By Steve Smith: Market Development Manager (Knauf Insulation Northern Europe)
The importance of sound design and why we should design for the people who live in and use our buildings and not to just meet the minimum requirements.
I realised the importance of sound design in buildings five years ago – on New Years Day 2010. I remember it as if it were yesterday. I remember it because it was the day my father suffered a sudden heart attack. After a number of hours of treatment, surgery and amazing care from paramedics and surgeons, his heart was taken out of arrest and began recovery in Liverpool’s Heart and Chest Hospital.
There were two things I noticed when visiting him during his four week recovery. The first was the amazing dedication and care of the excellent staff at the hospital. The second was the constant noise of beeping machines, clunking and clanging sounds on hard surfaces, and the ongoing background noise of chatter between nurses, doctors, patients and visitors. It was then that my father said to me something I will always remember:
“How am I supposed to sleep with this level of noise? How am I supposed to recover if I can’t sleep“.
Biology dictates that our bodies need sleep to allow us to recover when we are ill. For hospital patients to get the sleep they need, the World Health Organisation recommend that sound levels should not exceed 30db(A) for prolonged periods. I was sure that the noise level in the ward where my father was recovering must be far above this.
Research into the noise levels of a number of other similar Intensive Care Units suggest that I was almost certainly correct in my presumption. Of the hospitals monitored, average sound levels exceeded 45dB(A) 100% of the time. For over 50% of the time the sound level was between 52 and 59dB(A). And worst of all, peak levels of above 85dB(A) occurred with patients being disturbed at least once every 7 to 16 minutes of every hour overnight! [i] To put that into context; 85dB(A) is about the sound level you would hear if you were standing on the kerbside of a busy road, or about the same sound level as a loud alarm clock. Every 7 to 16 minutes. I’m not surprised my father found it difficult to sleep!
And it’s not just our hospitals where sound levels can be causing problems.
Five years on and my father’s recovered and happy to have three grandchildren. This means I’m taking a keen interest in schools and classroom design as I’m eager to understand the impact noise levels might be having on my children’s education.
Children need a quiet environment if they are to learn effectively. Research has shown that in noisy classrooms, children can fall behind due to reduced ability to concentrate. [ii] Noise negatively affects a child’s ability to keep attention, especially when comprehending more difficult sentences.
A similar research study showed that the average sound level in occupied classrooms was 72dB(A). [iii] Not a maximum sound level – an average sound level! Meaning that peak levels would exceed this on regular occurrences. Normal speech is generally accepted to be around 60-65dB(A) [iv] so 72dB(A) would be similar to a louder than normal conversation. This may not seem too strenuous – but when it is sustained over the duration of a school day with sound levels regularly peaking above this, it makes it difficult for children to concentrate, and difficult for teachers to teach.
Research in Germany showed that the heart rate of teachers is directly linked to noise 9. [v] More noise leads to higher heart rates. Higher heart rates lead to more stress. More stress leads to increased health problems.
If you’re reading this at work, you could be subjected to excessive noise at this very moment. I see open plan workplaces at every company I visit, including every architects practice I’ve ever visited. I expect the theory is that open plan offices are more cost effective than closed offices and provide more opportunity for collaboration between workers. This is not what the research shows.
A study published in the British Journal of Psychology showed that if you can hear someone talking while you’re reading or writing, your productivity dips by up to 66%. [vi] Have a good listen now. Can you hear other people talking? Is it distracting? Does it cause you to re-read some sentences? I know I often struggle like this when I’m trying to read an in-depth article or piece of literature if there are distracting noise levels present.
Similarly, a US study of over 40,000 office workers in over 300 separate offices showed there was no evidence that open plan offices offer benefits over closed alternatives. [vii] Indeed, employees working in open plan offices complained that the biggest issue with open-plan offices was sound privacy.
A 2005 report by the UK Commission for Architecture & the Built Environment found that a well-designed, employee-friendly office environment can boost productivity by as much as a quarter. A well designed environment which provides quiet workplaces to allow employees to concentrate without distraction.
And where do we spend most of our time?
In our homes.
Of all noise complaints to local authorities in 2012/13, 75% were residential complaints. Complaints about noise from traffic or aircraft getting in from outside, or complaints about noise caused by neighbours getting through separating walls.
The World Health Organisation estimate that a quarter of a million in the UK suffer from levels of noise, from traffic and aircraft to a level considered a serious annoyance in both the day and the evening.
Our homes should arguably protect us from this noise and give us somewhere to relax in a quiet environment.
Recent NHBC statistics would lead us to believe that it is getting better though. Between 2004 and 2010, there was a 39% reduction in noise complaints. You know what they say about statistics however! If you look at attached homes this reduction is clear to see. And it can be explained when you understand that Approved Document E (Resistance to the Passage of Sound) was added to the Building Regulations in 1992, and Robust Details was set up in 2004, to legislate and monitor sound design respectively. Looking at detached homes though (not covered by Robust Details) it is clear that the same reduction over the same period is not evident.
So why the reference to Vincent Van Gogh?
All of this is the reason I ask whether designers are designing for Vincent Van Gogh – a renowned artist famous for his visual works of art, but maybe more famous for slicing off his own ear. It would seem that Van Gogh placed more importance on how things looked and less importance on how things sounded.
It doesn’t have to be like this though. Great sound environments can be, and are being designed already. Take the Bridgewater Hall in Manchester as an example. Some of the greatest musical artists in the world have played at the Hall and remark that its acoustics are amongst the best they’ve experienced. A remarkable feat considering it’s location – a stone’s throw from Manchester Central Exhibition Centre, 20 yards from a metrolink tram stop and next to one of the major roads leading into Manchester City Centre. The hall uses a number of clever design aspects including use of curved shapes and absorbent materials inside the hall, and being located on 280 sets of steel springs to isolate it from the immediate surroundings to prevent vibrations and sound transfer.
So what can we learn from buildings such as Bridgewater Hall and what can designers do to improve the sound design of buildings?
Designing for sound
There are many factors to consider that will have an impact of the sound environment of the building:
- The location of the site – e.g. how close is the site to major roads and flight paths?
- What is the size of the building being designed?
- How will the building layout be designed? – remember the warning about open plan offices!
- What materials will be used in the construction of the building?
- What equipment will be used in the use of the building?
- Who will use the building? – people can be the biggest variable
At Knauf Insulation, we recommend the use of absorbent materials such as glass mineral wool or rock mineral wool, wherever possible, to absorb sound and improve sound insulation.
The fluctuations of air molecules which form sound waves move into the body of the mineral wool. Friction between the air particles and the narrow airways of the wool causes sound energy to be dissipated as heat, reducing the level of sound moving through a building structure.
When looking at internal walls and floors it is often worth investigating providing sound insulation to all walls and floors, rather than just those identified in Approved Document E. Additional cost can often be minimal whilst long term benefits and sound comfort for occupants can be huge.
But one of the biggest areas which can be used to provide sound insulation is the external building envelope. Thermal insulation is required to prevent heat loss to meet the requirements of Approved Document L. Using an absorbant material which provides acoustic performance as well as thermal performance is the ultimate win win.
Designers are already realising this and using the external envelope to provide acoustic performance. When Birmingham Airport built a new air traffic control tower, mineral wool was used within the rainscreen cladding system. This was to provide a high level of sound insulation, as well as thermal insulation to ensure sound within the tower was maintained at a level which allows the air traffic controllers to concentrate and perform their job effectively. I know when I’m flying into an airport I want to know that the controllers are concentrating to their full potential and aren’t distracted by the high levels of unwanted noise from the incoming air traffic!
Dublin Airport used a similar approach and utilised a standing seam roof design incorporating mineral wool to provide the combined acoustic and thermal performance. These systems can provide sound insulation of around 46dB Rw . This means if the noise level outside is 96dB (A) – the typical sound level of a Boeing 767 coming into land at a distance of 1 nautical mile – the sound inside would be reduced to 50dB(A) – quieter than a normal conversation. Birmingham University used mineral wool insulation within their rainscreen cladding system so that students could concentrate fully. And there are many more designers identifying the value in good sound design.
Why design for sound then?
After all, good sound insulation can provide many benefits over and above compliance with the minimum performance requirements stipulated by the Building Regulations.
There are extra credits which can be claimed in BREEAM for providing a better level of sound performance than the minimum requirements.
Designers and architects practices who are already designing for sound are realising that they can use it as a point of differentiation, in a market where differentiation can mean the difference between survival and business success.
But more than all of this good, sound design can mean that we live more comfortably in our homes, that our children learn better, that our teachers teach more effectively and with less stress, that we perform better in our workplaces, and that our families recover more quickly in our hospitals.
It’s time to start designing for sound. It’s time to start designing for the people who use our buildings.