The Soporific Sound of Settled Science

The Soporific Sound of Settled Science

Like many other Baby Boomers I have fond childhood memories of being enveloped by swirling clouds of sulphurous smoke whenever an express train roared through the station on its way to more important [and exciting] places.

In those far off days I commuted to school by electric train with my elder brother who was a keen train spotter with a fine appreciation for engineering, a keen eye for the sleek lines of Mallard and a wondrous rapture for the ever elusive Deltic.

Mallard and Deltic

My appreciation was more prosaic because I just enjoyed being engulfed in smoke as the Pullman from Portsmouth hurtled by on its way to the bright lights of London.

Consequently, with years of experience listening to steam trains, it was an easy sell for my Physics master when the time arrived [one sunny, soporific afternoon in school] to teach me about the Doppler Effect.

The Doppler effect (or Doppler shift) is the change in frequency of a wave (or other periodic event) for an observer moving relative to its source.

It is named after the Austrian physicist Christian Doppler, who proposed it in 1842 in Prague.

It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from an observer.

Compared to the emitted frequency, the received frequency is higher during the approach, identical at the instant of passing by, and lower during the recession.

https://en.wikipedia.org/wiki/Doppler_effect

Train whistle and Doppler Effect

Conversely, because everyone knows all about the Doppler Effect, it’s a very difficult topic to approach critically because it challenges so many deeply ingrained beliefs.

Nonetheless, [for those interested in the Settled Science of Light, Red Shift and Big Bang] it is important to recognize that what you understand to be the Doppler Effect is not the full story.

In fact, the subtlety of the subterfuge surrounding the Doppler Effect is simply staggering.

So take a deep breath and read on.

The subtlety of the Doppler Effect subterfuge relies upon teaching a plausible theory that doesn’t actually explain away all of the observational information that is presented.

The Doppler Effect is a classic case of misdirection by omission.

Any budding Poirot should pause at this point to search for clues in the steam train video [above] and the referenced Wikipedia entry for the Doppler Effect.

Hercule Poirot

The really important observational information is contained in the soundtrack of the train video.

Acela express kicking up piles of snow

The sound of the approaching train gets continuously louder as it approaches and the pitch of the sounds increases continuously as the train approaches.

The sound of the receding train gets continuously quieter as it recedes and the pitch of the sounds decreases continuously as the train recedes.

The first point to note is that the continuously changing loudness is not covered by the Doppler Effect and [strangely enough] was completely ignored by my Physics teacher.

However, let’s place the issue of loudness on the back burner for the moment.

The second point to note is that the continuously changing pitch [also] is not covered by the Doppler Effect.

The pivotal point is that the Doppler Effect is a one time change in frequency [for an approaching/receding train at a constant speed] i.e. a one time Doppler Shift.

The Doppler Effect (or Doppler Shift) is the change in frequency of a wave (or other periodic event) for an observer moving relative to its source.

Compared to the emitted frequency, the received frequency is higher during the approach, identical at the instant of passing by, and lower during the recession.

Doppler Formula

https://en.wikipedia.org/wiki/Doppler_effect

sound_doppler_effect

Doppler Effect for Sound – Ron Kurtus – Revised 6 November 2012
Ron Kurtus’ School for Champions
http://www.school-for-champions.com/science/sound_doppler_effect.htm

This one time Doppler Shift in frequency is clearly illustrated when the mainstream is discussing [for example] Pulse-Doppler Radar or Red Shift.

Doppler_effect_diagrammatic

http://en.wikipedia.org/wiki/Pulse-Doppler_radar

Red Shift

The Doppler effect for electromagnetic waves such as light is of great use in astronomy and results in either a so-called redshift or blueshift.

https://en.wikipedia.org/wiki/Doppler_effect

CalcTool.org provides a superb online Doppler Shift calculator which shows [for example] that a sound emitted at 261.6 Hz [C4 – Middle C] by a source travelling away from the observer at a speed of 100 kilometres per hour [27.78 m/s] will be perceived by the observer to be at 242 Hz.

Calctool.org - Doppler Shift

CalcTool.org – Doppler Shift – Andy & Steve Shipway – 2008
http://www.calctool.org/CALC/phys/default/doppler

The above Doppler Shift example [with the source travelling away from the observer at 100 kph] is roughly equivalent to just one key [lower to B3 246.9 Hz] on a piano keyboard.

See: https://en.wikipedia.org/wiki/Piano_key_frequencies

In other words:
The actual pitch change attributable to the Doppler Effect in the train videos is very trivial.

Furthermore, because a train produces a complex combination of sound frequencies across the sound spectrum it is unlikely that this one time Doppler Shift of about 7.5% in the entire sound spectrum produced by a moving train would be noticeable to the untrained ear.

Evidently something else is responsible for the observed continuously changing pitch.

The first step to understanding this something else is the logarithmic Decibel.

The decibel (dB) is a logarithmic unit used to express the ratio between two values of a physical quantity, often power or intensity.

One of these quantities is often a reference value, and in this case the decibel can be used to express the absolute level of the physical quantity, as in the case of sound pressure.

The number of decibels is ten times the logarithm to base 10 of the ratio of two power quantities, or of the ratio of the squares of two field amplitude quantities.

One decibel is one tenth of one bel, named in honor of Alexander Graham Bell.

The bel is seldom used without the deci- prefix.

Decibel

In acoustics the reference pressure used to define the Decibel “is set at the typical threshold of perception of an average human”.

The decibel is commonly used in acoustics as a unit of sound pressure level.

The reference pressure in air is set at the typical threshold of perception of an average human and there are common comparisons used to illustrate different levels of sound pressure.

The human ear has a large dynamic range in audio reception.

The ratio of the sound intensity that causes permanent damage during short exposure to the quietest sound that the ear can hear is greater than or equal to 1 trillion (1012).

Such large measurement ranges are conveniently expressed in logarithmic scale: the base-10 logarithm of 1012 is 12, which is expressed as a sound pressure level of 120 dB re 20 micropascals.

https://en.wikipedia.org/wiki/Decibel

The human range is commonly given as 20 to 20,000 Hz, though there is considerable variation between individuals, especially at high frequencies, and a gradual decline with age is considered normal.

https://en.wikipedia.org/wiki/Hearing_range

A human is capable of hearing (and usefully discerning) anything from a quiet murmur in a soundproofed room to the sound of the loudest heavy metal concert.

Such a difference can exceed 100 dB which represents a factor of 100,000 in amplitude and a factor 10,000,000,000 in power.

https://en.wikipedia.org/wiki/Dynamic_range

Accordingly, the very loud noise associated with being “close to a train” is rated at 110 Decibels.

Decibel Examples

See: http://home.earthlink.net/~dnitzer/4HaasEaton/Decibel.html
See: https://en.wikipedia.org/wiki/Sound_pressure#Examples_of_sound_pressure

The next step is to appreciate that the continuously changing loudness [Decibels] perceived in the train videos [above] is partly caused by Sound Divergence whereby the intensity of a sound wave dissipates [according to the Inverse Square Law] as it radiates away from the source.

When sound spreads out evenly in all directions in three dimensions, the intensity drops in proportion to the inverse square of the distance.

https://en.wikipedia.org/wiki/Speed_of_sound#Gradients

In physics, an inverse-square law is any physical law stating that a specified physical quantity or intensity is inversely proportional to the square of the distance from the source of that physical quantity.

Inverse-square law

https://en.wikipedia.org/wiki/Inverse-square_law

The next step is to appreciate that the continuously changing loudness [Decibels] in the train videos [above] is also partly caused by Acoustic Attenuation [aka Sound Absorption].

Acoustic attenuation is a measure of the energy loss of sound propagation in media.

Most media have viscosity, and are therefore not ideal media.

When sound propagates in such media, there is always thermal consumption of energy caused by viscosity.

For inhomogeneous media, besides media viscosity, acoustic scattering is another main reason for removal of acoustic energy.

https://en.wikipedia.org/wiki/Acoustic_attenuation

These mysteries of sound propagation were beautifully explained by Dennis Bohn back in 1988.

Sound propagates through air as a wave in an elastic medium.

Since air is not a perfectly elastic medium, this pulsating action causes several complex irreversible processes to occur.

The wave action of air causes minute turbulence of the air molecules through which it passes.

Each affected molecule robs the wave of some of its energy until eventually the wave dies completely.

If this were not so, every sound generated would travel forever and we would live within a sonic shell of cacophony.

Absorption works with divergence.

Divergence of sound causes a reduction in the sound intensity due to spreading of the wave throughout the medium.

The sound pressure level will decrease 6 dB for each doubling of the distance, that is, it is inversely proportional to the square of the distance.

This well-known fact occurs simultaneously with absorption.

Absorption describes the energy-exchanging mechanism occurring during divergence.

So not only is the wave spreading, it is also dying.

Environmental Effects on the Speed of Sound
Dennis A. Bohn – Rane Corporation, Mukilteo, WA 98275 USA
J. Audio Eng. Soc. – Vol. 36, No. 4 – 1988 April
http://www.rane.com/pdf/eespeed.pdf

The wonder and excitement experienced by Dennis Bohn is palpable as he explains the arcane complexities of sound attenuation which is dependent upon temperature, humidity and [most important of all in this context] frequency.

The strict confines of the ideal fluid-dynamic equations cannot explain the attenuation of sound.

Theoretical predictions must include bulk viscosity, thermal conduction, and molecular relaxation for agreement with measured results.

Conservation of mass, entropy for the gas, and molecular vibrations all enter into the thermodynamic equilibrium equations.

To truly understand all the mechanisms of sound absorption in air, the interested reader must be ready to study molecular kinetics, vibrational relaxation processes, and Navier-Stokes equations, and must know what a Laplacian is.

Complete linear acoustic equations are not for the fainthearted.

The mathematically courageous should refer to Pierce, where a painstakingly rigorous presentation is available.

Fortunately a simplified, yet accurate, alternate path exists.

All of the above effects will combine into a term labeled total attenuation coefficient and designated by the letter m.

This term is frequency, temperature, and humidity dependent.

Environmental Effects on the Speed of Sound
Dennis A. Bohn – Rane Corporation, Mukilteo, WA 98275 USA
J. Audio Eng. Soc. – Vol. 36, No. 4 – 1988 April
http://www.rane.com/pdf/eespeed.pdf

Now we are in a position to appreciate that the continuously changing pitch in the train videos [above] is caused by the attenuation of high frequency sounds.

Sound Attenuation

Environmental Effects on the Speed of Sound
Dennis A. Bohn – Rane Corporation, Mukilteo, WA 98275 USA
J. Audio Eng. Soc. – Vol. 36, No. 4 – 1988 April
http://www.rane.com/pdf/eespeed.pdf

The CRC Handbook of Chemistry and Physics tabulates the attenuation of sound in units of Decibels per Kilometres.

Attenuation and Speed of Sound in Air
Attenuation and Speed of Sound in Air as a Function of Humidity and Frequency
All values refer to still air at 20 C.
The CRC Handbook of Chemistry and Physics

Therefore, in the train videos [above]:

1) As the train approaches the observer the high frequency sounds experience progressively less attenuation [as the distance decreases] and the perceived pitch increases.

2) As the train recedes from the observer the high frequency sounds experience progressively more attenuation [as the distance increases] and the perceived pitch decreases.

Attenuation Graph

Thus the fluctuating pitch has nothing to do with the Doppler Effect and everything to do with attenuation of high frequency sound waves.

The attenuation of high frequency sounds was well understood by Robert Foulis when he invented “first automated steam-powered foghorn” which produced low frequency sound.

The first automated steam-powered foghorn was invented by Robert Foulis, a Scotsman who emigrated to Saint John, New Brunswick, Canada.

Foulis is said to have heard his daughter playing the piano in the distance on a foggy night, and noticed the low notes were more audible than the higher notes: he then designed a device to produce a low-frequency sound, as well as a code system for use with it.

Foghorn

http://en.wikipedia.org/wiki/Foghorn

This obviously leads to the question:

What is the motivation behind this bizarre Doppler Effect charade?

The answer to that question requires further research.

But, so far, I have stumbled upon two clues.

Firstly, the speed of sound is frequency dependent.

The speed of sound in an ideal gas is independent of frequency, but does vary slightly with frequency in a real gas.

https://en.wikipedia.org/wiki/Speed_of_sound

Speed of Sound in Air Graph

Therefore, contrary to the Settled Science, it’s possible that the Speed of Light is frequency dependent especially as interstellar space is not a vacuum.

The speed of light in vacuum, commonly denoted c, is a universal physical constant important in many areas of physics.

Its value is exactly 299,792,458 metres per second (≈3.00×108 m/s), as the length of the metre is defined from this constant and the international standard for time.

https://en.wikipedia.org/wiki/Speed_of_light

Interstellar space is the physical space within a galaxy beyond the influence of each star on the plasma.

The contents of interstellar space are called the interstellar medium.

Approximately 70% of the mass of the interstellar medium consists of lone hydrogen atoms; most of the remainder consists of helium atoms.

The density of matter in the interstellar medium can vary considerably: the average is around 106 particles per m3, but cold molecular clouds can hold 108–1012 per m3.

http://en.wikipedia.org/wiki/Outer_space#Interstellar_space

The second clue comes from the spectrum of Sirius [dated 1888] which suggests high frequency light may be subject to attenuation in interstellar space.

Spectra of the Sun and Sirius

The spectroscope and its work – Richard A Proctor – 1888
Society for Promoting Christian Knowledge
https://archive.org/details/spectroscopeitsw00procrich

If light is subject to high frequency attenuation then the Tortured Science held captive by the medieval barons of Astronomy may yet be set free.

Radio galaxies and their relatives, radio-loud quasars and blazars, are types of active galaxy that are very luminous at radio wavelengths, with luminosities up to 1039 W between 10 MHz and 100 GHz.

https://en.wikipedia.org/wiki/Radio_galaxy

In physics, redshift happens when light or other electromagnetic radiation from an object is increased in wavelength, or shifted to the red end of the spectrum.

In general, whether or not the radiation is within the visible spectrum, “redder” means an increase in wavelength – equivalent to a lower frequency and a lower photon energy, in accordance with, respectively, the wave and quantum theories of light.

Some redshifts are an example of the Doppler effect, familiar in the change in the apparent pitches of sirens and frequency of the sound waves emitted by speeding vehicles.

A redshift occurs whenever a light source moves away from an observer.

Another kind of redshift is cosmological redshift, which is due to the expansion of the universe, and sufficiently distant light sources (generally more than a few million light years away) show redshift corresponding to the rate of increase in their distance from Earth.

Subsequently, Edwin Hubble discovered an approximate relationship between the redshifts of such “nebulae” and the distances to them with the formulation of his eponymous Hubble’s law.

These observations corroborated Alexander Friedmann’s 1922 work, in which he derived the famous Friedmann equations.

They are today considered strong evidence for an expanding universe and the Big Bang theory.

https://en.wikipedia.org/wiki/Redshift

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3 Responses to The Soporific Sound of Settled Science

  1. Brian H says:

    I hear expansion is out again. Don’t know if there’s consensus, though. ;p

  2. oldbrew says:

    Speed of sound / temperature / viscosity seem closely related in our world.
    http://www.digitaldutch.com/atmoscalc/graphs.htm

  3. malagabay says:

    A very timely master class on Attenuation given by Mike Adams.

    In essence, because of the differences in the speed of sound vs. the speed of the bullets from a known cartridge (.223 Remington, in this case), the time lag between the last bullet hitting the pavement and the last audible report of the rifle muzzle can be used to very accurately calculate the range of the shooter.

    More importantly, when the audio from the Las Vegas shooting is analyzed, it reveals TWO shooters operating at the same time, not just one shooter. Shooter #1 is operating at 425 – 475 yards, which is consistent with the Mandalay Bay hotel, but shooter #2 is operating at approximately 250 – 270 yards.

    Forensic acoustic proof of SECOND shooter in the Las Vegas massacre
    Mike Adams – The Health Ranger – Oct 9, 2017

    English (auto-generated) Transcript

    04:41 keep following along here please
    04:44 now I want you to notice these Peaks
    04:46 here that see these five Peaks these are
    04:49 the sound waveforms that represent the
    04:51 sounds of bullets striking the pavement
    04:53 and these are high frequency sounds if
    04:55 you listen to all the audio recordings
    04:57 that you’ll see that these sound high
    04:59 frequency they have a lot of high
    05:01 frequency sound waves in them these on
    05:04 the other hand these are the sound waves
    05:05 of the reports from the rifle in the
    05:08 distance arriving after the bullets have
    05:10 arrived these reports have a lower
    05:13 frequency sound that’s what these notes
    05:15 are about high frequency sound spectra
    05:18 associated with the pavement hits low
    05:21 frequency sound spectra associated with
    05:23 the rifle reports from the distance in
    05:25 other words the gunshot sounds from the
    05:28 distance now why is there a difference
    05:30 in the frequency of the sound spectrum
    05:31 between these two types of sounds the
    05:34 answer has to do with the transmission
    05:37 of sound frequencies through the medium
    05:40 of air and as this chart shows frequency
    05:43 versus sound transmission is an inverse
    05:45 relationship so the lower your frequency
    05:49 in other words low dull sounds have very
    05:51 high transmission over long distances
    05:53 because obviously they involve longer
    05:55 wavelengths on the other hand high
    05:58 frequency sounds such as high pitch
    06:00 sounds or multiple harmonics of sounds
    06:03 have very low transmission through air
    06:05 why is that because they involve very
    06:07 small wavelengths small wavelengths
    06:10 suffer what’s called attenuation during
    06:12 transmission which means they get
    06:13 silenced or you know sort of muzzled or
    06:18 buffered or killed off or whatever you
    06:19 want to say they get reduced as it
    06:23 travels through the air and this is why
    06:25 if you hear gunshots in the distance
    06:27 they are always low thumping sounds
    06:29 they’re not high frequency sounds in
    06:31 fact soldiers throughout the Vietnam War
    06:33 and World War one and two and even
    06:35 modern warfare they know that you can
    06:38 kind of gauge the distance of gunfire
    06:40 based on the frequency…

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