Wikipedia:Reference desk/Archives/Science/2020 November 5

= November 5 =

Why are most disposable face masks blue?
The heading is my question. I am referring to the bulk of the inexpensive, lower end masks being used by the public in most countries during this pandemic. One side is very often blue. Why? HiLo48 (talk) 01:51, 5 November 2020 (UTC)
 * According to surgical mask, masks are blue or green on the outside, so that you know which side is out. Why specifically blue or green, as opposed to some other color, it doesn't say. --Trovatore (talk) 01:59, 5 November 2020 (UTC)
 * It is a social convention that signifies that the mask is equivalent to a surgical mask, and that the mask is being worn more or less properly. The colors are almost always pastel with blue being most common, followed by mint green and yellow. This social convention long predates the current pandemic. Cullen328  Let's discuss it  02:07, 5 November 2020 (UTC)


 * I think blue can signify cleanliness. Urinal deodorizer blocks sometimes use that color. Bus stop (talk) 02:50, 5 November 2020 (UTC)


 * Scrubs worn in surgery are often coloured solid light blue or light green. I think surgical masks match these colours. COVID-19 surgical-mask-style face masks, in turn, often match the colours of real surgical masks. (Masks worn in surgery typically have bands that go behind the head, instead of around the ears.) --Lambiam 09:24, 5 November 2020 (UTC)
 * They are most often pastel green in surgery as green is the opposite of red, this allows any spot of blood or contaminant to be seen quickly and easily, allowing for hygienic replacement. The blue now seen most commonly has the same effect, but blue is a more calming colour and so has been implemented for psychological and mental health reasons.  — Preceding unsigned comment added by 86.157.89.50 (talk) 10:32, 5 November 2020 (UTC)
 * on all of that. -- Jayron 32 12:53, 5 November 2020 (UTC)
 * Wikipedia cites the website Color Meanings for blue being a calming colour, but I wonder why this is considered a reliable source. It is not hard to find book sources, though, claiming the same, although here we are told: "Pale green is physically the most relaxing and calming color in the spectrum." (I did not know that pale green is a spectral colour.) I assume, though, that the stated need for citing the final part is about this having been a reason for its choice. As to blood spots being easily spotted (sorry), white works at least as well. --Lambiam 14:52, 5 November 2020 (UTC)
 * Thank you. -- Jayron 32 17:12, 5 November 2020 (UTC)
 * I suspect one reason for using blue and green for surgical scrubs and the like is to make it easier to spot bits that have fallen into the patients innards. DuncanHill (talk) 14:24, 5 November 2020 (UTC)


 * Surgical garb represents a poorer analogy than urinal refreshers precisely because there could be practical reasons why color could matter in a critical setting. We should be comparing Covid-19 face masks to items in which only superficial appearance matters without any underlying benefits associated with the given color. Bus stop (talk) 16:07, 5 November 2020 (UTC)
 * The particular color may not matter for the covid masks, but the fact that the inside is different from the outside does matter. As surgical mask explains, the outside is coated with a droplet-repellent layer, whereas the inside has an absorbent layer.  --Trovatore (talk) 18:43, 5 November 2020 (UTC)


 * Yes, one side has to be differentiated from the other. There are various means by which such differentiation could be accomplished. Bus stop (talk) 19:59, 5 November 2020 (UTC)


 * The outer layer is made of polypropylene. It is a nearly translucent plastic and it doesn't dye easily. That is why it is used - things don't stick to it. One way to dye it is with salts during the production of the plastic. The two common salts are copper salt (blue) or nickel salt (green). That produces blue and green polypropylene sheets. It is possible to produce other colors, but they are more expensive. So, it really comes down to the cost of the dye. 97.82.165.112 (talk) 18:55, 5 November 2020 (UTC)


 * Sounds very logical. Do you have a source? Any indication that "One way to dye it is with salts during the production of the plastic. The two common salts are copper salt (blue) or nickel salt (green). That produces blue and green polypropylene sheets. It is possible to produce other colors, but they are more expensive. So, it really comes down to the cost of the dye"? Bus stop (talk) 19:55, 5 November 2020 (UTC)


 * I've just seen the sheets produced. I've also worked with hospital supply. Blue is the general color for "non-latex." That has to do with gloves though. Blue goves are nitrile and green ones are latex. Not because they have to be, but because that is just what they use in practice. Because polypropylene usually comes in blue or green, asking for blue makes it obvious to workers that it is non-latex. Nitrile does not have to be blue. That is just requested by hospitals. In the infectios studies lab at the hospital, they ask for blue and red. The blue gloves are worn over the red. If there is a tear in the blue glove, it is very obvious because the red shows through. Then, appropriate protocols are followed. 97.82.165.112 (talk) 21:42, 5 November 2020 (UTC)


 * There are also vinyl gloves made of polyvinyl chloride. The "copper salts" may be Phthalocyanine Blue BN and the "nickel salts" may be Nickel(II) oxide. (Or Phthalocyanine Green G.) Bus stop (talk) 22:26, 5 November 2020 (UTC)
 * I think having green as latex is probably specific to that particularly hospital supply chain. AFAIK, it's much more common for latex examination and laboratory gloves to simply be uncoloured (the yellowish colour you see a lot and also with condoms etc) unless you have a reason for them to be coloured. Blue for nitrile however is somewhat common, useful of course to reduce mistakes with latex allergies. Sterile or surgical gloves or other special purpose gloves may be coloured or coloured different to avoid confusing them with examination gloves, and also as mentioned when double gloving is performed, 2 different contrasting colours may be used so a tear or rip is easy to see. See e.g. [//hourglass-intl.com/does-glove-color-matter/] [//glovenation.com/blogs/default-blog/blog-color-coding-gloves] [//nitrilegloves.com/blog/color-is-important/]. Nil Einne (talk) 05:16, 6 November 2020 (UTC)
 * For clarity when I mentioned laboratory, I meant a general purpose lab like at a university rather than a hospital one. Also the hourglass source claims that different colours are sometimes used for to help reduce cross contamination by assigning specific colours to different parts of the lab. (I assume so it's obvious the wrong glove is being used and needs to be changed as you've moved between areas.) It's also claimed that the dental market tends to have a lot of different colours. Nil Einne (talk) 07:40, 6 November 2020 (UTC)


 * According to The Colour of Medicine, white was the preferred colour in hospitals until 1914 when an American surgeon called Harry Sherman used green, "the complimentary colour to hemaglobin" to avoid dazzle. At around the same time, architect William Ludlow began to advocate pastel blues and greens in hospitals because "white is negative". Alansplodge (talk) 12:04, 6 November 2020 (UTC)


 * Eiffel 65 - Blue (Da Ba Dee) Bus stop (talk) 16:43, 6 November 2020 (UTC)


 * For the longest time, ads for tampons always used blue to represent a decidedly red liquid. Maybe the consumers were aristocrats. Maybe it's a Democrat/Republican thing. I don't know. --   Jack of Oz   [pleasantries]  20:26, 6 November 2020 (UTC)
 * This suggests blue was chosen because it was unlike the colour of any other actual bodily fluids and alsobecauseof the hygeine connection [//www.bustle.com/p/why-do-period-product-commercials-use-blue-liquid-the-practice-has-a-long-bizarre-history-2957963]. It also suggests the decision to actually use blue liquid was itself somewhat revolutionary as prior to that, ads were just women running with white-trousers or similar stuff with no mention made of anything remotely connected to periods. Nil Einne (talk) 16:26, 7 November 2020 (UTC)
 * Another reason, in addition to the aforementioned, is that blue is relatively rare in biology. This makes it a good choice for clearly distinguishing something as artificial, and for contrasting it against things like animal secretions. --47.152.93.24 (talk) 19:49, 8 November 2020 (UTC)
 * The inclusion of a word for "blue" into languages was comparatively recent. 146.200.241.2 (talk) 19:13, 9 November 2020 (UTC)
 * Yes, as distinct from green. Topic: blue-green distinction. --47.152.93.24 (talk) 04:32, 10 November 2020 (UTC)
 * Note that 146.200.241.2 is now blocked, as a sock of a banned user. ←Baseball Bugs What's up, Doc? carrots→ 05:50, 10 November 2020 (UTC)


 * During the First World War, René Leriche developed a simple system to differentiate the aseptic clothes and sheets used in the operating room with the colour blue. Masks, caps and sheets, etc., were all made the same colour. The initiative spread throughout France and from there to other countries.
 * For the green, the journey is more interesting. M.Bitton (talk) 02:24, 13 November 2020 (UTC)

(Learning to) Listen to the (amateur/AM) radio
I noticed that when we are not used to listen to rather low quality AM broadcast, we find it utterly unintelligible, sometimes not even recognizing the language being used. However when we start listening regularly, our comprehension increases. Speculative, I imagine the phenomenon is similar to getting used to an accent and might involve 'filling in' the missing part of the frequency. A similar phenomenon might be when really small children are not able to understand a telephone call (also a case of a narrower frequency band).

Is there any research in this, specially from a psychological perspective? Is there a name for this? --Bumptump (talk) 13:05, 5 November 2020 (UTC)


 * It is an established fact that understanding noise-compromised speech in some language is much more challenging for people for whom this is a second language, even if their proficiency is comparable to that of a native speaker. I think that a reasonable assumption is the amount of exposure; in terms of neural networks, the amount of training data. That also explains the difficulties small children experience with understanding telephone conversations. In a recent paper published in the Journal of Cognitive Neuroscience, entitled "Understanding requires tracking: noise and knowledge interact in bilingual comprehension", this is called "neural entrainment to speech". Using that as a search term in Google Scholar produces many results. --Lambiam 15:15, 5 November 2020 (UTC)
 * On Ham radio, the bandwidth will also be seriously restricted. Perhaps to 300 to 2700 Hz. Also for single side band it is easy to get a frequency error, which makes it much harder to understand. Selective fading can reduce the levels of part of the audio band. Also many receivers add quite a bit of distortion to degrade your experience. A squelch might also clip off the first sounds of an utterance. There is a lot of research into this topic. Graeme Bartlett (talk) 00:42, 6 November 2020 (UTC)
 * Restricting the frequency range to 300 to 2,700 Hz, clipping the amplitude and squelching (silencing) pauses between words are distortions that certainly degrade one's experience of entertainment broadcasts such as music. However these "distortions" are applied deliberately to transmissions in aeronautical, emergency and amateur radio because they improve the intelligibility of low-power communinication speech in noise. A different kind of deliberate distortion is the Comfort noise that is added in domestic telephone receivers to reassure users that a connection is live. See Lombard_effect for some research about perceived intelligibility. 84.209.119.241 (talk) 13:15, 8 November 2020 (UTC)

I remember visiting Italy not speaking any Italian. Because of a mixup on arrival, I had to sit around a train station for close to a whole day. Announcements came over the loudspeakers every minute or so, all saying similar things ("train to Roma boarding on track 5", that sort of thing). At first the announcements sounded like a mush of noise, but then they started to resolve into words, and after some hours I could understand them fairly well because of the word repetition. So that does seem like the effect of a neural net being trained to separate sounds. I noticed the same thing with some other languages: the noise slowly resolves into separate words, before the words themselves take on meaning. The auditory net has to tune in for the linguistic net to get any usable signal. 2602:24A:DE47:BB20:50DE:F402:42A6:A17D (talk) 03:08, 8 November 2020 (UTC)