AIR CONDITIONING Problem solving - noise The Institute of Refrigeration (IOR) discusses how to tackle excessive noise. T
he Institute of Refrigeration’s RACHP EngTech Section has recently been discussing the challenges of noise and air conditioning. This occasionally comes up with customers or neighbours concerned about the increasing number of units outside and the related increase in decibel levels. To help give technicians some pointers on how to address (or avoid) excessive noise, the Section has provided a checklist below.
It is important to note that sound pressure/level is always given at a specifi c distance and that sound power is always stated as a fi xed value. RACHP equipment sound levels are generally between 40-60 decibels at the most. A quiet air conditioner would have a sound level below 40 decibels. As part of the planning process, an engineer may be asked to carry out a noise survey to assess the noise impact depending on the site location. In this case, external plant or machinery may need an acoustic assessment by an acoustics specialist in line with British Standard 4142 (BS 4142:2014), this might apply to condenser units, heat pumps or air conditioning units. The Noise at Work Regulations also may apply. You should always consult the relevant planning authority for specifi c advice as part of a site survey.
Checklist
Some of the questions technicians and installers should consider before installing a unit: ■ Can the unit be set up further away? Sound pressure goes down with distance – double the distance to reduce the sound by -6dB
■ Are there walls nearby? Sound pressure will increase with refl ecting walls. Each hard, refl ecting wall will increase the sound level by +3dB.
■ How many units are required? Sound pressure increases with the number of noise sources. Double the number of sources and the sound level will increase by +3dB.
■ What is the direction of the fans? The main sound trans- mission is usually from the fan side of the condensing unit. It is therefore advisable to turn the fan side away from sensitive areas.
■ Can you make use of the cooler hours? Reducing fan speed at night is a great way to address noise reduction, as reducing fan speed during cooler times (like night-time) will reduce sound levels.
■ Have you considered using acoustic enclosures? As long as ventilation is taken into consideration, special acoustic enclosures can be used for noise reduction.
20 September 2024 •
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