Page 22 and 23 of their current brochure, triple glazing with 38db NR, Glazing 62D with 44db.
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Velux do, three versions IIRC, at significantly increasing costs. We installed the cheapest of the TG in my son’s attic room a few months ago, and they are noticeably quieter with rain than the previous DG variant - and their U value is better meaning less heat loss. I think one of the others was focused on better sound insulation, and the top model gives the best thermal - but at a quite significantly higher cost.
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Also triple is better for thermal insulation - though one forum member has claimed that isn’t true for British glazing manufacturers, but I think that is comparing poorly made triple with the best double, and certainly is the case for the windows I have researched from continental manufacturers, including those I bought for my own home 12 years ago that were manufactured in Germany.
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Likely far better to just have a standard corner & place a bass trap in it.
As for the talk of non parallel walls, & ceilings, etc again parallel walls/celings are probably a better option as their far more predictable when treating. The amount of angle required for non parallel walls would likely make a pretty strange looking room.
As above, a square room is typically regarded as the worst option due to standing waves. There are a number of formulas posted online with room length vs widths that should be ideal. 22x24 would still be too close to a square to be considered ideal. I recently built a dedicated space in my basement, 12.5 wide by 18.5 long, didn’t get to choose my exact size but I did run the measurements though some of the online ratio’s & I lucked out in that these ratios seem to work fairly well according to them.
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I suppose non parallel walls and floors in theatres and auditoriums are mainly due to the stacked seating requirements.
Regarding the question of designing from scratch, given free reign I would aim for non-parallel walls and ceiling, and large dimensions. But in practical terms people are often limited to a rectangular base. it is best to avoid any two dimensions between parallel walls or parallel floor-ceiling being equal, or a direct simple multiple of another (e.g. 8ft and 16ft).
Non parallel surfaces prevent standing waves, and their associated nodes and concellations.
I posted info on another thread some time ago that is intersting in respect of dimensions, the spreadsheets being potentially useful in decision making, as is guidance like the Cardas Golden Trapagon approach. Link below. The rest of the thread may also be of interest.
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Thanks 
I don’t know near enough about room acoustics to comment on this, my comment was more so to do with typical home environments & making the room easier to treat. The type of angles in an auditorium may be good for sound (would assume they do it for a reason), but as I said these types of angles would make for a strange looking room in a home. Having the walls being out of parallel only a few deg isn’t going to do much to improve the sound, just make it harder to treat properly.
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The Golden ratio is considered the most aesthetically pleasing…
Personally I wouldn’t sweat it. Most Hi-Fi and speakers are voiced to fit in a standard domestic space anyway.
If your after a monitor within a studio space type of sound your best bet would be to converse with a studio installation company.
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Whilst that is generally true in principle there is such a huge range of domestic spaces that may or my not be considered as “standard” that many speakers work better or worse in different rooms, and no amount of “voicing” can do anything about near reflections, though choosing speakers by dispersion characteristics can have an influence on side reflections, nor room resonances or cancellations tger than by simply not reproducing the full frequency range.
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That is interesting. I have read of speaker designers contriving the crossover to make the effect of the tweeters to “appear” more closer together - yet have them non central with other drivers facing towards the outside of the baffle. Much like pro ac
Such designs have the recommendation of orientation - yet give the caveat to try otherwise to help with those troublesome near side reflections.
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Thanks for that clarification, Paul.
Isn’t that the RAH rather than the RFH?
IIRC, the Royal Festival Hall in its early years was particularly criticised for having too “dry” an acoustic. I think Barbirolli complained that climaxes in big orchestral scores sounded weak. Attempts were made to mitigate these problems in subsequent refurbishments, with limited success IMO. The Royal Albert Hall, on the other hand, was reckoned to be the place where even a new work could be guaranteed to be heard twice (because of the echo)! The saucers were an attempt to reduce reflections from the dome.
Roger
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Anecdote - somewhere in the West End of London there was/perhaps still is, a restaurant which had a domed ceiling and mezzanine first floor. Let’s just say it was no place to hold a business lunch – you could hear reflected (& focused) conversations clear as a bell.
HL…chief snooper 
I have seen it claimed that, if you stand in the gallery at the very top of St Paul’s Cathedral in London, you can have a perfectly normal conversation with someone on the other side of the building, because the sound waves take the voice over there.
I have never tried this, but it wouldn’t surprise me, as that Wren fellow was a clever b*gger! Apples, gravity, Master of the Royal Mint, and what have you.
The flying saucers in RAH (referenced by the Beatles in A day in the life), were quite effective. The RFH had a major renovation about 10 or 15 years ago, which I understood completed the improvement of the acoustics to the point where it is now considered very good?
The “whispering gallery”.
Sound mirror that is 200 feet long. A whisper at one end is clearly heard at the other end. Outdated by radar.
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An interesting place, and I was there once when the chap that wrote the history books (Richard Scarth - Mirrors by the Sea and Echoes from the Sky) was guiding, and I had a small film point and shoot camera, that for one of those odd and maybe rare moments was not loaded with film, and my pictures were never recorded…
And architect of my college chapel.
Roger