Lillywhite. Shepherd cites research showing there is no connection between sales and loudness, and that people prefer more dynamic music. He also argues that file-based loudness normalization will eventually render the war irrelevant.
   Manufacturers of sound-masking devices recommend that the volume of white noise machines be initially set at a comfortable level, even if it does not provide the desired level of privacy. As the ear becomes accustomed to the new sound and learns to tune it out, the volume can be gradually increased to increase privacy. Manufacturers of sleeping aids and power-napping devices recommend that the volume level be set slightly louder than "normal music listening level", but always in a comfortable listening range.
   Human diurnality means most people sleep at least part of the night and are active in daytime. Most eat two or three meals in a day. Working time (apart from shift work) mostly involves a daily schedule, beginning in the morning. This produces the daily rush hours experienced by many millions, and the drive time focused on by radio broadcasters. Evening is often leisure time. Bathing every day is a custom for many.
   When sensorineural hearing loss (damage to the cochlea or in the brain) is present, the perception of loudness is altered. Sounds at low levels (often perceived by those without hearing loss as relatively quiet) are no longer audible to the hearing impaired, but sounds at high levels often are perceived as having the same loudness as they would for an unimpaired listener. This phenomenon can be explained by two theories, called "loudness recruitment" and "softness imperception".
   Sudden impulse noises are typically perceived as more bothersome than noise from traffic of equal volume. Annoyance effects of noise are minimally affected by demographics, but fear of the noise source and sensitivity to noise both strongly affect the 'annoyance' of a noise. Sound levels as low as 40 dB(A) can generate noise complaints and the lower threshold for noise producing sleep disturbance is 45 dB(A) or lower.
   The sensitivity of the human ear changes as a function of frequency, as shown in the equal-loudness graph. Each line on this graph shows the SPL required for frequencies to be perceived as equally loud, and different curves pertain to different sound pressure levels. It also shows that humans with normal hearing are most sensitive to sounds around 2–4 kHz, with sensitivity declining to either side of this region. A complete model of the perception of loudness will include the integration of SPL by frequency.
   Later developmental effects occur as vasoconstriction in the mother reduces blood flow and therefore oxygen and nutrition to the fetus. Low birth weights and noise were also associated with lower levels of certain hormones in the mother. These hormones are thought to affect fetal growth and to be good indicators of protein production. The difference between the hormone levels of pregnant mothers in noisy versus quiet areas increased as birth approached.
   Humans also interact with their environments based on their sensory capabilities. The fields of human perception systems, like perceptual psychology and cognitive psychology, are not exact sciences, because human information processing is not a purely physical act, and because perception is affected by cultural factors, personal preferences, experiences, and expectations. So human scale in architecture can also describe buildings with sightlines, acoustic properties, task lighting, ambient lighting, and spatial grammar that fit well with human senses. However, one important caveat is that human perceptions are always going to be less predictable and less measurable than physical dimensions.
   Light pollution is a major issue for nocturnal species, and the impact continues to increase as electricity reaches parts of the world that previously had no access. Species in the tropics are generally more affected by this due to the change in their relatively constant light patterns, but temperate species relying on day-night triggers for behavioral patterns are also affected as well. Many diurnal species see the benefit of a "longer day", allowing for a longer hunting period, which is detrminental to their nocturnal prey trying to avoid them.
  
  Section::::Human disturbances.:Light pollution.:Orientation.
   Loudness is perceived as how "loud" or "soft" a sound is and relates to the totalled number of auditory nerve stimulations over short cyclic time periods, most likely over the duration of theta wave cycles. This means that at short durations, a very short sound can sound softer than a longer sound even though they are presented at the same intensity level. Past around 200 ms this is no longer the case and the duration of the sound no longer affects the apparent loudness of the sound. Figure 3 gives an impression of how loudness information is summed over a period of about 200 ms before being sent to the auditory cortex. Louder signals create a greater 'push' on the Basilar membrane and thus stimulate more nerves, creating a stronger loudness signal. A more complex signal also creates more nerve firings and so sounds louder (for the same wave amplitude) than a simpler sound, such as a sine wave.
   Section::::Practice and sustained attention.
  
  Training and practice significantly reduce the vigilance decrement, reduce the false alarm rate, and may improve sensitivity for many sustained attention tasks. Changes in strategy or bias may improve task performance. Improvements based on such a criterion shift would be expected to occur early in the training process. Experiments involving both audio and visual stimuli indicate the expected training performance improvement within the first five to ten hours of practice or less.
   Even small amounts of environmental light change have shown to have an effect on the activity of mammals. An observational study done on the activity of nocturnal owl monkeys in the Gran Chaco in South America showed that increased amounts of moonlight at night increased their activity levels through the night, which led to a decrease of daytime activity. Meaning that for this species, ambient moonlight is negatively correlated with diurnal activity. This is also connected with the foraging behaviours of the monkeys, as when there were nights of little to no moonlight, it affected the monkey’s ability to forage efficiently, so they were forced to be more active in the day to find food.
   Climate-change and the change in global temperatures has led to an increasing amount of diurnal species to push their activity patterns closer towards crepuscular or fully nocturnal behavior. This adaptive measure allows species to avoid the heat of the day, without having to leave that particular habitat.
  
  Section::::Human disturbances.
  
  The exponential increase in human expansion and technological advances in the last few centuries has had a major effect on nocturnal animals, as well as diurnal species. The causes of these can be traced to distinct, sometimes overlapping areas: light pollution and spatial disturbance.
  
  Section::::Human disturbances.:Light pollution.
   Section::::Lack of habituation.
   The U.S. Environmental Protection Agency has identified the level of 70 dB(A) (40% louder to twice as loud as normal conversation; typical level of TV, radio, stereo; city street noise) for 24‑hour exposure as the level necessary to protect the public from hearing loss and other disruptive effects from noise, such as sleep disturbance, stress-related problems, learning detriment, etc. Noise levels are typically in the 65 to 75 dB (A) range for those living near airports or freeways and may result in hearing damage if sufficient time is spent outdoors.
   One of the biggest factors that affect active space size will be the "[water conductance]" mediated by solute concentration in the water. It's been shown that momyrids have adapted its optimal active range in lower-conductivity habitats. One natural phenomenon that supports such theory is that, many species spawn during the time when rivers/ lakes have the lowest conductivity due to heavy rains. Having bigger active space in water with low conductivity will therefore benefit mating and courting. One other explanation tested by Kim and Moller is that, having smaller active space during dry season when mating is not occurring accommodates crowded social spacing without unnecessary signal transmission between individuals.
  
raw_presuppositions: Sensitivity to sound should always be the same.
raw_corrections: Little hairs in your ear the help you hear are damaged by loud sounds. This causes a different sensitivity to sounds. 