Hear, here: designing sonically superb acoustic spaces
Image credit: Maxim Schulz
In search of acoustic perfection – and, occasionally, imperfection.
On the island of Malta, there is a 5,000-year-old Bronze Age underground temple called the Hypogeum. Carved out of solid limestone, it has three storeys, the deepest of which, known as the Oracle Room, is decorated with red ochre spirals.
This is a resonance chamber: a space that exhibits a dramatic intensification of sound, produced by sympathetic vibration at a particular tone. The resonance in the Hypogeum occurs at 110Hz – a low-frequency tone with a waveform the same length as the chamber. In other words, the dimensions of the space are an exact multiple of the wavelength of that frequency. This was almost certainly not a coincidence.
These ancient humans had tapped into complex acoustic behaviour, using the chamber’s reflections and sound waves in sync to create a natural amplification known as constructive interference, or standing waves. It’s as if the 110Hz tone is stuck on a feedback loop.
Modern neuroscientists have demonstrated that experiencing this intense, hypnotic, reverberating sound affects the prefrontal cortex of the brain, creating a functioning asymmetry similar to the feelings of transcendence achieved through deep meditation. Prehistoric man had created his own immersive temple of sound in a quest for spiritual enlightenment.
Sound is important to us. The human ear enjoys three times more neural connections to the brain than the eye. We can detect a vibrating molecule as slow as 20 beats per second – i.e. 20Hz – all the way up to 20,000Hz. This equates to 10 octaves of sound and we’re all surprisingly adept at discerning even very subtle variations in soundwaves, both in pitch and amplitude.
We’ve all experienced the pleasing change in the tone of our voice when we walk under a stone bridge or the effect on the sound of our footsteps as we walk through a concrete tunnel. This is natural reverberation at play. The soundwaves are bouncing off the walls, these early reflections combining with the original waveform to create the sound we receive at each ear.
Soundwaves travel at a known speed, so are predictable, and are a branch of physics dealing with frequency, wavelength and amplitude. This means soundwaves can be defined by mathematics, which in turn means we can understand them and control their characteristics and behaviour.
The waves are affected by reflection, refraction, diffraction and absorption, and determined by the mass of an object they encounter; the composite material of said object; even the air temperature. In designing acoustics for a space, the challenge is to get these waves to behave.
Man’s appreciation of acoustics has had an ongoing effect on architecture. Churches and cathedrals are one example, as medieval builders harnessed the acoustical properties of their holy designs to produce a dense, lush reverberating effect, an echo sometimes lasting 10 seconds or more. Perfect for organ recitals and choral music.
As classical music evolved, so buildings also changed to better showcase it. There are certain halls around the world that are renowned for having superb acoustics. These are places where musicians love to perform and audiences love to listen.
Received wisdom has it that London lacks a world-class concert hall and that its existing halls all present unique acoustic challenges: the Royal Festival Hall is too ‘dead sounding’ (the designers miscalculated the absorption rate of the audience, thus drastically shortening the reverb time); the Barbican is the wrong shape (cinema-style fan; few side reflections) and the Royal Albert Hall is simply too big (5,000 seats).
A campaign to build a new world-beating, acoustically optimised concert hall in London has been rumbling on for a decade, as successive governments flip-flop on funding (latest cost projection: £288m). Current thinking is that the site of the Museum of London, south of the Barbican, could be a good spot, given the museum’s imminent move to Smithfield Market. An artist’s impression of a timber-clad spiral design was circulated last year, detailing an “acoustically perfect” 2,000-seat concert hall. The debate continues.
Yasuhisa Toyota, director of Nagata Acoustics of Tokyo and a much sought-after acoustician, has been responsible for the sound of many of the most famous concert halls built this century. He explains one of the fundamental issues: “There would be no perfect acoustics, or no place where everyone thinks the acoustics are perfect. There will be at least someone who thinks the acoustics are not optimal.”
Ironically, a 19th-century concert hall still considered to be one of the best in the world – the Musikverein in Vienna, built 1812 – was designed long before the science of acoustics was fully understood and yet sounds so fabulous that it has been both a template and sonic benchmark for hall design ever since. Danish architect Theophil Hansen based his design largely on intuition rather than scientific theory, but luckily for him – and for the concertgoers – it worked out beautifully.
The Musikverein concert hall has a relatively small rectangular shape; the ‘shoebox’ style. The narrow, tall shape provides plenty of lateral reflections. The first reflections reach the listener from the side, so the music at both ears is subtly different, as it takes longer for each reflection to reach the further ear. The sound wave is also attenuated, because the sound has to bend around the head.
The Musikverein also features rich plaster decoration and high ceilings. Sound bounces off the many planes and angles of the crenellated, gilt-edge balconies, contributing to a radiant sound that envelops the audience. That sense of ‘envelopment’ – the reverberation’s overall quality and clarity – is one of the defining characteristics of an excellent concert hall.
The UK is not without its own acoustic jewels: Birmingham’s Symphony Hall (opened 1991) is celebrated as possibly the finest-sounding hall in the country, while Sage Gateshead (2004) is a fine example of architecture (Foster & Partners) and acoustics (Arup) coming together in form and function.
The Sage illustrates the importance of due consideration being given to acoustics in building work. As Trevor Cox, professor of acoustic engineering at the University of Salford, says: “The creative and fruitful working relationship between architect and acoustic consultant is key to a good design. A common mistake is for the importance of acoustics not to be considered early enough in the design. Considering acoustics too late means the cost of good sound is likely to be more expensive.”
Recent flagship concert hall builds have wisely incorporated acoustic concerns from the beginning, as well as taking a different approach to hall shape. Both the Paris Philharmonie (2015) and the awe-inspiring Elbphilharmonie in Hamburg (2017, pictured above) were designed in the ‘vineyard’ style, where the musicians perform almost in the centre of the auditorium, with the audience surrounding them in rising, terraced rows of seats – a ‘music in the round’ design that can be traced back to Hans Scharoun’s Berlin Philharmonie (1963). Architect Scharoun noted how “people always gather in circles when listening to music informally” and built on this idea in his design. Acoustic designer Lothar Cremer broke the audience into blocks of seats, now known as vineyard terracing.
Toyota visited Berlin in the early 1980s and the “acoustical intimacy and visual intimacy” he experienced inspired him to bring this approach back to his acoustic work at Suntory Hall, Tokyo. The sense of acoustic intimacy has informed much of Toyota’s work since, notably at the Walt Disney Concert Hall in Los Angeles, designed by architect Frank Gehry, at the Philharmonie de Paris, Finland’s Helsinki Music Center and the Elbphilharmonie.
For the Hamburg hall, Toyota used advanced sound algorithms, creating coral-reef-like structures of over 10,000 sheets of acoustic gypsum fibre panels. This ingenious ‘white skin’ (pictured below) covers the surface of the walls and ceilings in the Grand Hall. In combination with an expansive reflector in the middle of the vaulted ceiling, these panels project sound into every corner of the space. They feature a total of one million ‘cells’, designed to shape the sound. When the sound hits a panel, the uneven surface either absorbs or scatters it to create a balanced reverberation across the auditorium.
Successful concert hall design is largely about finding the delicate balance between innovative architecture and world-class acoustics. As Toyota observes: “There are many other factors than acoustics to make the decision of concert hall style, which are architectural, theatrical, functional – many of them are visual”.
Technically, an acoustician will have to consider airborne sound, structure-borne sound and infrastucture noise. Both Elbphilharmonie’s Grand Hall (vineyard) and Recital Hall (shoebox) were built with double walls, where the inner wall is not connected with the outer one: instead, it rests on hundreds of large springs that shield the concert halls from the outside world (similar springs support Sage Gateshead).
“In architectural acoustics,” says Cox, “the knowledge is pretty extensive, and a lot of the problems we hear are about not applying the knowledge we have because of poor design or workmanship. You can have the best design in the world, but if it is then constructed wrong you get problems.
“This is very common, which is why people in acoustics are excited about modular off-site construction, because it is easier to get better construction in factories than at a building site.”
For Toyota, the list of essential information he requires when designing acoustic treatment is short: “Room shape and dimensions. Material, including structure behind.” From this starting point, the acoustic response of the proposed space can be calculated, studied and perfected. In this regard, Toyota highlights the crucial leap forward for acoustic design. “Computer technology changed the game,” he says. Digital tools such as building information modelling and sound analysis software have revolutionised the work.
While the pursuit of acoustic perfection remains key in designing the world’s finest performance spaces, there can also be occasions when scientifically imperfect acoustics can prove desirable. As Toyota acknowledges, “‘Good acoustics’ is a subjective term. There would still be many factors to configure ‘good acoustics’ in different ways.”
Many legendary recordings have been made in less than perfect conditions. These unusual spaces imparted their unique sonic fingerprint on recordings, which enthralled listeners. Sometimes the vibe can override the science, emanating an intangible aural aesthetic.
There is a legacy of great recordings being made with only minimal equipment in fairly unprepossessing locations. Sun Studios in Memphis, for example (which captured early rock ’n’ roll sessions by Elvis Presley, Jerry Lee Lewis and Johnny Cash, among others) had just a single live room. A converted former radiator shop, the performance space barely had any acoustic treatment – just perforated ceiling tiles – but the sound of musicians playing live in that cramped space is still sought after today.
Rudy Van Gelder started jazz label Blue Note Records in the 1950s by recording albums by Miles Davis and Theolonius Monk in his parents’ living room in Hackensack, New Jersey. ‘Hitsville USA’ was the name Berry Gordy gave to Motown’s first Detroit headquarters and studio in 1959, based in a residential house formerly used as a photographers’ studio. Down in Alabama, a former coffin showroom at the side of the Jackson Highway became Muscle Shoals Sound recording studio (pictured below), an unprepossessing concrete slab of a building owned and run by four local session musicians known as The Swampers, who had played on countless R&B hits. The Rolling Stones rocked up in December 1969 to record ‘Brown Sugar’ and ‘Wild Horses’, drawn to the place by what drummer Charlie Watts called the Studio’s “very special” atmosphere. Aretha Franklin, Wilson Pickett, Bob Dylan, Paul Simon, Elton John and many others followed the Stones down South in search of the studio’s sound.
These days, room calibration software is available to help people ‘tune the room’ wherever they are, identifying which frequencies require most attention. Using a sine wave sweep and analytical microphones, an EQ filter tailored to compensate for that room’s acoustic deficiencies can easily be created and applied to the mix. Now any room can be a ‘good room’.
The principles of acoustical science are also applied to everything from open-plan office design and buildings to the soundscape of an entire urban area, or insulating one activity from another, such as minimising the effects of noise pollution from railway lines or motorways on nearby housing. “Problems arise when not enough thought is given to the function of the building,” says Cox. “For example, if open-plan offices are used as a way to cram more people in and save money, it is a recipe for disaster. Noise is a major issue in such spaces.”
It’s also about getting a better understanding of people’s ears and how they work. Modern psychoacoustics is concerned with how humans respond to what they hear, whether that noise is annoying or transcendent. As Cox says: “Our knowledge of how the brain processes music is relatively crude, there is lots to learn about the listener.” It may have taken thousands of years, but we’re finally getting to grips with the importance of good acoustics.
Sign up to the E&T News e-mail to get great stories like this delivered to your inbox every day.