h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

By the way, no one has yet said what item he acquired from the orchestra!

Riddle me that, and THEN this QI is complete!

A tuning fork?

Not sure how this could be complete. Nobody's mentioned the motive, or what earth-shattering event is about to happen.

Yes.

The G6 Tuning fork. +3


I'll grab a cup of tea and start writing up the scores.

This QI is concluded, chat amongst yourselves.

So as it turns out the way in which one calibrates a radar gun is to use a tuning fork!

I found that out last week when a new ANPR camera went up at work and I was chatting to the security guard about it and he said, they can calculate a cars speed entering the campus by knowing the distance from the gate, but to get the accurate speed they use the radar gun, by the way, did I know how they calibrate it? When he told me he uses a tuning fork, I thought that was quite interesting (), and that set my cogs turning about turning it into this QI.

So to be clear, the rookie cop works in Traffic Enforcement. He forgot to plug in the radar gun, the batteries were flat, so needed to buy new batteries from the hardware store. However, to make sure it was working he needed to then recalibrate it. So how do you use a tuning fork to calibrate a radar gun? Well it turns out that the National Institute of Standards and Technology, out of Colorado, wrote a paper in 1976 advising the police on exactly how to do this.

http://tf.nist.gov/timefreq/general/pdf/87.pdf

The Tuning forks usually come with the gun as a kit, so you get forks that resonate and give readings for set limits, like 50MPH. The 50Mph standard is usually given as a reading of Hz (cycles per second) so the 50Mph fork is resonating at 1569.54Hz. The above report also says that the degree of error permissible in obtaining a reading is 5Hz (which corresponds to 0.2MPH error, i.e 1MPH at the greatest extent.) By happy chance, the resonance frequency of the note G6 (the 71st key of an 88-piano keyboard) is 1567.94Hz - within the 5Hz permissible error!

Our rookie cop has truly excellent hearing, and could detect that the soprano was singing slightly out of tune, caused by the piano being slightly out of tune, so he figured they'd have the G6 tuning fork to hand - and he was right!

He could use the G6 tuning fork to set the gun to register 50Mph.

The NIST paper notes, that the issue of proper calibration of radar guns requires an ongoing service (set up in 1976) in order to ensure proper application of justice, however, the tuning fork alone was insufficient, and I quote: "Suppose, for example, that a radar instrument [...] was detuned [...] For the protection of all parties, it is essential that both the frequency of the radar signal as well as that of the radar instrument's accompanying tuning fork be certified as correct within accepted tolerances." The report stresses this is all able to be done 'in the field' - so (one of my many conceits, to also include fitting a grand piano into an orchestra and having a hardware store sell radar gun batteries ) I am for the purposes of this QI assuming it was portable and not screwed to the floor.

The on-going calibration service run by the NIST is both a radio and telephone service, broadcast out of Fort Collins, Colorado. The radio station goes by the handle WWV. In case that was confusing to anyone, there is a convention that all radio call signs East of The Mississippi start with a "W" - the wrinkle here is the National Standards Bureau was founded in Washington DC, but now has divisions is Colorado and Hawaii.

To calibrate the frequency of the radar gun itself a frequency counter is used. In order to calibrate to a known that so it can give an accurate reading of the gun's reading of the tuning fork it has to be calibrated too.To give a reliable read out - the NIST WWV broadcasts a continuous 600Hz tone every odd minute for 0-45 seconds; with the exception of minutes 9, 45, 47, 49 (hence why this was set only just after 9am) this can be used with an amplifier and a frequency counter down a phone line to verify the frequency of the tuning fork and the gun. If you were so curious as to know the structure of the NIST tonal pulse regime and all the other natty information that broadcast on that signal, they have a diagram on their website.

http://www.nist.gov/pml/div688/grp40/wwv_format.cfm


So a little before 10pm our rookie cop arrives back at his patrol stop armed with a radar gun fully charged and calibrated.

Speed-freaks of Boulder City, Colorado, beware!


Meanwhile , "whistle for a Soprano" - was an attempt to lead you into various Mafia related klaxons , however the singing range for the Soprani is the flageolet or "whistle" register, and it includes the vocal note G6.



Clive.

QI - "Whistle for a Soprano"
------------------------




Correct (+3)
------------------------
Shagbark (69)
"the opera plays the note he needs"

Shagbark (91)
"G above High C"

Shagbark: (104)
"He asks why the soprano isn't in key" (because their grand piano has been acting up!)

Geggs (122)
"He works for Traffic Enforcement"

Geggs (122)
"The Speaking Clock"

Geggs (145)
"A speed/ radar gun"

Icy North (155)
"A sort of of do-it-yourself attempt to calibrate a speed gun"

MMF (156)
"He changes the batteries but it needs recalibrating so he legs it to the orchestra now it is good to go!"




QI Bonus (+6)
------------------------
MMF (79)
"Hoffnung's Concerto for Vacuum Cleaners"


DGI Bonus (+1)
------------------------
Mu Beta (10)
"Expect it to be tuned before a performance"

SashaQ (21)
"that is certainly a high note"

Mol(41)
"It needed new batteries"

Mol (41)
"makes me think of frequencies"

Superfrencie (119)
"The dial tone when you pick up a phone is 440Hz"

Teaswill (123)
A radio is involved.


Mol (128)
"On the third stroke it will be six twenty-three and fifty seconds, precisely. Beep. Beep. Beep"


MMF (141)
"A trick I was taught for tuning my fiddle."


Klaxon (-5)
------------------------
Whisky (82)
"Using sound to break glass"

Shagbark (104)
"He calls the police station"


Elf Bonus (+2)
------------------------
Clive.




Total to be added or subtracted.
------------------------


Mu +1
SashaQ +1
Mol +3
Superfrenchie +1
Teaswill +1
MMF +10
Shagbark +4
Geggs +9
Icy +3
Clive +2
Whisky -5


MMF So that's box seats at the opera for MMF with a magnificent +10

Geggs conducts proceedings with flair and style, a rousing
performance +9

Shagbark, their star may have dimmed but they can still hit the high notes and they look fabulous in a sequinned over the shoulder one piece +4

but late to the performance, flagged downed and fined, points on their licence, and sent on a rehabilitation course so they can learn the penalty of being obvious, it's Whisky with -5

Hope you all enjoyed that. I certainly did!

I did enjoy that, thank you

Mol

The only thing that bothers me is the process. I can't see how evidence collected with a speed gun calibrated by such a lax procedure that you describe would stand up in court.

Should these devices not be certificated as calibrated, and collected from the police station at the start of duty? I'd challenge any prosecution evidence that a policeman had forgotten to plug the speed gun in, then decided to calibrate it by means of borrowing audio equipment from the nearest convenient musician. Who could certify that the device was accurate?

Great!

Hmm.. well the report is nearly 40 years old, maybe things have come on since 1976? But at least according to the security guard at the research campus where I work the tuning fork is still the standard of measure for radar guns. (The wikipedia article on 'uses of a tuning fork' also seems to imply it is the current method of calibration, and that web-page for the NIST tonal pulse was last updated in 2010.)

https://en.wikipedia.org/wiki/Tuning_fork#Radar_gun_calibration

I admit the 'borrowing the tuning fork from the musician' is a conceit of my own invention simply because the frequencies are so close and fall within the defined range of acceptable tolerance as defined in the report.

I don't think your concerns are trivial, but read the report - this is what they say to do!

So maybe you could fight your case, and maybe even win though perhaps it would just be better overall for all concerned if, while driving through Colorado, you just stuck to the speed limit!

Life must have been tough for Colorado traffic cops around that time. You never knew when Mork would appear upside down in the passenger seat of a jeep, for one thing.

A quite interesting little puzzle Clive. thank you for putting it together.


Geggs

You're welcome.

Enjoyed that.

MMF

Yes, thank you, Clive.

It was fun. I am glad.

I'm sure I've some more QI's rattling around inside my head. I'll keep working on them and just keep an eye out for them!

just wondering you said he "looked fabulous in a sequinned over the shoulder one piece"
Is that my impersonator outfit you have me attending the opera in? I think if it weren't for that one klaxon I would be wearing a Tux.

Check back on my previous QIs I always populate the 1st 2nd 3rd and last spots with imagined roles for the respective players reflecting their rankings in general terms of success or misfortune.

Its a small homage to some of the creative sign-offs Fry used to use to close the show with. Started off as a gag but I rather liked doing it. Since you were tied with Geggs for 2nd but for that klaxon but still a positive score that suggested to me a past-their prime diva still able to belt out a tune.

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