Wikipedia:Reference desk/Archives/Science/2019 April 19

= April 19 =

Fear of too many moving objects
Is there a name for a fear of too many moving objects? I know a few people who have this. For example, if they see a big school of sardines on tv, they get upset. Anna Frodesiak (talk) 05:23, 19 April 2019 (UTC)
 * Googling the subject yields the term "kinetophobia", which Wikipedia does not have a separate article about. ←Baseball Bugs What's up, Doc? carrots→ 09:06, 19 April 2019 (UTC)
 * Kinetophobia symptoms, causes, treatments, etc. also known as kinesophobia. DroneB (talk) 11:14, 19 April 2019 (UTC)


 * Well, I'll be darned. Thanks folks. There is Articles for deletion/Kinetophobia. So, article-worthy? Anna Frodesiak (talk) 11:23, 19 April 2019 (UTC)
 * Wikipedia has the sum of human knowledge. Except when it doesn't. ←Baseball Bugs What's up, Doc? carrots→ 18:07, 19 April 2019 (UTC)


 * Hang on, this seems like a different thing. Anna Frodesiak (talk) 11:25, 19 April 2019 (UTC)
 * We mere mortals cannot see that link. ←Baseball Bugs What's up, Doc? carrots→ 18:06, 19 April 2019 (UTC)
 * Sorry Baseball Bugs. Yes, that deleted article refers to Kinetophobia as fear of moving one's own body in, say, physiotherapy because it might hurt. Anna Frodesiak (talk) 05:03, 21 April 2019 (UTC)


 * Many phobia names are coined without any clinical meaning behind them. They're not regulated, per se, so if you suffer from some anxiety about something you can just make up a -phobia name for it. See List of phobias, especially the text at the top, for more on this phenomenon. Note that many of the phobias on that list (of which kinetophobia is not one) are stubs of questionable encyclopedic value. I would be surprised if many do not meet the same fate as the one above. Matt Deres (talk) 12:46, 19 April 2019 (UTC)


 * I suspect surviving something like this would cause an extreme version of this fear :-) BK really was an amazing performer. MarnetteD&#124;Talk 18:14, 19 April 2019 (UTC)

It would surprise me if this wasn't a thing. A quick web search finds a repeated passage about kids with autism:
 * In fact, 70 years ago, Leo Kanner wrote in his initial account of autism that “loud noises and moving objects” are “reacted to with horror” and things like “tricycles, swings, elevators, vacuum cleaners, running water, gas burners, mechanical toys, egg beaters, even the wind could on occasions bring about a major panic.”

though that doesn't seem limited to large numbers of moving objects. 67.164.113.165 (talk) 07:02, 20 April 2019 (UTC)

Thanks all. So, I guess there's nothing good out there that identifies this as a phobia where people freak out if too many crawling ants are on tv. Cheers. Anna Frodesiak (talk) 05:03, 21 April 2019 (UTC)
 * Well, if some people do, then it's a phobia. Things still exist whether or not they have been named yet, and also if they have been named but we (who are not qualified psychiatrists) are not sure what the appropriate name is. {The poster formerly known as 87.91.230.195} 2.122.2.132 (talk) 07:01, 21 April 2019 (UTC)
 * Thank you kindly. I guess I'll just wait until more info becomes available. Anna Frodesiak (talk) 07:01, 22 April 2019 (UTC)
 * This phenomenon has been repeatedly used in movies. Think of the Star Wars battle scenes where a host of TIE fighters come zooming into view. Or the Indiana Jones scenes with various creepy-crawlers. Or any western movie where hundreds of Indians come roaring downhill. Or maybe even The Birds, with large numbers of gulls and crows turning malevolent. However, those things are more than just phobias - they are genuine threats to one's well-being. ←Baseball Bugs What's up, Doc? carrots→ 07:18, 22 April 2019 (UTC)
 * It seems kind of like a cousin to Trypophobia, which isn't an "official" phobia either, but apparently has had plenty of commentary on it. ←Baseball Bugs What's up, Doc? carrots→ 07:21, 22 April 2019 (UTC)
 * As pure speculation, I posit that a large multiplicity of moving objects, even if small and unthreatening in themselves, could be unsettling because it is beyond one's brain capacity to keep track of them. A corollary would be that if the movements are more predictable, as in snow falling, less anxiety would result than if the movements are less predictable, as in a swarm of ants. The article Sensory overload may be of some relevence. {The poster formerly known as 87.81.230.195} 2.122.2.132 (talk) —Preceding undated comment added 11:31, 22 April 2019 (UTC)
 * I, for one, find watching a school of fish pleasant and relaxing. I think most do. Maybe that is because they interact. But I would guess that even ants all going in different directions do not distress people. However, watching a swarm of rats, cockroaches, lobbyists, or insurance salesmen, now that's a different matter. Maybe that is because they have a relationship to the viewer. Anna Frodesiak (talk) 03:22, 23 April 2019 (UTC)

Double bass sound
How can the acoustic double bass produce audible frequencies below those supported by internal  maximum dimension of the body? Ie. Body max internal dimension is about 1.5m, but the lower frequency (E1) is at 41 Hz. 80.2.20.230 (talk) 19:55, 19 April 2019 (UTC)


 * If the linear density of the strings is high enough, then the lower frequencies are achievable. Mikenorton (talk) 20:53, 19 April 2019 (UTC)
 * When vocal cords vibrate at a low frequency then a bass sound is produced. It is not required to resonate in any cavity. Ruslik_ Zero 20:58, 19 April 2019 (UTC)
 * Subharmonics? 67.164.113.165 (talk) 07:04, 20 April 2019 (UTC)
 * so if the strings make the sound alone, why do you need that big doghouse? My question related to the size of the resonant cavity used for so called ampl7fication of the low frequencies. If the body is not large enough to be resonant at the low frequencies, how can it project rhe sound into the air? So how does a double bass produce those low frequency fundamentals, or does it?80.2.20.166 (talk) 13:46, 20 April 2019 (UTC)
 * You are incorrect in your assumption that the body of a stringed instrument does not increase the projected volume below resonance. See the measurements at . --Guy Macon (talk) 14:42, 20 April 2019 (UTC)
 * Hmm. Did you actually read Zevins report? If so, you will have noticed that his resonance tests on the double bass (Fig 7), show no (or very little) response below about 120Hz when excited from between 10Hz and 1000Hz by a transducer. This is because the body of the bass is not large enough for any lower resonance. If we consider the (internal) resonant chamber dimensions of a typical double bass as being about 4.5 feet maximum in any direction, we can see this length corresopnds approximately to a half wavelength of sound in air of about 120Hz. Is this a coincidence?

So my question remains: How does one percieve low pitch sounds that the double bass body plainly cannot generate? 213.205.242.157 (talk) 18:48, 20 April 2019 (UTC)
 * The E1 string of a Double bass vibrates at 41.2 Hz, something you can both see and hear even if the string were suspended between unyielding solid supports. The mass of air moved directly by the thin string is tiny and that source of sound is almost neglible. However in this instrument, as with others in the Violin family, a bridge transmits string vibrations to the large-area soundboard i.e. the front face of the instrument. This soundboard is flexible, it serves to couple the string vibrations to a large air mass and that is how a clearly perceptible volume of sound is achieved. The question seems to imply that Helmholtz resonance of the double bass body cavity is essential to all sound production but that is not so. The distinctive perceived musical quality of the E1 note from this instrument depends on the wide range of harmonic and non-harmonic frequency components generated by the player stroking the bow against a part of the string. Body resonances, both of the enclosed cavity and of the body structure affect most of the audible frequency range but the fundamental frequency of the E1 note is, in isolation as considered by the question, a pure sinusoidal wave of lesser musical interest. DroneB (talk) 20:27, 20 April 2019 (UTC)
 * so if the Helmholtz resonance of the body is not necessary, why not just use a plain sheet of wood to transmit the vibrations to the air.? If one tried this, i think it would be found that there was very little transmission of the very low frequencies into the air. Also the bass woukd sound lousy as that would be fewer overtones generated. So why can one hear low frequencies that cannot be generated by any element of the instrument. The double bass article is silent on this issue, but it should not be.80.2.21.198 (talk) 21:07, 20 April 2019 (UTC)
 * "not just use a plain sheet of wood to transmit the vibrations to the air". This is because the waves coming from the front and those coming fron the back of the sheet have opposite phases and tend to cancel each other. Using a closed box has the effect that half of the waves are absorbed and cannot interfere with the other half. This has nothing to do with your question. One can hear low frequencies that cannot be generated by any element of the instrument because they can be generate by one element of the instrument, namely by the strings.
 * As DroneB sayd, the box has not the function of generating the sound, but merely of transferring the sound from the strings to the air. For this it doesn't need to be in resonance 2003:F5:6F03:B700:6D81:3AAB:EA46:F350 (talk) 18:36, 21 April 2019 (UTC) Marco Pagliero Berlin
 * A pices of wood only a couple of metres in diameter when excited at its centre is capable of radiating without cancellation down to about 60Hz.(See [Open Baffle]) So why are not double basses made like that? 80.2.21.166 (talk) 19:49, 21 April 2019 (UTC)

DroneB (talk) 21:15, 21 April 2019 (UTC)

I'd guess that disc (besides being a couple metres in diameter) would need quite a a lot more driving energy than a conventional double bass would, because there is no resonating air column. 67.164.113.165 (talk) 23:58, 21 April 2019 (UTC)

My guess is the mass of the skin of the double bass is coupled to the spring provided by the acoustic cavity, and since it weighs a lot more than the air, dominates the sqrt(modulus/density) equation. Mass loading of acoustic cavities is both significant and complex. The equation would be similar to that of a Helmholtz resonator, but the actual determination of the participation of the skin of the instrument would be a very complex calculation. Cheers Greglocock (talk) 00:47, 22 April 2019 (UTC)
 * All very useful comments, but i fear that we are not my moving any closer to the real explanation. Any votes for moving this discussion to talk:double bass? 80.2.21.123 (talk) 20:01, 23 April 2019 (UTC)
 * and another thing: since the bridge is fixed and doesn't move, how does it transmit the string vibrations? The bridge and the nut are both nodes for the vibrating string.80.2.21.123 (talk) 20:42, 23 April 2019 (UTC)
 * The bridge is neither fixed nor rigid. It does move, and its modes of flexing serve as an acoustic filter to some extent. To answer your original question an acoustic driver need not be resonant at the frequency being emitted. String instruments are not highly selective (high Q) resonators, and would sound awful if they were. Some care and skill goes into giving them an even response over their useful pitch range. Just plain Bill (talk) 21:15, 23 April 2019 (UTC)
 * Yes enough now of the hand waving. Let's get down to the physics of the problem .80.2.21.123 (talk) 20:48, 23 April 2019 (UTC)