Right. It's a question of context. And here we all are on a website that is basically purpose built for taking things out of context. We might just need to manage our expections in this regard.
I just think it would be nice if "The Book of PF" was quoted so it's obvious it's a book title, not just a weirdly phrased sentence. After that, yeah, it's pretty obvious whether you care about the topic or can just move on without commenting on your apathy.
Though that's still incomplete, because (more of the context stuff that you just have to know already) the "A" here refers to the frequency-weighting scheme used in the measurement, and not to the reference level (which is SPL).
It should probably be given as: dB(A) SPL, or dB SPL (A-weighted).
Though that's still incomplete, because (more of the context stuff that you just have to know already) the "SPL" here refers to the reference level in air (20 µPa) and not water or oil (1 µPa).
It should probably be given as: dB(A) SPL (1=20 µPa).
Though that's still incomplete, because (more of the context stuff that you just have to know already) the 20 µPa only applies at the standard temperature and pressure.
It should probably be given as: dB(A) SPL (1=20 µPa, T=293 K, P=101.3 kPa, in standard air).
Though that's still incomplete, because (more of the context stuff that you just have to know already) the (A) here is actually the A-weighting curve specified in IEC 61672:2003.
It should probably be given as: dB A-weighted (IEC 61672:2003) SPL (1=20 µPa, T=293 K, P=101.3 kPa, in standard air).
Though that's still incomplete, because (more of the context stuff that you just have to know already) ...
...
The point of communication is to transport information, not pointless pedantry (except for a small subset of the population). Nobody is confused as to what 85 dBA refers to.
Granted, I should have been clearer about my intended point, which is just the hazard of assuming that the letter(s) after the dB tell you the reference, because sometimes they don't.
Youtube channel InCamera did an interesting series of videos showing their use of practical effects in the creation of a submarine-based short. Not directly related to Red October, but folks might find it worth a watch.
At a rough guess from the audio samples, that array is producing an acceptance angle much narrower than any Soundfield mic is capable of. The noise source is only 45 degrees off-axis; I'd say any first-order microphone polar pattern (i.e. those a Soundfield mic is capable of) would capture more of the noise than is demonstrated here.
Of course, you can improve on the rejection of off-axis sound by instead using a microphone with a more specialized polar patten (e.g. a shotgun mic), but then you lose the property of the pattern being steerable merely by signal processing.
Lastly, such an array of dirt cheap pressure sensitive mic capsules with some clever computation behind them strikes me as the sort of thing you could throw Moore's law at, if you could justify the quantity. Whereas, Soundfield mics don't make much sense unless you're working with very precisely machined pressure-gradient capsules.
Still, I get the feeling it'll be a while yet before this technique starts looking viable for audio production work, but it's very interesting.
My dad worked on something similar, when during the 1980s the coal-fired station he worked at had to convert to two-shift operation, from the three-shift operation that it's 1950s design had intended. He described this process as, "bashing hell out the machines to make them do things they weren't designed to."
One interesting detail was that the more rapid startup and cooldown of turbines meant that blade spacing couldn't be as tight as before, reducing efficiency during operation. (The turbine casing has less thermal mass than the rotor, and hence contracts faster during cooldown. The spacing of the blades needs to account for this.)
Would it not be more efficient to increase the mass of the casing so that the blades can remain as they were? or was that a non option for other reasons?
No matter the mass of the casing it will absorb and lose heat over some timescale and will expand and contract, changing dimensions.
The design is optimised so that the blade dimensions and the interior casing diameter closely match to a very high tolerance at the optimal operating tempreture.
The challenge is that the casing material and the blades are made of different materials and these materials will have different coefficients of expansion (although there is some room to 'dope' materials to change the CoE at the xpense of other material properties that can be more desirable).
The CoE means that the two expand at different rates as the tempreture changes - if they are "close" at optimal temp then they will drift away as the temp changes due to not expanding in lock step.
It's a tricky thing to get right.
( Also a challenge in multicoloured glass works as the differing colours must be batched to have similiar properties including matching CoE's so they don't pull away when anealing from hot glass work temps to room temp. )
I remember him from the Squeak Smalltalk mailing list, probably early 2000s. He wrote a set of bindings for the pcre regular expression library, which I used quite a bit, but which was never picked up for inclusion in Squeak (because pcre "isn't portable enough").
And, with his intellectual property hat on, he was a regular source of advice to the Squeak community (none of it in an official capacity, he would hasten to add) as they worked through the process of relicensing from the original Squeak License to MIT.
I had the pleasure of meeting (virtually) Andrew through his work with the Squeak community. I also ran into Robert Woodhead (also virtually) through the game StarWeb[1] which he played and contributed to[2].
Right. And also, the photographer likely wants high ISO film, to be able to take a very short, crisp exposure of the moment of impact, without needing to gamble on the amount of cloud cover, and hence available light.
ISO 1600 colour film will have been available at the time, but was probably pretty poor compared to B&W.
