Urban living – a growing trend in all our cities as new and converted apartment blocks and warehouses continue to come onto the market – has its drawbacks, as many urban dwellers have found. Significant among these is the growth in what the World Health Organisation (WHO) calls ‘community’ or ‘environmental’ noise, which includes external noise such as road, rail and air traffic; industrial noise, construction and public works noise; and neighbourhood noise, such as kids playing soccer in the street and shop shutters being dropped or raised. Then there are the many indoor noises, such as ventilation systems (air conditioners and fans are seldom silent), office machines (increasingly a part of home life), home appliances (especially washing machines) and neighbours (from the sounds of loud TVs and crying babies to creaking beds, all transmitted through ceilings, oors, walls and windows).

Faced with all this, you might wonder why people choose to live in cities at all – particularly in apartments converted from office blocks, industrial warehouses or factories, none of which were ever designed for residential use in the first place. However, properly converted, there is no reason why these new living spaces cannot be peaceful ones as well. The trick here is to understand the acoustic issues and then design and build, both holistically and speci cally, to minimise them.

The technical term for reducing noise is noise mitigation, namely the measures that can be taken to lessen the impact of noise. A word of caution: some buildings simply cannot be insulated effectively against certain types of noise, such as tra-ffic, discos and restaurants. Acoustical engineer Adrian Jongens tells stories of loft-owning clients with huge, beautiful yet poorly fitted arched windows that let in exterior noise, and roofs that magnify the noise coming from the immediate neighbourhood. It is indeed possible, in the caser of a loft, to build a sound-insulated sleep capsule with its own ventilation system, but you can imagine for yourself the cost that’s involved in such a drastic step, let alone the inconvenience. Best to avoid that situation before you buy.

As Adrian says, it is important to re-look the age-old adage about purchasing a home – location, location, location – which does not just refer to the neighbourhood, views or accessibility to shops and work, but also to a home’s distance from the source of road traffic noise, considered to be among the worst pollutants on the planet. You might, if you are at home during the day, get used to the ambient noise created by the sounds of the city – cars hooting, lorries braking, workers shouting, trains departing, ’planes coming in to land – but at night it’s a diffierent story. Quality sleep is something we cannot do without. Sleep disturbance has been proven to increase fatigue, decrease performance, raise stress levels, depress wellbeing and change behaviour (not for the better, either). WHO guidelines indicate that average daily exposure to noise greater than 65 decibels (which is high, but perfectly possible on occasion in a dense urban area) can increase aggression in those predisposed to violence – not a nice thought.

So, an investigation of noise levels in the area you are considering is well worth the effort. The WHO Guidelines on Community Noise and the SA National Standards both draw a line at 55 decibels for acceptable external noise in residential areas, and suggest a maximum 30 decibels for bedrooms. By way of comparison, most big concerts subject you to 100 decibels. (Incidentally, the guidelines recommend that you only attend big concerts four times a year for no longer than four hours at a time, if you want to protect your hearing.)

There are various types of noise: external and internal, airborne and impact. Without entering too complex a discussion on frequencies, wavelengths and sound diffraction, re ection and reverberation, the key issue here is that sound is both heard and felt, and it is often the sounds that are transmitted through a building that are the most insidious. Back to the sleep story – wind rattles your windows, an industrial lift shaft vibrates throughout a loftapartment building, a palm tree knocks against your roof, the low-frequency bass from a disco in the basement of your apartment block travels through the building and uses your walls as a loudspeaker. You might eventually manage to fall asleep amidst all this noise, but the quality of your sleep will most likely be poor.

So, what are the solutions to these urban realities? For keeping out exterior noise, architectural elements such as sound-insulating glazing – laminated glass in heavy frames with airtight closures – and roof material have been known to yield a modicum of success. Rain on corrugated iron? Forget the romance – restless sleep is the result. Seal any gaps between windows, walls, oors, doors and ceilings – a process known as caulking – and carefully design any other areas that require wall penetration, such as post slots, air conditioner vents and air bricks. And, of course, this is all much cheaper if factored in from the start of the design process. Making a badly converted building sound-tight after the fact is far more complicated and costly – if it’s possible at all – than doing it at the design stage.

This applies especially to the reduction of internally generated noise. Airborne and impact-generated noise travels through walls and floors, so employing the best available quieting technology and design – for example, shock or oat-mounting kitchens and bathrooms where home appliances, such as washing machines, can set up serious vibrations – can sometimes prevent noise transmission. You can specify quieter appliances as well – they cost more, but generally they do a better job. Vibration can also be created by pool pumps, elevators, plumbing and air conditioning systems. In apartment blocks, generators and machine-plant rooms can also transmit sounds throughout a building if not properly insulated. If you discover that only after you’ve moved in, it’s usually too late to remedy the situation – rather tart up your apartment and move.

Ultimately, the challenges of noise mitigation are many. There is no substitute for thorough research into the environmental noise factors of your new home. It may be worth spending the money on an acoustical engineer to check it out. Prevention is, after all, better than cure.