Yes -- quite correct in the number of cycles correlates with energy loss. If there is any "viscosity" --i.e. conversion of motion into heat energy through friction losses -- the loss per wavelength should be constant. In addition, if there are any scattering centers smaller than a wavelength, Rayleigh scattering increases as frequency to the fourth power...

As suggested by David, there are many propagation decay mechanisms which all contribute to the relation between (larger) wavelengths and (longer) distance propagation. But they are physically very distinct hence must be be clearly distinguished - in particular the law of decay versus distance is alternatively linear, squared, exponential... By increased complexity/veracity, you have to consider:

1st step: "Waves" are determined in "perfect continuous media" as a singular solution of the propagation equation (electromagnetic, acoustic...) satisfying the energy conservation law: the cause of decay with distance is only related to the spreading model. At high frequency the dominant model (except for interface waves) is 3D propagation as the medium dimensions in all directions are very large versus wavelength lambda. This turns as 1/r2 level decay. But at lower frequencies media such oceans or earth crust are no more thick enough and long distance propagation is more 2D meaning 1/r level decay - the same for interface waves (Rayleigh...)

2nd step: "perfect media" do not always exist and you have to consider that a fraction of the wave energy turns into heat due to some viscosity/hysteresis of the force/displacement or strain/stress cycles. In an isotropic medium, this is expressed as a loss factor applying from a wavelength to the next L(i+1)=L(i)x(1-èta) adding to the spreading decay. It turns as an exponential decay versus distance (1-èta)power (d/lambda)

3d step: additional losses can occur in some media, as for example molecular absorption for some acoustic wavelengths in sea water; or, in crystals, imperfections alter/scatter the propagation of electrons; or the medium is fractured etc. etc. As a consequence, the propagation model complexity increases with such knowledge of specific physical bias against energy conservation of waves. (scattering is not opposing to energy conservation but to continuous propagation)

All these "losses" are globally increasing/cumulating with the number of wavelengths propagated, which turn into distances inversely proportional to the frequency.

Dear David Vilkomerson,

As a result of the experiments, it was found that the propagation distance of an acoustic wave with a frequency of 80 Hz (wavelength 19 m) is approximately 130 km (wave No. 1), and for a wave with a frequency of 240 Hz (wavelength 6.4 m) is approximately 40 km (wave No. 2). The first and second waves initially have the same power. Before complete loss of propagation transmission, the first and second waves go through approximately the same number of cycles (periods). In fact, the loss of transmission of one cycle of the first wave consumes the same amount of energy as the cycle of the second wave. You wrote: “Yes -- quite correct in the number of cycles correlates with energy loss. If there is any "viscosity" --i.e. conversion of motion into heat energy through friction losses -- the loss per wavelength should be constant.". I did the calculations. As a result of the calculations (http://www.tsuchiya2.org/index_eng.html), it turns out that the total transmission loss of the propagation of wave # 1 before complete attenuation is 0.095 dB, and the second wave is 0.032 dB. This means that the propagation transmission loss per cycle is theoretically assumed to be substantially larger for the first wave than for the second wave. I see this as a contradiction with your statement. How can you explain it?

Sincerely, Boris Kapochkin.

Dear Borys,

As you are dealing with long distance acoustic transmission, you cannot consider it as a propagation in an homogeneous medium...

The atmosphere is much thinner than the propagation range you are looking for, highly stratified (temperature and density), with varying humidity content and wind-induced vortices etc.: how dare would it rightly match with an ideal attenuation law applicable to waves in ideal media of constant properties?

Your observation has a single straightforward conclusion: you CANNOT explain the attenuation only by factoring the air viscosity! It is just not a legitimate physical reasoning...

In particular, if you reason in "rays", the two sound waves at different frequencies will not travel exactly though the same path; the sound speed varies all along the paths (in particular with altitude https://www.fighter-planes.com/jetmach1.htm) hence the wavelength etc. etc. so even your conversion of distance in terms of number of cycles is disputable.

To model the long distance sound attenuation, you have to build a complex model of the atmosphere stratification, and use a multiple rays propagation algorithm with various perturbations to factor variations of humidity and rain patches, turbulences etc. (and, over hilly or mountainous land masses, also introduce a 3D terrain model)... Humidity is very influential on sound absorption at low frequencies, almost in a 1 to 10 ratio at 80Hz - see for example https://www.engineeringtoolbox.com/air-speed-sound-attenuation-humidity-frequency-d_2161.html.

In physical terms, you might state in short that this complexity relate to the fact that Rayleigh diffusion law (which rules acoustics) is not easy to combine with Navier Stokes (which rules the atmospheric medium heterogeneity) when trying to establish the propagation model... And actual humidity levels along the acoustic paths are probably the dominant factor to take into account, so you need to incorporate radar meteorological data if you collect field data.

A good workplan for the New Year!

Dear Bernard Garnier,

Your quote: "As you are dealing with long distance acoustic transmission, you cannot consider it as a propagation in an homogeneous medium...". I My calculations are correct since I made the comparison for two frequencies but under the same conditions. If you can refute my calculations, then do it correctly.

Your quote: "The atmosphere is much thinner than the propagation range you are looking for, highly stratified (temperature and density), with varying humidity content and wind-induced vortices etc.: how dare it rightly match with an ideal attenuation law applicable to waves in ideal media of constant properties? Your observation has a single straightforward conclusion: you CANNOT explain the attenuation only by factoring the air viscosity! It is just not a legitimate physical reasoning...".

Your quote: "To model the long distance sound attenuation, you have to build a complex model of the atmosphere stratification, and use a multiple rays propagation algorithm with various perturbations to factor variations of humidity and rain patches, turbulences etc. (and, over hilly or mountainous land masses, also introduce a 3D terrain model)... Humidity is very influential on sound absorption at low frequencies, almost in a 1 to 10 ratio at 80Hz - see for example https://www.engineeringtoolbox.com/air-speed-sound-attenuation-humidity-frequency-d_2161.html.

In physical terms, you might state in short that this complexity relate to the fact that Rayleigh diffusion law (which rules acoustics) is not easy to combine with Navier Stokes (which rules the atmospheric medium heterogeneity) when trying to establish the propagation model... And actual humidity levels along the acoustic paths are probably the dominant factor to take into account, so you need to incorporate radar meteorological data if you collect field data.".

Read the discussion topic carefully. Here the problem of the atmosphere is not yet considered by me.

Dear Bernard Garnier, Your quote: "In particular, if you reason in "rays", the two sound waves at different frequencies will not travel exactly though the same path; the sound speed varies all along the paths (in particular with altitude https://www. fighter-planes.com/jetmach1.htm) hence the wavelength etc. etc. so even your conversion of distance in terms of number of cycles is disputable.". Read the discussion topic carefully. Firstly, here the problem of refraction is not yet considered by me. Secondly, you badly taught physics. Thirdly, your doubt that for waves with different frequencies complete attenuation occurs after the passage of the same number of cycles is not confirmed by anything. At what here a refraction I did not understand. I think no one understands you. The opinion expressed must be argued otherwise it is empty words.

Sincerely, Boris.

Dear Borys Kapochkin

The excellent discussion of the problem is provided in the Physics Stack Exchange (the answer with the highest number of upvotes):

https://physics.stackexchange.com/questions/87751/do-low-frequency-sounds-really-carry-longer-distances

For the extreme case of low frequency acoustic waves we can consider the waves generated by volcanic eruptions. The “music“ from these sources can travel very well around the entire planet and it is used effectively to monitor the active volcanoes.

https://eos.org/science-updates/monitoring-volcanic-craters-with-infrasound-music

My best wishes for the New Year,

Janusz

Dear Borys,

I am surprised by the vehemence of your argumentation. I have worked in the past on long distance propagation of artillery noise and helicopter rotor noise, and my observations are not fictitious at all...

Effectively if you recorded your 2 sound waves in the same time and positions (what you was not stating originally) you get a number of factors out at least for a first order assessment, however even if your two waves followed exactly the same path, which is probably not true, the large difference of absorption by humidity between 240 and 80Hz is just in itself largely sufficient to justify a much stronger decay per wavelength of your lowest frequency sound - just have a look on the curves spread (noting they are expressed in dB/km, so the spread in dB per wavelength is far larger). And this absorption is not the only frequency-dependent factor of the equations...

Have a good day, and please remain humble when facing the complexity of real acoustics,

Bernard

Dear Bernard Garnier. Once again, I want to clarify my argument. A question was asked about the physics of the maximum propagation range of mechanical waves of different frequencies. In the topic of the discussion, I made a postulate: "Long mechanical waves in all physical media propagate farther than short ones. This is a general law." This postulate has not yet been questioned by anyone. In the topic of the discussion, I asked the question: "What is the physics of this phenomenon?" Look at the first sentence of the discussion - "Yes - quite correct in the number of cycles correlates with energy loss." I did not agree that the existing theory recognizes this fact. I chose two waves with different frequencies and calculated the sound propagation loss in water for the maximum range using a hydroacoustic calculator (http://www.tsuchiya2.org/index_eng.html). The actual propagation ranges of the selected waves were assigned. What happened. Based on the existing theory of sound attenuation in water, which is applied in (http://www.tsuchiya2.org/index_eng.html), it turned out that one cycle of a wave with a frequency of 80 Hz during propagation spends less energy than one cycle of a wave with a frequency of 240 Hz. With this, I questioned the first phrase of the discussion "Yes - quite correct in the number of cycles correlates with energy loss.". I think it's clear now? If you do not agree with my postulate: "Long mechanical waves in all physical media propagate farther than short ones. This is a general law", please argue. If you agree with the postulate and know the answer to my question "What is the physics of this phenomenon?", write the answer. You write "please remain humble when facing the complexity of real acoustics.". I adhere to the position that there is nothing complicated in science. In science, everything is simple if there is an understanding of the process. Sincerely, Boris Kapochkin.

Dear Borys,

Please just understand that, in absolute, in the physical word we share, your statement is wrong! You might say "in most cases long mechanical waves propagate farther than shorter ones" but you can find in many media (real acoustic fluids, crystals etc) specific counter-examples where longer mechanical waves are absorbed or diffracted much faster than shorter ones and do not propagate as far...

Dear Bernard Garnier. You do not agree with my postulate: "Long mechanical waves in all physical media propagate farther than short ones. This is a general law". The argument is very vague. It is necessary to give specific examples. Then there will be a subject for discussion. Based on your logic, the law of physics F=m*a and all other laws of physics are not universal? Sincerely, Boris Kapochkin.

Howdy Borys Kapochkin,

We are certainly being made aware of the range of acoustic phenomena, here and in another discussion. Mostly valid stuff; seldom appropriate here. I also would like a more specific reply discussing your postulate and question. The issue that seems to be missed in earlier replies is that you are exploring, seeking a deeper understanding and explanation of natural process. Your data suggest an interpretation, ? is it valid ?.

I affirm the view you have expressed in an answer: "I adhere to the position that there is nothing complicated in science. In science, everything is simple if there is an understanding of the process." Half-knowing use of interim results is a different matter - very difficult - needs humility. In Charles Ives musical work "The Unanswered Question," the exploring trumpet has the last word against the knowing woodwinds while the strings drone on with "the music of the spheres." Keep exploring!

Happy Trails, Len

Dear Borys,

As you know a single counter-example is enough to defeat a general law.

Here is one in the domain of electromagnetic waves propagation in crystals: as demonstrated by Brillouin, there are bandpasses where waves are totally attenuated, while they propagate unattenuated between these bands - this property of crystal lattices has made possible the development of transistors... This is a clear case where you can observe that a lower frequency wave will propagate far less that an higher one.

A second counter-example can be found in underwater sound propagation, as the relaxation phenomenon of magnesium sulfate and also of the boric acid are attenuating specifically some low frequencies far more than higher one.

I am sure there are plenty of similar counter-examples in all the domains where waves can propagate in real media of significant complexity.

So yes, as suggested by Leonard, be humble when attempting to generalize physical laws!

PS for F=M*gamma, the law is probably defeated by examples found from the relativity theory... but I agree I don't experienced exceptions in the Galilee world we can perceive ourselves.

Howdy Bernard,

Your response reminds one of Albert Einstein's response to the publication "100 Scientists Against Einstein," namely, "If I were wrong, one is enough." (It is also cited as "One Hundred Authors Against Einstein.) I affirm that concept without hesitation, however, it seems you and I see Borys Discussion topic differently.

Had Borys stated a theory instead of posing a postulate for discussion, and had he not asked for assistance to understand how the postulate that he based on data could be valid physical science, then the replies he has received would be responsive. For me, a response to his quest for the physical processes of acoustic attenuation as a function of wavelength within the scope of the research he has cited and referenced is hard to find in the many sound, and quasi-sound, treatments of his postulate as a theory.

Granted, Borys Discussion topic statement is strong and he does assert that a general law applies, but the fine print, the discussion of acoustic wave propagation, the focus on wavelength and the question of attenuation due to oscillation rather than resonance (important to frequency discussions) opens an opportunity for a learned person to provide details of that attenuation process. That is what I understand Borys to have requested, and I certainly would like to see such a presentation.

Happy Trails, Len

I propose to discuss the data on wind waves. This is a preprint of "REGULARITY OF THE PROCESS OF ABSORPTION OF ENERGY OF WAVES ON THE EXAMPLE OF THE PROPAGATION OF LONGITUDINAL (SOUND) AND TRANSVERSE (SURFACE) WAVES IN WATER". What is the difference between longitudinal (acoustic) waves and transverse (wind) waves in water? Acoustic waves have practically no dispersion. The speed of sound in water is the same for almost the entire frequency range and is determined only by density (the total mass of molecules and their associations) and compressibility. Phase velocity, wavelength and wave period are constant. As the wave propagates in water, only the energy of the wave (acoustic pressure) changes. Transverse (wind) waves in water are characterized by dispersion с=√(gλ/2π). Ensuring the constancy of the frequency of transverse waves is realized by changing the length and phase velocity of the wave. It is important to note that the wave height, as a characteristic of its energy, is not included in the equations for calculating the phase velocity, period, and angular velocity of the wind wave. Usually, the wave height is associated with the radius of the particle's orbit in the wave https://search.rsl.ru/ru/record/01006934294. Obviously, acoustic and wind waves have significant differences. We analyzed the known facts about the attenuation of transverse (wind) waves with depth. With increasing depth, the radius of the particle's orbit, like half the height of the wave, decreases in accordance with the well-known empirical formula in which the argument is the frequency of the wave https://search.rsl.ru/ru/record/01006934294. Because of this, researchers may also get the wrong impression about the frequency dependence of the shear wave attenuation. It has been established (https://search.rsl.ru/ru/record/01006934294) that a wave with a cycle length of 10 m at a depth at a depth of 1 cycle (10 m) will be 0.002 of its height at the surface; a wave with a cycle length of 100 m at a depth of 1 cycle (100 m) will also be 0.002 of its height at the surface and a wave with a cycle length of 1000 m at a depth of 1 cycle (1000 m) will be 0.002 of its height at the surface. Conclusion. The process of attenuation in water of more complex transverse waves is identical to the process of attenuation of simpler longitudinal waves. See preprint. "REGULARITY OF THE WAVE ENERGY ABSORPTION PROCESS AS AN EXAMPLE OF THE PROPAGATION OF ACOUSTIC WAVES IN WATER". Sincerely, Boris.

Dear Bernard Garnier, The discussion became concrete. Your first argument is "Here is one in the domain of electromagnetic waves propagation in crystals: as demonstrated by Brillouin, there are bandpasses where waves are totally attenuated, while they propagate unattenuated between these bands - this property of crystal lattices has made possible the development of transistors... This is a clear case where you can observe that a lower frequency wave will propagate far less that an higher one." An interesting situation arises. If you know the difference between electromagnetic and mechanical waves, then using this argument I regard as they say in boxing - "low blow". Let's see your answer in the discussion "Is there any direct relation between Acoustic or mechanical waves and Electromagnetic waves?". I quote your answer: "From a physical perspective, no...". No comments... Second argument: "phenomenon of magnesium sulfate and also of the boric acid are attenuating specifically some low frequencies far more than higher one". You are in luck. My colleagues and I devoted a lot of time and effort to this phenomenon and acquired a high level of competence. I will give you a statement from the hydroacoustic theory of sound relaxation in liquids. Relaxation absorption of sound in liquids is always accompanied by sound dispersion. In water, in contrast to other liquids, there is practically no sound dispersion, and at the relaxation frequencies of magnesium borates and sulfates, no increase in sound dispersion is recorded. Sincerely, Boris Kapochkin.