This article is about entrainment of the Circadian Rhythm of a normal healthy adult male in constant dark conditions using discrete noise as an environmental stimulus (zeitgeber).

Case Study:

A normal healthy adult male, living in the same dwelling for more than 30 years with not a single night’s sleep lost. Occasionally, twice a year approximately and only on the nights he had been drinking alcohol, he would wake in the early hours of the morning to empty his bladder and return to bed and sleep very quickly. He also stated that he dreamt a great deal.

For over 16 years the method by which he was woken was an ordinary radio alarm clock, which never failed to wake him, and he was never awake before the alarm went off. In the early hours of 21st December 2000 (5:00am) he was awake, wide awake, and could not get back to sleep. The following night, he was woken three times, each time he lay in bed and then went back to sleep in approximately two minutes. This situation carried on for three months, waking two, three, or four times each night. The situation eased a little after three months.

Throughout this period he explained of being woken up in a very strange way as he would wake up with his eyes still shut. He was so disorientated by this that he would ask himself (in his head) if he was awake, and answer it (by thinking) ‘open your eyes and find out’, he did, and he was.

Twelve months later the situation was no better, a short discussion with his neighbour resulted in a significant change in sleep pattern, five, full uninterrupted nights sleep, waking at approximately 6am, after which the disrupted sleep pattern then returned. Further approaches to his neighbours, by the subject, and by another occupant of the same dwelling also resulted in a significant change in sleep pattern. Both occupants of the neighbouring premises stated that they were asleep. The subject was completely unaware of any noise.

A complaint was made to the local council, whose responsibility it is to investigate noise nuisance within its area. A noise investigation was conducted by acousticians, and equipment was supplied called a ‘matron’ box, which was equipped with a Digital Audio Tape recorder, electronic time stamp device, external microphone and a push button. The subject was instructed to press the button when woken, record the noise, and press the button again to stop recording. This was done for one week, an acoustician returned to collect the equipment and the log which the subject had made. Analysis of the recordings showed that the equipment was operated correctly, but no noise was recorded on the equipment that suggested it would cause sleep disturbance/disruption.

The subject used a standard VHS video recorder to record any noise in his bedroom all through the night, and after listening to this recording the subject asked the acousticians to return and identify one very specific noise. The acousticians also listened to the noise recorded by the subject, they identified some of it as noise through a party wall, but dismissed it due to its level, they then tested and measured the levels of several electrical switches in the neighbouring premises. The subject clearly identified, after an audible comparison the operation of an electrical switch, but this identification was ignored by the acousticians. It was clearly stated that the noise levels measured from the operation of an electrical switched socket in his neighbour’s bedroom would not wake up a normal or average person (using World Health Organisation Guidelines). They did not consider frequency content, nor duration.

The situation subsequently got much worse, subjecting this person to three or four hours sleep loss per night over a period of six months. A further noise investigation was conducted, this time with noise level monitoring equipment in the neighbour’s dwelling. The equipment was placed in the neighbouring dwelling without the subject’s knowledge, but he was asked to continue to log his sleep disturbances. The subject’s sleep loss totally disappeared, leaving very mild disturbances of sleep each night. The equipment was removed, again without the subject’s knowledge and the three to four hours sleep loss per night returned.

This paper aims to inform and remove the prejudice and stigma attached to people who suffer such disturbances of sleep, and present a case for more research into this field by Chronobiologists and Sleep Researchers, to establish problems such as these as environmental, instead of medical.

The Environmental Stimulus:

In the period prior to the subject’s arousal, several pulses of noise were identified. One of the noises (Fig. 1) was identified as being through a party wall, having a duration of 250ms, and a frequency of 70Hz decaying to 55Hz, the amplitude could not be established. A 70Hz waveform (Fig. 2) is shown for comparison.


Figure 1. 70Hz – 55Hz waveform, 250ms (a quarter of a second).


Figure 2. 70Hz waveform.

The second of the two noises (Fig. 3) was identified as the mechanical operation of an electrical switch. The operation of this switch caused vibration to pass through the structure of the building four metres from the sleeping position, and produce a noise measuring 39.7 dB(A) at the sleeping position, with a duration of 50ms, and complex frequency content ranging from 86Hz to 21kHz.

The noise level was determined with the equipment supplied by the local council, however the waveforms, frequency content and duration were all established from the VHS video recordings the subject had made. The make and model of the video recorder used was a Panasonic NV-HD 100 ideally suited because of its microphone input and gain control. The subject was trying to establish the existence of noise and its source, the noise levels were not his primary focus.


Figure 3. Electrical Switch, complex in waveform, and in frequency content 50ms (a twentieth of a second).

These two noises will now be referred to as stimulus 1 (250ms noise) and stimulus 2 (50ms noise). To an untrained individual these noises may be considered as trivial, however, everyone knows that noise does in fact wake a person from their sleep. An alarm clock is the best example of this. It must be made very clear that the noises recorded occurred anything up to 40 minutes prior to the subject waking from his sleep, he was therefore unaware of their presence. How could these noises wake up the subject and what part of the brain do they affect in order to accomplish this?

The Circadian Rhythm:

In order to understand ‘Entrainment’ of the Circadian Rhythm you first have to understand what exactly is the Circadian Rhythm. The Circadian Rhythm is a clock, and because it is buried within the brain, it is called a ‘Biological Clock’.

Our daily lives revolve around clocks, when to get up in a morning, when to set off for work in order to miss rush hour traffic, the time you start work, the time you eat lunch, the time you leave work. It would be difficult to understand a world without a clock to govern where we should be and what we should be doing.

The ‘Circadian Rhythm’ is an internal clock, governing the brain and body’s activities, it can however be altered by the food you eat, the beverages you drink, the air you breathe, the drugs you take (prescribed or otherwise), it is also altered by the light/dark cycle of a normal 24hr day.

It may be of interest to know that the internal clock of an expectant mother is different to that of her unborn child. When the child is born its internal clock is not synchronised with its new environment, it therefore takes several months for the child’s biological clock to entrain (synchronise) to its new environment. Its new environment being that of the 24hr light/dark cycle, however with darkness comes the inevitable, bedtime, and with that silence.

The field of Sleep Research states that noise changes the depth of sleep from deeper to lighter levels of sleep, noise does therefore affect the ‘Circadian Rhythm’, it does not satisfactorily describe what happens next.

The field of Chronobiology does not specify noise as a stimulus that affects the ‘Circadian Rhythm’, it does however state that pulses of stimuli that affect the rhythm cause ‘Phase Shifts’ (changes to the free running rhythm).

Entrainment is difficult to define because there are a vast array of stimuli that can affect the ‘Circadian Rhythm’, however where sleep is concerned the subject’s rhythm and environment were synchronised (correctly entrained to the environment), he would not take short naps during the day and he would sleep without interruption during the night. When the subject’s sleep disruption started his rhythm became partially unsynchronised, due to the noise he was exposed to. Entrainment where sleep is concerned can be defined as moving the ‘Circadian Rhythm’ from its free running in constant dark conditions, where the person is unconscious to its free running in constant dark conditions, where the person is conscious. The stimulus used to do this would be noise.

The ‘Circadian Rhythm’ can be altered by noise, noise is therefore a zeitgeber (from the German for “timegiver”) and it is this method of entrainment by noise that is of interest, and the very important question, what is a ‘Silent Night’?

When a person goes to sleep, they do not sleep at the same depth throughout their slumber, the ‘Circadian Rhythm’ follows a set pattern. This pattern (Fig. 4) goes from REM Sleep (Dreaming, and the lightest form of sleep), through stages 1, 2, 3, 4, and then returns to stages 3, 2, 1, REM, this cycle is called an ‘Ultradian Rhythm’, it is usually 90 to 100 minutes in duration and repeats several times throughout the night. The longer the person is asleep more time is spent in REM Sleep, and less time in stages 4, 3, and 2.

The pattern of sleep shown in Figure 4 is very similar to that of the subject’s prior to 21st December 2000. The subject knew nothing else, he would sleep solidly each and every night, waking to the sound of his radio alarm clock and remembering very vivid dreams.

Figure 4. Circadian Rhythm in constant ‘Dark’ and ‘Silent’ conditions (free running).

Figure 4. Part of the Circadian Rhythm in constant ‘Dark’ and ‘Silent’ conditions (free running).

The path the ‘Circadian Rhythm’ takes, shown in Figure 5, is however somewhat different. This is due to the pulses of discrete noise that occurred at 12:08am and 12:15am whilst the subject was sleeping. These pulses of noise cause phase shifts to the ‘Circadian Rhythm’ (small changes in the depth of sleep). Any individual who is subjected to this noise would be completely unaware of the noise and completely unaware that their sleep pattern has been altered.

Pulses of noise similar to stimulus 1 (250ms noise) and stimulus 2 (50ms noise) would be dismissed by an untrained individual, as would recording the noise and playing it back.


Figure 5. Part of the Circadian Rhythm, showing discrete noise events occurring at 12:08am, and 12:15am, the subject will wake at approx 12:27am.

Further intrusions of discrete noise into the sleeping environment (Fig. 6) will result in the rhythm crossing the threshold of sleep several times throughout the night.


Figure 6. Showing multiple intrusions of discrete noise, the subject would wake several times throughout his sleep and was completely unaware of any noise.

It should now be clear that the pulses of noise that intruded into the subject’s sleeping environment altered his sleep pattern (Circadian Rhythm) causing recurrent states of consciousness.  In the profession of psychiatry this is called ‘Circadian Rhythm Sleep Disorder’.  An environmental noise nuisance is called a disorder.

The sleep pattern shown in Figure 7 is a very clear representation of what the subject had to suffer over a period of six months, after the first noise investigation was concluded.  The health of the subject suffered incredibly. In the profession of psychiatry this is called ‘A Sleep Disorder to indicate a General Medical Condition’. An environmental noise nuisance would then be medicated by a psychiatrist, without the patient ever knowing the underlying cause of the problem.


Figure 7. When the activity from neighbouring premises increases, the number of discrete noise events also increases, each noise is cumulative when it occurs within the same Ultradian Rhythm, ie it acts on the affect from the previous noise event.

The subject’s Circadian Rhythm has been successfully entrained into the dark environment where he is fully conscious and completely unsynchronised with what would be normally expected.

A very clear correlation can now be established between the following:

a) Circadian Rhythm Sleep Disorder
b) Entrainment of the Circadian Rhythm

There is one further correlation which also needs to be considered at this time, that is current UK Legislation on noise nuisance which defines a nuisance as ‘noise emitted from premises so as to be prejudicial to health or a nuisance’.

During the second noise nuisance investigation the subject slept considerably better and was then subjected to more sleep loss (10 hours sleep loss in just three nights). The psychological stress placed upon the subject by having his sleep returned to him and then removed again, with no explanation as to why were far too great and the consequences too horrifying to describe.

On the 22nd December 2002, twelve days after the second noise nuisance investigation concluded, the subject’s sleep loss vanished, leaving very mild disturbances of sleep. These disturbances of sleep were so mild that each time the subject woke he remembered a dream.  In the field of Sleep Research this is called ‘REM Rebound’ and it happens when the perturbing factor, in this case the noise from the subject’s neighbours, is removed.

The Circadian Rhythm synchronises to its environment.  The noise which was intruding into the subject’s sleeping environment was altering the subject’s internal clock in the same way that an alarm clock is designed to.

In order to better understand the Circadian Rhythm it must be established which of the two noises, identified early as stimulus 1 (250ms noise) and stimulus 2 (50ms noise), alters the internal clock and that very important question what is a ‘Silent Night’? must be answered.

The K-Complex and K-Alpha:

The terms ‘K-Complex’ and ‘K-Alpha’ are not chronobiological terms, they are in fact sleep research terms which have a very strong association to this case and therefore must be covered.  The sleep pattern with the stages of sleep are shown in Figure 8.  Whilst the subject was sleeping and progressing through the stages of sleep the subject’s brainwaves (EEG waves) also changed.


Figure 8. Sleep stages and brainwave activity within those stages.

Brainwaves can only be monitored by means of an electroencephalograph (EEG), however brainwaves can be altered by noise.  A ‘K-Complex’ is a sharp change in brainwave activity and is caused particular by auditory stimuli.

The subject described himself as being woken up in a very strange way, he would wake up with his eyes still shut.  This could also be described as ‘a twinkling of an eye’. A ‘K Alpha’ is a K-Complex followed by ‘Alpha’ brainwave activity ie the subject is in a relaxed awake condition with his eyes closed, it therefore follows that in order for a ‘K-Alpha’ to exist two very distinctive noises must be present in the sleeping environment.  One of the noises must evoke changes in brainwave activity causing a ‘K-Complex’ and the other noise must change the depth of sleep.

It is very important to determine which of the two noises, stimulus 1 (250ms noise) and stimulus 2 (50ms noise) caused which affect.  In order to establish this the environment that the subject slept in needs to be examined, shown in Figure 9.


Figure 9. The subject’s bedroom and furniture.

The environment that the subject slept in was very comfortable for the subject, his bedroom being at the rear of the dwelling.  The electrical items that were in his bedroom were all switched off whilst he was sleeping, except two.  These two being his radio alarm clock and his video recorder.  The video recorder could be programmed to record in the middle of the night, it would start, record, and stop without ever waking the subject.

The bedroom window would be open at night through the summer months and the subject’s sleep was not disrupted even though the traffic from the main road at the front of the dwelling could be heard.  In the winter months the window would be closed at night, however neither the rain on the window nor the wind would disrupt the subject’s sleep.

The subject’s own bedroom was comfortable and suitable for sleeping in, Figure 10 shows the relationship between the subject’s bedroom and his neighbours bedroom.

Whilst the subject and his neighbours were on reasonable terms a discussion took place between them.  The neighbour pointed out several electrical sockets that were not working, they were all charred and scorched on their face plates, electrical socket B in Figure 10 is one of these.  The neighbour then proceeded to explain and point out an electrical heater, the cable of which got ‘very hot’ when in use.  It can only be assumed that the electrical heater was in fact faulty, this was then used in electrical sockets until the socket was damaged and would no longer work, at which point the electrical heater was used in another electrical socket.  Electrical socket A was in fact the only electrical socket working on this floor in the neighbours dwelling.


Figure 10.

The Local Council measured the noise level in the subject’s bedroom whilst electrical socket A was operated, noise did in fact come through into the subject’s bedroom, however the acousticians determined that it was not loud enough to disturb the sleep of a normal or average person and duly informed the neighbours of this.

Shortly after the Local Council had walked away from a very serious problem the subject took a very radical step.  The subject knew that in some way his neighbours activities were waking him up, he knew that the electrical switch was being used in the middle of the night and that his awakenings were connected to this switch.  The very radial step that the subject took was to remove clothes from three draws and half the clothes from his wardrobe and pile them up against the chimney breast and wall.

There was an immediate change to the subject’s sleep, he would still wake up, but was not woken as severely as before.  There was also another very distinctive change, he was no longer woken with his eyes closed.  It can therefore be determined that the pile of clothes successfully blocked the noise that occurred when the electrical switch was operated.  Stimulus 2 (50ms noise) was responsible for causing a ‘K-Complex’.

The conclusion that stimulus 2 (50ms noise) measuring 39.7dB(A) caused a sharp change in brainwave activity leaves a perplexing situation.  It therefore means that stimulus 1 (250ms noise) which was in fact quieter, is the noise responsible for changing the depth of sleep (causing a phase shift).

The manner in which the noise was assessed by the Local Council must therefore be incorrect, and relying on the amplitude of a noise to determine the existence of a nuisance is scientifically flawed.

In order for the subject to sleep uninterrupted throughout the night, the sleeping environment must be absent of any noise which can be established as meeting the criteria of a zeitgeber (time giver).  This defines in chronobiological terms a ‘Silent Night’.

A Silent Night:

There are however historical and theological aspects to defining a ‘Silent Night’ and these also need to be covered to fully comprehend the situation.

There are many variations to the hymn ‘Silent Night’, one of those is:

Silent Night! Holy Night!
Darkness Flies! All is light!

This, at first thought, may seem like a trivial association. However, darkness did indeed fly for the subject each and every night until 21st December 2000. There are, furthermore, additional significant associations.

The subject states “I committed a sin of the flesh on the 6th January 2001”. This statement brings into focus two very significant theological associations.

The subject would not go in to detail regarding what he meant by ‘a sin of the flesh’. However, he did state that it met the criteria of what was described in the Holy Bible, King James Version, 1 Corinthians 6.

The second significant association is the date, 6th January, which is the Epiphany: an ancient Christian feast day celebrating when God revealed himself to the world through the re-incarnation of Jesus.

The sinful act, and the date on which the subject committed that sinful act both have very significant historical and theological associations. Are these the only two associations or are there more?

The subjects sleep disruption started on 21st December 2000. Do these two, the sleep disruption and the date, also have theological significance?

We are all taught from an early age that our actions have consequences. The subject believes that the sleep disruption that started on 21st December 2000 is a divine punishment for the sin of the flesh that he committed on 6th January 2001. This belief would put the consequence before the act. It is therefore necessary to establish if the sleep disruption and the date on which it started have any theological association.

In the Holy Bible (King James Version), 1 Corinthians 15:31 states “I die daily”. The subject did indeed die daily, without any disruption to his sleep and awoke to righteousness, because he had not sinned. It is also important to bring into focus other parts of the Holy Bible, like 1 Corinthians 15:56 where “the sting of death is sin”. If the same interpretation is applied to this, then the statement becomes the ‘sting of sleep is sin’, this supports the subject’s belief that his sleep disruption is punishment for the sin which he committed.

The subject’s sleep disruption started on 21st December 2000, and there does not seem to be any association with this date until you look deeper and farther back in history. The 21st December has significance in the Mayan long count calendar with the prophecies of a new spiritually enlightened era beginning in 2012. There is, therefore, clearly a most definite association with this date.

Scientific Summary

The pulses of discrete noise which intrude into a person’s sleeping environment will disrupt that individual’s Circadian Rhythm, thereby altering their depth of sleep. The person will wake, but when they wake is dependent on how much the noise altered their Circadian Rhythm and how much of the Ultradian Rhythm cycle remains.

The environmental health officers who investigated this case are acousticians. They assessed the impact of noise on the Circadian Rhythm, which is a biological mechanism outside of the acoustician’s discipline. The law did not require them to (specifically or consequentially) assess the impact of noise on a human being, but, in this case they did, with the result that they destroyed the physical and mental health of a human being.

The noise which caused sleep disruption in this case was emitted from neighbouring premises. All of the subject’s family instinctively knew how to act in the middle of the night when others were sleeping, like closing doors extremely quietly, or treading on the floor quietly.

Sleep disruption in other families may not, of course, be caused by neighbours. It might just as easily be caused by individuals in the same household.

Theological Summary

In this case the subject believes that his sleep disruption is punishment for the sin which he committed, and there is strong evidence to support this, with associations in the Holy Bible.

The subject also believes that shortly before any person commits a sin of the flesh, their sleep is also disrupted by noise and their silent night is removed from them.

This perfect and divine punishment exploits ignorance, as it is a situation where the punishment starts BEFORE the sinful act, and the person is unaware of any noise.

Did you sleep through the night, and without any disruption to your sleep?
Or conversely, when did your sleep disruption start?
When did you commit a sin of the flesh?
It is a belief which has been explored, and which can be proven.