What is acoustic ventilation and how does it work?

What is acoustic ventilation and how does it work?

By Ruth MacEachern

Product Manager

Modern domestic mechanical ventilation systems offer a wide range of environmental and financial benefits; however, it is important to remember that the primary goal of any home ventilation system is to improve the indoor air quality and the comfort experience inside the home. An overview of changing building regulations and their positive impact on the indoor environment can be found here, however, all of these benefits can quickly become overshadowed if home comforts are disrupted by a noisy ventilation system. In our previous blog article we addressed the current regulatory requirements concerning ventilation acoustics and how to demonstrate compliance. In this article we will turn our focus to a number of fundamental questions: “What is acoustic ventilation?”, “How does acoustic ventilation work?” and “Which acoustic solutions are available?”. Continue reading to discover which products you can purchase with a view to ensuring compliance with the guidelines discussed in our previous article, and for insight into what actually goes on within an acoustic ventilation system.

Back to basics: cut out those negative vibes

When considering how acoustic ventilation works, it is worth remembering how sound travels in the first place. Whether it’s your vocal cords, a loudspeaker , or some poorly fitted ducting, noise travels from one space to another when a vibrating object causes the air around it to vibrate. This vibrating air then travels into the recipient’s ears, causing their eardrums to vibrate, which is then interpreted as sound by the brain. As such, acoustic ventilation and noise attenuation systems are essentially means by which to eradicate or reduce vibration as much as possible, preventing this vibrating air from reaching inhabited spaces within the home. When designing a ventilation system with a focus on acoustics and attenuation,  it is important to begin right at the source with the selection of an appropriately sized ventilation unit and  correct installation on a fixed, solid base. This then  continues along the ducting system to the vents located throughout the home; the points at which the ventilated air is released into the living environment. Among the many considerations and compliance factors that must be weighed up when installing a mechanical ventilation system (a summary of which can be found here), it is therefore vitally important that noise emissions are taken into account from the early planning stages. Once you have selected and correctly installed the system that is most appropriate for your building, there are a number of available solutions by which to attenuate noise, and cut out those negative vibes…

Available solutions and how they function

1. Acoustic air vents: these include vents fitted with a sound-absorbing lining. Many models also feature an adjustable grille, which can reduce noise by up to 50 dB when fully closed.

2. Ventilation duct silencers/attenuators: made of galvanized, aluminium, stainless steel or plastics, duct silencers may likewise by fitted with a non-compatible mineral wool lining to absorb sound vibrations, or a (round) pod or vertical baffle to improve attenuation.

3. Flexible ducting: sections of ducting that are causing surrounding fixtures to vibrate, thus generating noise,  could be replaced with flexible ducting, though this should be kept to a minimum due to high resistance levels.   Flexible ducting is  often made from thermally insulating aluminium, or can be wrapped in an additional insulating material, thus simultaneously improving the thermal efficiency of your ventilation system (check out this article for an overview of the benefits of an energy-efficient ventilation system).

4. Rigid duct silencers: for installations where flexible ducting is not possible, for example in high flow rate installations, rigid duct silencers/attenuators are also available. These are often made of plastic.

5. Acoustic trickle vents: noise-reducing acoustic vents are also available for external windows, facilitating the flow of air in and out of a building, while helping to prevent the ingress of external noise.

Additional tips to help cut noise emissions from your MEV or MVHR system

• Use ducting with as large a diameter as possible – this will result in the same quantity of ventilated air reaching the respective rooms, but with a slow flow rate, thus reducing noise.
• Ensure that the system has been designed and the airflows have been correctly commissioned to avoid the system running at excessive capacity.
• Advise those purchasing the home to regularly maintain and clean their mechanical ventilation system. Blocked filters and vents mean that the system will have to operate at a higher speed in order to perform at the required level. A clean system is an efficient system, and an efficient system is generally much quieter.
• When commissioning, be sure to carry out appropriate noise emission tests at all points of the installation, using the appropriate technical equipment – call in an expert if necessary.

A quiet and efficient mechanical ventilation system is a major selling point

MVHR systems have been proven to reduce carbon emissions, cut heating bills, improve indoor air quality, and offer a wide range of health benefits, such as the alleviation of chronic respiratory conditions such as asthma, and the reduction of allergens in the home (e.g. pollen and dust). Provided the system is correctly installed so as to avoid unnecessary noise emissions, this represents a major selling point in favour of a  new build. If you require assistance or advice on the selection and installation of a quiet and efficient system, contact the experts at EnviroVent