It's fair to say that Australia's brutal summer seasons make air conditioning more of a neccesity than a luxury, and a properly working air conditioning system is particularly important for keeping your bedroom cool and comfortable enough to sleep in at night. However, air conditioners can also create a substantial amount of noise during operation, so the homeowner seeking to install air conditioning in their bedroom needs to strike a careful balance between the effectiveness of their air conditioner and the amount of noise it generates.
As a a general rule, a more powerful air conditioner will create more noise -- however, some types of air conditioner create far more noise than others, so choosing the right configuration will allow you to install an efficient, powerful air conditioner that won't keep you away with buzzing and droning. The following types of air conditioner can all be used effectively in bedroom settings:
Central air conditioning
If your home already has a central air conditioning system installed, extending it to your bedroom is the easiest and most effective option.
The substantial condenser units that power these conditioners can actually be quite loud; however, because they are usually installed in locations reasonably far away from your bedroom (such as garages, closets or sheltered outdoor locations, the noise from your condenser generally does not reach the bedroom. The most amount of noise you can expect from a properly installed central air system is a gentle gusting noise as the cooled air exits your bedroom vent, at decibel levels far too low to disrupt sound sleep.
Ductless split system air conditioning
If you are not lucky enough to have a central air conditioning installed in your home, going to the time and substantial expense of having one installed just to cool your bedroom might not make much sense. For these situations, an efficient, quiet single-room air conditioner is more suitable, and ductless split system air conditioners are practically ideal.
These units consist of a condenser unit located outdoors, which feeds cool air through a small pipe that runs through your exterior wall and connects to a wall or ceiling-mounted ventilation unit. The highly effective sound insulation provided by the exterior wall muffles all but the loudest and most poorly-maintained condenser units, allowing you to choose a powerful condenser unit that can quickly cool the largest of bedrooms.
Although these units are more expensive than portable or window-mounted air conditioners (largely because of the modest amount of wall modification required to install them), they are considerably cheaper than central air units, and installing one may even be cheaper than extending the ducting of an existing central air system. They only have one fatal weakness; they cannot be used in bedrooms that don't adjoin to an exterior wall.
Portable air conditioners
If you are on a tight budget and cannot afford to install a permanent air conditioning unit in your bedroom, opting for a portable air conditioner might be your best option.
These all-in-one units contain their own condensers, and therefore make considerably noise than central or ductless systems. However, because these conditioners are intended to be transported frequently, they are built to withstand a fair amount of bumps and scrapes; this generally results in a thicker, more insulated casing than that found on a window-mounted air conditioner, which subsequently muffles the noise of the condenser and internal fans much more effectively.
If your budget can stretch a little further, consider choosing a portable air conditioner intended for commercial use. These units are designed to run as quietly as possible to prevent distractions when used in office environments, and some manufacturers offer models with generated noise levels comparable to a small split system air conditioner.