Well, that's the tale as the Bridgewater bosses purringly tell it, but it's none the less probably true. For as concert halls go, this must be one of the most perfectly insulated in the world. This is not just because the service machinery has been housed in an adjoining building, nor because the auditorium has been wrapped in massive double walls. It's due to something you discover if you wander in the bowels of the place; the entire weight of this 25,000-ton edifice of steel and stone rests not on terra firma, but on hundreds of giant car-springs.
As you clamber up and down the subterranean stairways, you notice something else. Just above its point of contact with the ground, each flight of steps has a three-inch gap, a feature repeated in every handrail: the stairs are literally suspended from the building above. And at every point where workmen might be tempted to sling a ladder or lash a plank, large notices proclaim "No Rigid Links".
"That is the philosophy on which this building is based," explains its presiding acoustician Rob Harris. "There's no rigid link between any part of this building and the rest of the world. Most of it's on springs, and round the edge there are rubber joints. Where any pipe or duct crosses in from outside, there's a break in it, and a flexible joint."
This is only the latest of Harris's brainwaves. He and his friends at Arup did the insulation for Birmingham's Symphony Hall, which rests on rubber pads, and where the vibration from trains passing underneath was neutralised by insulation under the railtrack itself. He has found that springs are better than pads: if they get tired, or their tension is wrong, they can be instantly replaced. "Both these halls are incredibly quiet. You hear things you normally only catch on CDs, like the clicks and the air noise on instruments."
The exclusion of extraneous sound is child's play, however, compared with the management of sound within, and at this Harris is a past master. He was responsible for the superb acoustic of Glyndebourne's new opera house, and he's currently engaged in schemes to improve the sound in both Covent Garden and the Coliseum. But the rules governing this game - even in a new building, without architectural faits accomplis - are infinitely complex.
The key element in all his calculations is reverberation time, which is controlled by two things: the internal volume of the hall, and its degree of sound-absorption (people in seats are the principal sound-absorbers). Since this latter element - assuming reasonable houses - remains constant, the former becomes the crucial variable. To get his requisite two seconds' reverberation time, Harris has had to budget for 10 cubic metres of air per seat.
But all this depends on a third element: the shape of the hall. "It's very important," he says, "that a hall should not be too wide. A lot of the sound should be reflected off the sides." The perfect shape for a concert hall - instinctively realised in Germany and Austria in the 19th century - is therefore the shoebox, with a balcony all round. That is why the fan-shaped Barbican has such a weak acoustic, why the Albert Hall's is so irredeemably hopeless, and why the expensive tinkering now going on at the Festival Hall (too wide and shallow) may still not solve its acoustic problems. It's also why, in an opera house, you often get the best sound in the cheapest seats, up at the top in the gods.
So why is the Bridgewater not a shoebox? "It would have been, if it had only had 1,500 seats. But with 2,500, it would have got so long that the stage would have been out of sight for people at the back." But there is, he says, another classic shape: the "vineyard", as in St David's Hall in Cardiff - where the seats are grouped in blocks, and divided by walls that provide the requisite "early" reflection. The Bridgewater is a synthesis of these two forms.
It's when you try to chart the movement of sound that things get tricky, partly because sound is so hard to imagine. "You think of it first as beams of light," says Harris. "That works well with visual types like architects, but if you persist in thinking of it that way, things start to go wrong, because the analogy is only an approximation. We also talk in terms of `cue-ball reflection'." And he outlines the trajectory of an imaginary billiard ball, bouncing off the walls, balconies, and ceiling.
He and his colleagues began with a minute 1/100th scale model, which they fitted out with foil; when they fired laser beams they could see where the reflections were going, and could adjust the surfaces accordingly. Then they built an acoustic model at 1/50th scale, filled the tiny seats with tiny people, clad the surfaces with material that absorbed sound 50 times as fast as real-life material would, and fired a tiny spark at 50 times the frequency of a normal gunshot. They picked up its reverberations with miniature microphones.
Then they fired a real gun in the real chamber, with mikes all round to measure the rates at which sound developed and decayed. Finally they did the same tests in a computer simulation. "At that point," says Harris, "you have to use your judgement which to believe, because they don't always agree."
In the resulting piece of architecture, a lot of features that look like "design" are in fact subtle acoustic wheezes. The seats at the sides are backed by wooden panels with interestingly faceted surfaces, and the rims of the balcony have what look like art deco scorings. The concrete roof beams have a sound-diffusing shape, and the angular glass canopies that can be brought down low over the players' heads are "ensemble reflectors", designed to let them "hear" each other. (One of the musicians' biggest gripes at the Festival Hall is that this is not possible.)
Harris says he has been schooled through his job to listen not to the orchestra but to the hall. Now it's done, what does he hear? "Quite a loud hall, and quite a reverberant one. Not the over-mellow sound many older halls have, and a much better bass than the Barbican or the Festival Hall." So there.
Much of what goes on inside this hall, however, will closely mirror South Bank policies. Its underlying philosophy will be that of a "people's palace", with the public welcomed in for snacks and free lunchtime concerts. Through comedy events, and with a series of late-night jazz concerts under the direction of Joanna MacGregor, it will join economic battle with Manchester's club scene. When Bridgewater's chief executive Victoria Gregory describes her concert hall as a "modern-day cathedral", she has a pretty ecumenical religion in mind.
But the economic basis on which she plans to operate is unique, because Bridgewater has no direct public subsidy. It's run by a partnership called Hallogen, neatly conflating the long-established Halle Concerts Society with Ogden Entertainment Services, the world's biggest manager of venues (including Manchester's new 19,000-seat arena). Manchester City Council had been losing money on the Halle's old base at the Free Trade Hall, and it decided to solve the problem by giving the Bridgewater Hall outright to Hallogen on condition that it would be self-financing, and would impose no financial burden on the people of Manchester. Gregory must now run it on a "break-even or better" basis.
"I can't say yet if it will work," she admits cautiously. But she's making a sensible business plan, in which sell-out evenings of Eddie Izzard will compensate for sparsely attended concerts by visiting pianists. School prize-givings and public meetings - the sort of thing that kept the old Free Trade Hall busy - will be part of the regular agenda. "We wanted to combat any idea that this was going to be just another building for toffs."
Gregory claims to have tapped into a huge new pool of potential concert subscribers, though here, too, she is not pitching her hopes over-high. "People are much more impulsive than they were 30 years ago - they don't plan their evenings months ahead. The problem in this respect is the orchestras, which have become a dependent culture. They still feel people ought to come and listen to them - but there's no ought about it. This is a problem with British orchestras in general: in their private lives they expect to choose between one restaurant and another, but they can't yet see that this same principle applies to concerts. Classical music has got to be served up as smoothly as any other entertainment.'
Despite this bracing realism, she's bullish about her hall's future standing. "It's going to be one of those buildings of which people say: if you haven't played it, you haven't made it." And in the light of the opening season, the claim seems reasonable: Barenboim, Galway, Terfel, Brendel, Perahia, Glennie, Midori, Bartoli, Pletnev and the Russian National Orchestra - with Kent Nagano and the Halle as resident band.
Going round the building, one is struck by its elegant airiness, by the big vistas that open on every side. It contains (of course!) some large pieces of new "public art", one of which - a huge stream of pastel-coloured cardboard shapes - looks as if it may age tattily. Never mind, it's still a world away from the tackiness of the Barbican's gift-shop revamp.
From the windows you look out over the first piece of new canal-building Manchester has seen for 200 years: narrow-boats will moor here. This, says Gregory proudly, is the only British concert hall to have a harbourmaster's office attached. But there's one small problem; the calm surface of the canal is clogged with floating refuse. It's cleared every day, but the stuff keeps on collecting, and she can't understand why. The movement of water is as unpredictable as the movement of sound-waves: maybe it's time to call in Rob Harris's marine equivalent.
n Opening concert: Kent Nagano conducts the Halle Orchestra and Choir, with Thomas Allen (baritone), in a George Benjamin premiere, Elgar's `Enigma Variations' and Walton's `Belshazzar's Feast', 7.30pm Wednesday. Booking: 0161-907 9000Reuse content