A friend of mine, a retired foundary manager and science enthusiast, recently wrote the following article. I thought is was very interesting and he gave permission to share it. Andrew Falcon is his pseudonym.
"Why do you tap your oil pressure gauge?
Guest contributor Andrew Falcon
I have seen many motorists with the old analogue gauges give them a tap or two to ensure an accurate reading. However, how many know why it works, because it does work. Nor is it necessary to know why it works, but it is interesting.
A scientist would call the process stochastic resonance, an engineer would record the process as percussive readjustment & a philosopher would say a Buriden’s donkey. So lets start with Buriden’s donkey.
Jean Buriden (a.k.a. Jean De Buriden, Johannes Buridanus – Latin) a priest who lived c.1300 – after 1358. Unlike most of his peers he studied art in Paris rather than theology and remained intellectually independent by remaining a secular priest rather than becoming part of a Religious order. He took over lecturing from William of Okham (a.k.a. William of Occam of Occam’s razor fame). He is famous for his theory of inertia, theory of impetus. He also delved into circular impetus and used this to explain the motion of the planets around the sun. Oops, this idea at this time was bound to upset the church who still believed in a flat earth and were firmly against heliocentricity despite overwhelming evidence. It was the kind of thing that could get you burnt at the stake for heresy. Jean Buriden was sentenced to be tied in a sack and cast into the Seine but was saved by the ingenuity of a student François Villon. Newton used Buriden’s theories as a basis for his laws of mechanics.
But philosophers remember Buriden as the inventor of the thought experiment. Buriden said imagine a donkey, who is thirsty and starving. If the donkey is halfway between water and food it could remain in a state of indecision. What is required is to give the donkey a nudge, the direction is not important, to enable the donkey to find a new state of equilibrium.
Engineers with percussive readjustment. Well that is the polite form, the kind of comment you would put on an invoice to the client. Experience has taught engineers that saying “I hit it with a hammer to fix it” does not help customer relations. Even though it is a legitimate technique.
Scientists and engineers would call it stochastic resonance, particularly if they had studied System Dynamics. A system is said to be stochastic if the outcome is non-deterministic because it has a mixture of the predictable and the unpredictable. The more complex a system the more stochastic the outcome. Which is why when managing a large organisation you should, when issuing a global order, check the result locally. The outcome often follows the law of unintended consequences. In order to gain order most politicians or executives apply more and more control, usually by rules and regulation. This actually causes more disorder. What is needed is the application of a little bit of chaos.
Firstly, the control bit. The best paper on this is “On Governors” in the Proceedings of the Royal Society by James Clark Maxwell in the 1860’s. This paper was about steam engines. Most of you will have seen a governor or controller on a steam engine with two large balls flying in and out to control a throttle. There is a condition called ‘hunting’ where the balls fly in and out in a wild chaotic fashion. It is caused by over-control.
The best demonstration I have seen of this effect is a table vibrating with a single frequency. On the table are ping-pong balls which jump up & down in a chaotic fashion. However when a low intensity random frequency is added to the table the ping-pong balls behave in a neat orderly manner.
Do you remember the old walkie-talkies. There was a squelch knob which introduced a low hiss to the speaker. If one was listening to loads of messages wandering in from the ether you might hear a mayday call which is garbled. By adjusting the squelch knob you could suddenly get clarity on that signal. The squelch knob introduced white noise, a set of random chaotic audio, to produce an enhanced message. This technique is used to '‘clean up'’ audio & video signals. For instance, a GPS signal has the same strength as a car headlamp seen from 20,000 miles away and without techniques like stochastic resonance you would never be able to read it.
In brief, in a nutshell, that is why you tap your oil gauge."
In a sense, the Wave, could be considered like 'taping our gauge' albeit at a 300,00 year interval. Our current extreme earth changes, geo-political upheavals and increasing celestial activity seem like "a little bit of chaos" to me. I must confess to struggling with very detailed scientific matters, although I find it so interesting. Fortunetley, my friend has alot of patience with me :)
_http://en.wikipedia.org/wiki/Stochastic_resonance
Stochastic resonance (SR) is a phenomenon where a signal that is normally too weak to be detected by a sensor, can be boosted by adding white noise to the signal, which contains a wide spectrum of frequencies. The frequencies in the white noise corresponding to the original signal's frequencies will resonate with each other, amplifying the original signal while not amplifying the rest of the white noise (thereby increasing the signal-to-noise ratio which makes the original signal more prominent). Further, the added white noise can be enough to be detectable by the sensor, which can then filter it out to effectively detect the original, previously-undetectable signal.
This phenomenon of boosting undetectable signals by resonating with added white noise extends to many other systems, whether electromagnetic, physical or biological, and is an area of intense research. [1]
Contents [hide]
1 Technical Description
2 Suprathreshold stochastic resonance
3 Neuroscience/psychology and biology
4 Medicine
5 Signal analysis
6 See also
7 References
8 Bibliography
8.1 Bibliography for suprathreshold stochastic resonance
9 External links
Technical Description [edit]Stochastic resonance is observed when noise added to a system changes the system's behaviour in some fashion. More technically, SR occurs if the signal-to-noise ratio of a nonlinear system or device increases for moderate values of noise intensity. It often occurs in bistable systems or in systems with a sensory threshold and when the input signal to the system is "sub-threshold". For lower noise intensities, the signal does not cause the device to cross threshold, so little signal is passed through it. For large noise intensities, the output is dominated by the noise, also leading to a low signal-to-noise ratio. For moderate intensities, the noise allows the signal to reach threshold, but the noise intensity is not so large as to swamp it. Thus, a plot of signal-to-noise ratio as a function of noise intensity shows a '∩' shape.
Strictly speaking, stochastic resonance occurs in bistable systems, when a small periodic (sinusoidal) force is applied together with a large wide band stochastic force (noise). The system response is driven by the combination of the two forces that compete/cooperate to make the system switch between the two stable states. The degree of order is related to the amount of periodic function that it shows in the system response. When the periodic force is chosen small enough in order to not make the system response switch, the presence of a non-negligible noise is required for it to happen. When the noise is small very few switches occur, mainly at random with no significant periodicity in the system response. When the noise is very strong a large number of switches occur for each period of the sinusoid and the system response does not show remarkable periodicity. Between these two conditions, there exists an optimal value of the noise that cooperatively concurs with the periodic forcing in order to make almost exactly one switch per period (a maximum in the signal-to-noise ratio).
Such a favorable condition is quantitatively determined by the matching of two time scales: the period of the sinusoid (the deterministic time scale) and the Kramers rate[citation needed] (i.e., the average switch rate induced by the sole noise: the inverse of the stochastic time scale[2][3]). Thus the term "stochastic resonance".
Stochastic resonance was discovered and proposed for the first time in 1981 to explain the periodic recurrence of ice ages.[4] Since then the same principle has been applied in a wide variety of systems. Nowadays stochastic resonance is commonly invoked when noise and nonlinearity concur to determine an increase of order in the system response.
Suprathreshold stochastic resonance [edit]Suprathreshold stochastic resonance is a particular form of stochastic resonance. It is the phenomenon where random fluctuations, or noise, provide a signal processing benefit in a nonlinear system. Unlike most of the nonlinear systems where stochastic resonance occurs, suprathreshold stochastic resonance occurs not only when the strength of the fluctuations is small relative to that of an input signal, but occurs even for the smallest amount of random noise. Furthermore, it is not restricted to a subthreshold signal, hence the qualifier.
Neuroscience/psychology and biology [edit]Main article: Stochastic resonance (sensory neurobiology)
Stochastic resonance has been observed in the neural tissue of the sensory systems of several organisms.[5] Computationally, neurons exhibit SR because of non-linearities in their processing. SR has yet to be fully explained in biological systems, but neural synchrony in the brain (specifically in the gamma wave frequency[6]) has been suggested as a possible neural mechanism for SR by researchers who have investigated the perception of "subconscious" visual sensation.[7]
Medicine [edit]SR-based techniques have been used to create a novel class of medical devices for enhancing sensory and motor functions such as vibrating insoles especially for the elderly, or patients with diabetic neuropathy or stroke.
See the Review of Modern Physics[8] article for a comprehensive overview of stochastic resonance.
Signal analysis [edit]A related phenomenon is dithering applied to analog signals before analog-to-digital conversion.[9] Stochastic resonance can be used to measure transmittance amplitudes below an instrument's detection limit. If Gaussian noise is added to a subthreshold (i.e., immeasurable) signal, then it can be brought into a detectable region. After detection, the noise is removed. A fourfold improvement in the detection limit can be obtained.[10]
"Why do you tap your oil pressure gauge?
Guest contributor Andrew Falcon
I have seen many motorists with the old analogue gauges give them a tap or two to ensure an accurate reading. However, how many know why it works, because it does work. Nor is it necessary to know why it works, but it is interesting.
A scientist would call the process stochastic resonance, an engineer would record the process as percussive readjustment & a philosopher would say a Buriden’s donkey. So lets start with Buriden’s donkey.
Jean Buriden (a.k.a. Jean De Buriden, Johannes Buridanus – Latin) a priest who lived c.1300 – after 1358. Unlike most of his peers he studied art in Paris rather than theology and remained intellectually independent by remaining a secular priest rather than becoming part of a Religious order. He took over lecturing from William of Okham (a.k.a. William of Occam of Occam’s razor fame). He is famous for his theory of inertia, theory of impetus. He also delved into circular impetus and used this to explain the motion of the planets around the sun. Oops, this idea at this time was bound to upset the church who still believed in a flat earth and were firmly against heliocentricity despite overwhelming evidence. It was the kind of thing that could get you burnt at the stake for heresy. Jean Buriden was sentenced to be tied in a sack and cast into the Seine but was saved by the ingenuity of a student François Villon. Newton used Buriden’s theories as a basis for his laws of mechanics.
But philosophers remember Buriden as the inventor of the thought experiment. Buriden said imagine a donkey, who is thirsty and starving. If the donkey is halfway between water and food it could remain in a state of indecision. What is required is to give the donkey a nudge, the direction is not important, to enable the donkey to find a new state of equilibrium.
Engineers with percussive readjustment. Well that is the polite form, the kind of comment you would put on an invoice to the client. Experience has taught engineers that saying “I hit it with a hammer to fix it” does not help customer relations. Even though it is a legitimate technique.
Scientists and engineers would call it stochastic resonance, particularly if they had studied System Dynamics. A system is said to be stochastic if the outcome is non-deterministic because it has a mixture of the predictable and the unpredictable. The more complex a system the more stochastic the outcome. Which is why when managing a large organisation you should, when issuing a global order, check the result locally. The outcome often follows the law of unintended consequences. In order to gain order most politicians or executives apply more and more control, usually by rules and regulation. This actually causes more disorder. What is needed is the application of a little bit of chaos.
Firstly, the control bit. The best paper on this is “On Governors” in the Proceedings of the Royal Society by James Clark Maxwell in the 1860’s. This paper was about steam engines. Most of you will have seen a governor or controller on a steam engine with two large balls flying in and out to control a throttle. There is a condition called ‘hunting’ where the balls fly in and out in a wild chaotic fashion. It is caused by over-control.
The best demonstration I have seen of this effect is a table vibrating with a single frequency. On the table are ping-pong balls which jump up & down in a chaotic fashion. However when a low intensity random frequency is added to the table the ping-pong balls behave in a neat orderly manner.
Do you remember the old walkie-talkies. There was a squelch knob which introduced a low hiss to the speaker. If one was listening to loads of messages wandering in from the ether you might hear a mayday call which is garbled. By adjusting the squelch knob you could suddenly get clarity on that signal. The squelch knob introduced white noise, a set of random chaotic audio, to produce an enhanced message. This technique is used to '‘clean up'’ audio & video signals. For instance, a GPS signal has the same strength as a car headlamp seen from 20,000 miles away and without techniques like stochastic resonance you would never be able to read it.
In brief, in a nutshell, that is why you tap your oil gauge."
In a sense, the Wave, could be considered like 'taping our gauge' albeit at a 300,00 year interval. Our current extreme earth changes, geo-political upheavals and increasing celestial activity seem like "a little bit of chaos" to me. I must confess to struggling with very detailed scientific matters, although I find it so interesting. Fortunetley, my friend has alot of patience with me :)
_http://en.wikipedia.org/wiki/Stochastic_resonance
Stochastic resonance (SR) is a phenomenon where a signal that is normally too weak to be detected by a sensor, can be boosted by adding white noise to the signal, which contains a wide spectrum of frequencies. The frequencies in the white noise corresponding to the original signal's frequencies will resonate with each other, amplifying the original signal while not amplifying the rest of the white noise (thereby increasing the signal-to-noise ratio which makes the original signal more prominent). Further, the added white noise can be enough to be detectable by the sensor, which can then filter it out to effectively detect the original, previously-undetectable signal.
This phenomenon of boosting undetectable signals by resonating with added white noise extends to many other systems, whether electromagnetic, physical or biological, and is an area of intense research. [1]
Contents [hide]
1 Technical Description
2 Suprathreshold stochastic resonance
3 Neuroscience/psychology and biology
4 Medicine
5 Signal analysis
6 See also
7 References
8 Bibliography
8.1 Bibliography for suprathreshold stochastic resonance
9 External links
Technical Description [edit]Stochastic resonance is observed when noise added to a system changes the system's behaviour in some fashion. More technically, SR occurs if the signal-to-noise ratio of a nonlinear system or device increases for moderate values of noise intensity. It often occurs in bistable systems or in systems with a sensory threshold and when the input signal to the system is "sub-threshold". For lower noise intensities, the signal does not cause the device to cross threshold, so little signal is passed through it. For large noise intensities, the output is dominated by the noise, also leading to a low signal-to-noise ratio. For moderate intensities, the noise allows the signal to reach threshold, but the noise intensity is not so large as to swamp it. Thus, a plot of signal-to-noise ratio as a function of noise intensity shows a '∩' shape.
Strictly speaking, stochastic resonance occurs in bistable systems, when a small periodic (sinusoidal) force is applied together with a large wide band stochastic force (noise). The system response is driven by the combination of the two forces that compete/cooperate to make the system switch between the two stable states. The degree of order is related to the amount of periodic function that it shows in the system response. When the periodic force is chosen small enough in order to not make the system response switch, the presence of a non-negligible noise is required for it to happen. When the noise is small very few switches occur, mainly at random with no significant periodicity in the system response. When the noise is very strong a large number of switches occur for each period of the sinusoid and the system response does not show remarkable periodicity. Between these two conditions, there exists an optimal value of the noise that cooperatively concurs with the periodic forcing in order to make almost exactly one switch per period (a maximum in the signal-to-noise ratio).
Such a favorable condition is quantitatively determined by the matching of two time scales: the period of the sinusoid (the deterministic time scale) and the Kramers rate[citation needed] (i.e., the average switch rate induced by the sole noise: the inverse of the stochastic time scale[2][3]). Thus the term "stochastic resonance".
Stochastic resonance was discovered and proposed for the first time in 1981 to explain the periodic recurrence of ice ages.[4] Since then the same principle has been applied in a wide variety of systems. Nowadays stochastic resonance is commonly invoked when noise and nonlinearity concur to determine an increase of order in the system response.
Suprathreshold stochastic resonance [edit]Suprathreshold stochastic resonance is a particular form of stochastic resonance. It is the phenomenon where random fluctuations, or noise, provide a signal processing benefit in a nonlinear system. Unlike most of the nonlinear systems where stochastic resonance occurs, suprathreshold stochastic resonance occurs not only when the strength of the fluctuations is small relative to that of an input signal, but occurs even for the smallest amount of random noise. Furthermore, it is not restricted to a subthreshold signal, hence the qualifier.
Neuroscience/psychology and biology [edit]Main article: Stochastic resonance (sensory neurobiology)
Stochastic resonance has been observed in the neural tissue of the sensory systems of several organisms.[5] Computationally, neurons exhibit SR because of non-linearities in their processing. SR has yet to be fully explained in biological systems, but neural synchrony in the brain (specifically in the gamma wave frequency[6]) has been suggested as a possible neural mechanism for SR by researchers who have investigated the perception of "subconscious" visual sensation.[7]
Medicine [edit]SR-based techniques have been used to create a novel class of medical devices for enhancing sensory and motor functions such as vibrating insoles especially for the elderly, or patients with diabetic neuropathy or stroke.
See the Review of Modern Physics[8] article for a comprehensive overview of stochastic resonance.
Signal analysis [edit]A related phenomenon is dithering applied to analog signals before analog-to-digital conversion.[9] Stochastic resonance can be used to measure transmittance amplitudes below an instrument's detection limit. If Gaussian noise is added to a subthreshold (i.e., immeasurable) signal, then it can be brought into a detectable region. After detection, the noise is removed. A fourfold improvement in the detection limit can be obtained.[10]
