Wikipedia:Reference desk/Archives/Science/2018 July 28

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July 28

Hearing: difference in sensitivity to harmonics and intermodulation.

The reproduction of sound through electronic devices inherently involves "non-linear distortion". It has been known for a very long time that distortion occurs in two forms: harmonic (extra tones in harmonic relationship to source fundamentals) and intermodulation (non-harmonic extra tones that are the sum or subtraction of source tones), and that the ear is both more sensitive to, and finds it more objectionable, to the intermodulation form. For example, the motion picture industry devised a specification and test (the SMPTE test) for maximum allowable intermodulation almost as soon as sound movies were devised. Harmonic distortion they weren't much concerned about.

It seems that this extra sensitivity to intermod is inherent in the structure of the inner ear. Almost all natural sounds contain lots of harmonics. Intermod pretty much does not occur in nature. Does anyone know what evolutionary advantage this has conferred, remembering that human evolution is essentially stopped at the caveman era, or perhaps at the stone age era, when there was certainly no high quality electronic sound? Or is it that excess sensitivity to intermod conferred no evolutionary disadvantage? One would think that as harmonics are normal in nature, that that is what we ought to be most sensitive to. 118.209.51.33 (talk) 16:37, 28 July 2018 (UTC)

Evolution hasn’t stopped. There was not a ‘direction of travel’ of evolution to arrive at where we are now, for humans, giraffes, hippopotami, or dinosaurs etc. — Preceding unsigned comment added by 82.38.221.49 (talk) 17:30, 28 July 2018 (UTC)

So? How does that help?118.209.58.85 (talk) 16:24, 29 July 2018 (UTC)

Human hearing ability has ceased to be a parameter for evolutionary selection since our hominid ancestors struggled in a predatory environment. Our hearing sensitivity and frequency range have become inferior to the cats and dogs around us, though we claim to have developed a finer tuned cultural appreciation of sound (music) than they. We also value our hearing directionality, a hangover from the use of hearing in stealthy stalking or predator avoidance, enough to invest in Stereophonic sound reproducers. This direction sensitivity depends on relative signal phases at each ear (compare with Phased array ultrasonics). A reason intermodulation tones are objectionable is that they can only confuse detection of a sound's direction while harmonic distortion of a single tone does not impede hearing where it originates. DroneB (talk) 13:20, 30 July 2018 (UTC)

No. While GROSS intermodulation distortion (several percent of total sound energy) can make perception of direction difficult, the ear can detect intermodulation at far lower levels, and find these levels unpleasant. Electronic engineers has found it necessary to get intermod in sound equipment below 0.1%. OP121.44.191.221 (talk) 02:35, 31 July 2018 (UTC)

In case it's still not clear to the OP, when your conclusion is based on a faulty premise, it could easily be flawed. The idea that human evolution basically stopped at the stone age or the caveman era is not generally accepted as true. (It's true that some evolutionary biologists have made that argument but I wouldn't say it's widely supported [1] and even for those who have made it, I don't think they intended it to be taken the way some e.g. in the paleo movement have done. And obvious reason is it's easy to find examples which show it's untrue e.g. lactose persistence or the various genetic resistance to malaria.) To be fair, I'm not sure if this particular premise matters so much. If you're right that intermodulation distortion basically only really occurs with electronic (or even electric) sound, and not with other forms of human induced sounds, I think few would suggest there has been sufficient evolutionary pressure to result in such a significant shift in how we hear it that it's something that is widely untolerable. However the wider point remains that if you are coming to a conclusion, you need to be sure your premises are correct and lead to those conclusions. Nil Einne (talk) 19:55, 30 July 2018 (UTC)

Evolution in humans has essentially stopped. That is something that is abundantly clear. It is true that some think it hasn't but then some people believe the Earth is flat, and some don't believe in evolution at all, and have got laws in some US states to ban teaching it. And if you think humans have evolved to enjoy electronically reproduced sound (pretty much the only source of intermodulation), then you must be on a substance. But in any case, all this has actually little to do with my question. OP121.44.191.221 (talk) 02:35, 31 July 2018 (UTC)

No credible astronomer or physicist believes the earth is flat. Probably most evolutionary biologists do not accept human evolution stopped in the stone age or cave age, as per my ref. There is a big difference. As for your second point, it has nothing to do with what I actually said since I specifically noted that if intermodulation truly arose with electronic or electric sound, it is unlikely anyone would credibly suggest there was sufficient selective pressure to cause it to have arisen. As for your third point, I already explained why it has to do with your question. If you are unwilling to accept you may be wrong, or think being wrong makes you an idiot, that's your choice, but it means you are unlikely to be able to get any help on the RD. Nil Einne (talk) 05:09, 31 July 2018 (UTC)

If I understand this question, the OP is asking whether the aesthetic appreciation for sound is derived from an evolutionary tendency - and in specific, if there is an evolutionary reason to prefer certain harmonic tones, as opposed to non-harmonic combinations.

The answer should be a clear and sonorous no, this aesthetic preference is not an evolutionary effect; this is a learned, acculturated phenomenon related to the history and culture that has had a dominant effect on the music and sounds that many of our readers are exposed to.

Our article on Tonality is a good starting place; and our ancillary article, Atonality, has this to say: "the term atonality describes music that does not conform to the system of tonal hierarchies that characterized classical European music between the seventeenth and nineteenth centuries..." (with just massive amounts of citations to great music-theory sources all throughout that article).

So: no, we humans did not have any evolutionary or biological reason to prefer harmonic sounds, nor was there any evolutionary reason to dislike nonharmonic sounds (including, but not limited, to the sounds caused specifically by intermodulation of acoustic frequencies). Any such predisposition that you or others may have is a learned behavior that is heavily influenced by your exposure to the musical traditions of renaissance-era Western European societies, and the more subsequent modern music that developed from those cultures.

Nimur (talk) 05:13, 30 July 2018 (UTC)

These are very definitive statements, but I'm not convinced that they are correct. Harmony actually has a very strong and straightforward physical significance. When you have a simple source of sound, it usually produces a base frequency and a set of "harmonics", that is, tones with frequencies that are integer multiples of the base frequency. As the name indicates, the harmonics harmonize with each other. When you have multiple sound sources, the tones that they produce typically do not harmonize with each other. Therefore, harmony is a signal that a sound comes from a single source. Thus, the ability to perceive harmony goes with the ability to distinguish single sound sources from multiple sound sources. I can't prove that that has evolutionary importance, but it does seem plausible to me. Looie496 (talk) 14:44, 30 July 2018 (UTC)

It sounds like the OP is saying we shouldn't really hear or care about intermodulation distortion much because it rarely occurs in nature so it's not something the ear should have evolved sensitivity to. They are therefore wondering if the structure of the inner ear evolved in such a way to cause sensitivity to intermodulation distortion and why it would have done so. Or if alternatively because intermodulation did not occur, there was no reason for us to evolve to have little sensitivity to it but there was for harmonic distortion. Personally I think the OP's question is based on too many faulty assumptions and misunderstandings, but I'm not sure if Nimur's answer really properly addresses them. Nil Einne (talk) 19:55, 30 July 2018 (UTC)

I don't know enough and haven't put in the time to riddle this out, but there is a lot about harmonics in the cochlea, e.g. [2] I would speculate that there may be a difference in how much the two types of distortion affects the final neural signal, but I don't know that. Wnt (talk) 14:36, 30 July 2018 (UTC)

The unpleasantness of IM (intermodulation distortion) is the reason loudspeakers for music are constructed with multiple transducers in the same enclosure, each reproducing only a part of the audible frequency range. Is it feasible, either theoretically or on practice, to remove IM from an old recording by modelling and inverting the signal non-linearity? DroneB (talk) 00:24, 31 July 2018 (UTC)

This is off topic, but you are correct about loudspeakers. It is theoretically possible to remove intermod from old recordings to some extent, but in practice its extremely difficult and usually impossible. There are essentially three reasons why it is extremely difficult:-

Many musical instruments have a tonal structure that is not precisely harmonically related. Snare drums have a large number of frequencies in their sound, but they are NOT harmonically related. Pianos are tuned so that the string relationship is close to harmony, but not exact. Some pianos (eg honky-tonk) are quite well off harmony. The human voice contains overtones that are not harmonically related.

I was once engaged in the design and manufacture of guitar amplifiers. It's one thing you learn in that business, it's that if there is some effect or artifact, some musician somewhere will devise a way to exploit it in a hit tune. For example, fuzz, widely used in rock and to some extent in jazz, is gross distortion. How does some machine identify what's unwanted distortion, and what's not?

The number of additional tones created by intermod rapidly becomes very large as the number of tones in the source sound increases. You would need a warehouse full of supercomputers to figure it out, for any but the acoustically simplest of recordings.

Note that an overtone structure, such as the human voice or a piano, or percussion instruments, is NOT imtermodulation, and doesn't sound like it, but its still additional tones just as intermod is, so is diffult to distinguish mathematically. OP 121.44.191.221 (talk) 03:00, 31 July 2018 (UTC)

I appreciate the time and effort by everyone who responded (except Nil Einne, who works on the basis of "I don't know how to answer this, so lets just say the OP is an idiot". Just what misconceptions have I displayed??), but you are all off track. I'll try and clarify my question: Human hearing is more sensitive to small amounts of intermodulation distortion (something not experienced by humans until the invention of radio and movie sound tracks) than it is to harmonic distortion (also an artificial thing). This seems to be inherent to the structure of the inner ear. Is there a possible evolutionary reason why we ended up with that structure, noting that sensitivity to intermod has little or no benefit in nature? My question has nothing to do with tonality or appreciation of Western music. As the motion picture industry quickly found out 100 years ago, intermod is objectionable at very low amounts, regardless of whether it's voice, music, or sound effects.

Since intermod almost never occurs in nature, I am assuming that the ear's sensitivity to it is an accidental by-product of a solution that was a response to some evolutionary pressure, which must have been prehistoric and most likely goes back to the appearance of early mammals or even earlier. OP121.44.191.221 (talk) 03:24, 31 July 2018 (UTC)

Except I never said you were an idiot. I'm not sure why you believe being wrong makes you an idiot, but that's your own problem. It's clear from all my responses that I'm acknowledging that your understanding of audio physics appears to be significantly greater than mine, so it's even less clear why you believe I would call someone an idiot despite their understanding on one area clearly being greatly superior to mine. Both me an the other IP specifically noted your points on evolution are largely incorrect. I provided a ref demonstrating part of this. I also tried to understand what you were asking, and from what I can tell I understood it better that what Nimur did. I attempted to help you by trying to explain what you were asking since I believed, and from your response I believed correctly, that it had been misunderstood and so Nimur's response wasn't really addressing it. In fact your clarification is very close to what I was already thinking, and what I tried to convey with my response to Nimur and Looie496, My mistake for trying to help. Nil Einne (talk) 05:09, 31 July 2018 (UTC)

Yes, of all the responders, you came closest to understanding what I was asking. You mentioned that I thought that as intermod pretty much does not occur in nature, there cannot have been any direct evolutionary pressure to acquire sensitivity to it. It must have been a by-product of some other pressure. Note that harmonic distortion also is not a natural phenomena - it too is an artifact of electronic sound reproduction. However you stated "the OP's question is based on too many faulty assumptions and misunderstandings." But you did not explain/describe just what those assumptions and misunderstandings were. And you could have just declined to post. So, the inference is clear - you think my question is stupid and does not merit an answer. If you had explained/described what was wrong, that would have helped. Or, to put it more plain - you think I'm an idiot (which might well be the case), but isn't the purpose of this website to help, idiots or whatever?

I wish I had not said evolution in humans had effectively stopped. That actually has no real bearing on the question, except that it is obvious that we cannot have evolved to listen to electronic reproduction, and it has caused people to go off on a tangent (eg the "other IP" you mentioned). The human ear has certainly not changed in that time. In fact its really the old Mark XX Mammalian Pattern Ear, with a good brain attached that can understand advanced speech. OP 121.44.191.221 (talk) 05:32, 31 July 2018 (UTC)

I will not be responding further for reasons I will outline on the RDthis latest IP talk page. Nil Einne (talk) 05:36, 31 July 2018 (UTC)

I was mystified by Nil Einne's mentioning of "IP talk page" until it occurred to me to just click on <talk> after my IP. Click on it and you'll see Nil Einne's got his knickers twisted. Oh well. If someone has a go at answering my question, that's great - I can assure you any genuine help will be appreciated. If not, well, I am unlikely to post any more questions. OP118.209.32.109 (talk) 06:52, 31 July 2018 (UTC)

Red meat and diabetes

Red meat says A 2016 literature review found that for the each additional 50g per day of processed meat (e.g., bacon, ham, hot dogs, sausages) consumed, the risk increased 4% for total prostate cancer, 8% for cancer mortality, 9% for breast cancer, 18% for colorectal cancer, 19% for pancreatic cancer, 13% for stroke, 24% for cardiovascular mortality and 32% for diabetes. The source is [3] ("Free Access"; not sure if that means it's open access or that I can access it due to my on-campus IP address), and most of its references to diabetes are merely comments; the exceptions are Table 1, Figure 2, and Figure 3. [Figure 3 proposes a mechanism whereby various chemicals in red meat trigger insulin resistance.] Am I missing something, or does the author merely give the statistics (with sources, of course) and propose an explanation, or does he give methodology somewhere? Here in the USA, at least, individuals with higher consumption of red meat have disproportionately high rates of general poor eating, including obvious diabetes-associated sugary foods. If the latter, it's still a reasonable thing to state in a research article because it poses a topic for research ("does red meat cause diabetes, or is it associated with something else that causes it?"), but by stating this information where we do in Red meat, we're implying causation, which isn't seemingly appropriate unless the author's reviewing studies with control groups whose diets were similar minus the red meat. Nyttend (talk) 17:06, 28 July 2018 (UTC)

These are just correlations that may disappear after appropriate adjustments as already mentioned in the article. Ruslik_Zero 17:40, 28 July 2018 (UTC)

AFAIK, red meat increases bowel and colon cancer from 4-5% to 5-6%, i.e. if one consumes lots of read meant for most of his/her life. Tgeorgescu (talk) 04:17, 29 July 2018 (UTC)

A study I assisted, which resulted in a publication titled "A Prospective Study of Red Meat Consumption and Type 2 Diabetes in Middle-Aged and Elderly Women," found that there is a positive correlation between red meat and/or processed meat intake and type 2 diabetes. IT was limited to a population of about 35k women age 45+. The risk was adjusted for multiple know variables. The ending correlation was very small, but significant. The highest correlated subgroup was bacon followed by hot dogs. 209.149.113.5 (talk) 17:19, 30 July 2018 (UTC)

Link to 209.149.113.5's study. Thank you! Nyttend (talk) 01:23, 31 July 2018 (UTC)

Type-2 diabetes is caused by eating fat. Count Iblis (talk) 19:32, 30 July 2018 (UTC)

See Cherry picking and WP:MEDRS. Your source is crap, and as you always do, you enforce your peculiar singular opinions about nutrition on the reference desk by finding sources of questionable reliability that ex post facto conform to your peculiar, otherwise unsupported beliefs. Lifestyle causes of diabetes mellitus type 2 does not make it out so simple, and unlike the shit source you just posted, does itself reference several well-respected peer-reviewed journals. Yes, fat intake is linked partially to type 2 diabetes, but you, and that article, make a definitive, direct causal link that actual reliable sources don't. There is not a one-to-one correspondence, and correlations between fat intake and the disease in question are only one of the melange of possible causes of the disease. Please just stop, and keep it to yourself from now on. Saying nothing at all is more helpful than spewing crap like this.--Jayron32 02:52, 31 July 2018 (UTC)

I feel a big issue is use of the word "significant" in correlation studies. It doesn't mean "important" or "extensive." It means "cannot be solely attributed to random factors within the confines of our study." So, if I do a study and I find that there is an extremely weak, but "significant," correlation between fat intake and DM, a non-scientific person might think that I am saying fat intake and diabetes have a significant, e.g. important or extensive, relationship. What I'm really saying is that I haven't been able to completely rule out the correlation as random. Sometimes it turns out to make sense. Beta blocker usage and lip cancer have a significant correlation and, currently, doctors advise beta blocker users to apply SPF lip balm or wide-brim hats. Also, Februrary (regardless of the hemisphere) and raised blood pressure have a significant correlation. Why? There is no known reason because the effect is worldwide. So, you can't blame the cold (it is warm in the Southern Hemisphere in February). You can't blame air pressure or humidity, which is different all around the world. You can't blame diet. That month holds no significant worldwide diet change. It is just than when the Earth is in a certain position relative to the Sun, more than half the humans appear to have slightly raised blood pressure. In this case, significant simply means we haven't found a way to rule it out as random (yet). 209.149.113.5 (talk) 12:54, 31 July 2018 (UTC)

(ec) @Jayron32: There's no sense getting too carried away, because the Wikipedia article you link makes the same claim as the one Count Iblis linked ... though it is far more restrained in its wording.

To be sure though, there are also relevant foods with a positive role -- cinnamon and cassia, the most commonly used traditional Chinese drugs for the disease, which at the very least are a useful source of dietary fiber for weight loss, and may have other chemicals of note, apples, whose pectin can reduce sugar spikes in the short term, broccoli which contains glucoraphanin. Also coffee has been reported to reduce the risk of the condition -- though oddly, searching now I see this effect attributed to cafestol, which isn't the compound I thought they said before. Wnt (talk) 12:58, 31 July 2018 (UTC)

The problem doesn't have much to do with the evidence, rather the fact that the general population has a lifestyle that's so extremely unhealthy that the general lifestyle advice is more about damage control than giving advice on what's optimal for a people who are willing to go the extra mile. Let's take a look at this news report. Let's accept the results as "the truth" for argument's sake. So, let's assume that 800 grams of fruits + vegetables is indeed a lot better than 400 grams. Then under that assumption, the official advice would still not change, because, as the asrticle says: "Dr Aune said the findings did not mean the five-a-day message needed to change. He told the BBC: "There are many different considerations if changing policy, it's not just the health effects - is it feasible? " and "Dr Alison Tedstone, chief nutritionist at Public Health England, said: "The five-a-day target is the foundation of a healthy balanced diet and is an achievable way to help prevent a number of diseases.

"Whilst consuming more than five portions of fruit and vegetables a day may be desirable... adding pressure to consume more fruit and vegetables creates an unrealistic expectation.""

So, when Jayron is eating his steak with some potatoes and vegetables floating in fat, he thinks that's not too bad because he is still sticking to the "five-a day message". So, why give that up and eat like Count Iblis? The answer is given here, and here, and in the link I gave above that Jayron dismissed as a crap source. This article is worth reading, it mentions how Alderman dismisses the science on salt intake just like Jayron does here on fat intake. Count Iblis (talk) 17:02, 31 July 2018 (UTC)

Why are you telling me what I eat? I've never had a meal with you, to my recollection. I've never tried to give advice to people on what to, and not to eat, not the least of which by cherry picking sources. I didn't say you should be giving different advice to people. I've said you shouldn't be giving advice to people. Keep it to yourself, is what I said. --Jayron32 12:00, 1 August 2018 (UTC)

I didn't give any advice to people. That eating fat in the quantities most people do is extremely harmful for health is a hard, rigorously proven fact. It's not medical advice to say so, as it doesn't imply any advice on how to eat healthier. Now, the fact that this is controversial within medical science, is because medical science isn't a hard science like physics or chemistry. You cited WP:MEDRS, but this paints a rosy picture about how reliable the most reliable sources in medicine are. In reality a lot of junk gets published in the top medical journals. In a field like physics, Dr. Alderman mentioned in this article and in this one couldn't possibly have gotten away with doing his research in the way he goes about it. It would be considered to be outright scientific fraud, but in medicine this is acceptable. As mentioned in the second article: "As usual, Alderman, a coauthor, has once again failed to declare that he has worked over many years as a consultant to the Salt Institute. As editor-in-chief of the American Journal of Hypertension, this could be viewed as a very serious conflict of interest." Count Iblis (talk) 20:06, 1 August 2018 (UTC)

Also, we need to note here that the link between lifestyle and T2D is context dependent. What passes for lifestyle factors in diseases in most sources is actually the effect of an even worse lifestyle than sticking to the (not so healthy) norm. E.g. in an absolute sense, the Mediterranean diet would have to be considered to a be a rather unhealthy diet, because the people who stick to such a diet have massively higher rates of heart disease and strokes than the Tsimané people: "Heart attacks and strokes are almost unknown amongst the Tsimané thanks to a high carbohydrate, low protein diet and active lifestyle, say researchers". Count Iblis (talk) 17:30, 31 July 2018 (UTC)

Tractor model (Montana 1991)

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Which model is this tractor? --Nato-Strichmännchen (talk) 19:09, 28 July 2018 (UTC)

Looks like an older model of the Massey Ferguson 230. It seems definitively from this company.--Doroletho (talk) 12:18, 29 July 2018 (UTC)

Dissenting opinion: wrong front suspension for a MF, wrong color for a 230, wrong grill, etc. The color, grill and front suspension suggests Minneapolis-Moline to me. Cf: grill here and suspension here. Can't place the model, however. 2606:A000:1126:4CA:0:98F2:CFF6:1782 (talk) 21:04, 31 July 2018 (UTC) . . . Very similar to 1962 MINNEAPOLIS MOLINE GVI