City living has many conveniences, but what it often lacks is peace and quiet. Hearing every step the upstairs neighbour takes, the piano practice of the child next door or relentless traffic outside are not conducive to the serenity we aspire to in a home. Noise is bad for our health. According to the World Health Organisation (WHO), noise can lead to a range of conditions including pain, hearing impairment, sleep disturbance, heart conditions and stress-related hormonal responses. Traffic noise alone, says the WHO, is harming the health of almost every third European. Noise reduction services are big business. In closed-door laboratories, inventors work away hoping to produce the answer to millions of city-dwellers' prayers. At universities and other institutions, acoustic engineering students are learning the art of noise abatement - skills that are in great demand as living environments become ever more crowded. A cursory glance on the internet would indicate a range of ready-made solutions. But which ones work? The first thing to do, says acoustics specialist Neil Gross, is identify which sounds are annoying, because noises are of different kinds, and so are the solutions. Gross is a director at acoustical consultants Wilkinson Murray, which has offices in Hong Kong and Sydney. In effect, people like him are 'noise-busters' who go to people's homes armed with equipment to track down the nasties. They will look, listen, poke and probe, and at the end of the exercise provide recommendations and referrals. Gross says such consultancies are not aimed at selling products. 'We provide advice for people to follow up on as they choose.' First, the consultants check the perimeter: windows and doors are the most likely suspects for letting in noise from outside. The presence of an older-style, window-mounted air conditioner is akin to hitting the jackpot. These often have gaps around the fixture, and if daylight or a breeze comes through then noise is penetrating too. Air vents or ventilation fixtures have the same acoustic drawbacks. 'The weakest point is always the holes,' says Gross. The windows themselves are next on the hit list. 'Old or poorly sealed windows can give only a 15 to 20 decibel reduction,' says Gross: they will only reduce the outside noise level by less than one-quarter. The firm would recommend improving the sealing, increasing the glass thickness, using laminated glass or secondary glazing as solutions. Secondary glazing should not be confused with double (or triple) glazing. The latter used mainly for thermal effect, and because the additional panes of glass are packed tightly together, they can have little or no extra sound-deadening effect in some situations. 'For low-frequency noise such as traffic or aircraft, double or triple glazing could actually make it worse,' says Gross. Other experts agree that a better solution is to allow as wide a gap as possible between the layers of glass, which secondary glazing achieves. However, Gross says double glazing is not always wrong. Near a railway line, the squeak of wheels on tracks is high frequency, and for this 'double glazing will work well,' he says. It's a case of different solutions for different problems. Inside the home, there might be other culprits letting in unwanted noise. While it shouldn't happen in a well-finished building, the cornices could hide a gap between the wall and the ceiling slab, which would need to be sealed. Or the kitchen or bathroom exhaust systems might be linked to those in the flat next door. Gross says what is put inside the home can make a difference as well. Stone, marble or ceramic finishes, for instance, might have visual appeal but they also make sound reverberate. Sound-absorbing soft furnishings such as carpet and rugs can help. Every bit counts, even concealing absorptive material behind artworks on the wall. In Hong Kong buildings the biggest nuisance can be the flat above, below or down the corridor. It can be a problem even if the connecting walls are built of solid concrete. In this situation, internal wall problems need to be addressed. Barrierboard, a product developed in Australia and available in Hong Kong, addresses this specific issue. Inventor Nereo Castelli, an acoustics engineer, wanted to create an effective, inexpensive, and easy to install product. It comes in the form of plasterboard panels on either side of an isolation layer made of vertically lapped polyester fibres. The panels are applied to walls using dabs of construction adhesive, or may be installed on battens on the roof. The joints are then trowelled off, leaving a plaster finish that may be painted or papered as normal. Castelli says that, once installed, it's impossible to tell Barrierboard is there. He claims that with total coverage it can reduce noise from neighbouring flats by 30 to 50 per cent. Another abatement product is by NoiseStop Systems Singapore, which offers an Asia-wide consultancy. It sells its multi-layer system of sound-absorbing sheets, which are made of compound inorganic material and attached using adhesive and screws. Acoustics consultant Ned Nelson co-invented the system. Noisy neighbours are the most common concern for people using the firm's services. 'We get called out to many flats each week for these types of problems,' says Nelson. 'Almost everyone who lives in a flat can hear their neighbour upstairs at some point.' The firm has soundproofed 500 homes in Singapore this year alone, and claims its NoiseBlock System Option 1 reduces 80 per cent or more of the noise. 'We give a guarantee on our products that if this is not the case we will come back and add more soundproofing free of charge. We have never had to do this once,' Nelson says. Some solutions may be even cheaper. The Hong Kong division of global engineering firm Scott Wilson Ltd deals with noise pollution in residential buildings and says that in some cases the Hong Kong government will pay for retrofitting double glazing in private premises where a new road project results in higher than acceptable noise levels. 'In another similar project, the government subsidised the installation of air conditioners so occupiers could close their windows to reduce noise, where previously they had used fans and open windows for ventilation,' says a company spokesman. That may be worth investigating. However, Gross of Wilkinson Murray says there is no magic bullet. 'When we choose to live in an apartment, we should expect to hear the neighbours sometimes. For anyone who is that sensitive to noise, probably the best solution is to move.'