In today’s market, ventilation products often carry names that suggest near-silent operation, incorporating adjectives such as “Silent,” “Quiet,” and “Whisper.” However, the question remains: how quiet are these extractor fans in real-world conditions?

The Reality of Extractor Fan Noise

Manufacturers strategically name products to emphasize appealing attributes, a tactic used in marketing across many industries. When it comes to extractor fans, two key factors influence purchasing decisions: performance (the power and efficiency of air extraction) and noise levels (operational sound output).

As mechanical devices with moving components, extractor fans inherently generate some degree of noise. This noise originates from both the motor and the airflow itself, which encounters resistance as it moves through grilles, impellers, and ducting.

Why Are Fans Marketed as “Silent” or “Quiet”?

Despite the unavoidable generation of sound, modern extractor fans are significantly quieter than older models due to advancements in engineering. Innovations such as low-friction bearings, brushless motors, aerodynamically optimized impeller blades, and refined grille designs have collectively reduced operational noise.

It is worth noting, however, that even older, noisier models have been labeled with similar descriptors, creating an ongoing cycle where each generation of fans is marketed as the quietest yet—until further advancements introduce even quieter options.

Evaluating Noise Levels: Decibel Ratings and Perceived Loudness

Each extractor fan is assigned a noise level measured in decibels (dB). Understanding decibels can be complex due to their logarithmic nature. A 10dB increase effectively doubles the perceived loudness. For instance, the difference between 20dB and 30dB is comparable to the contrast between rustling leaves and a whisper, whereas a jump from 90dB to 100dB equates to the difference between a hairdryer and a helicopter.

Most domestic extractor fans operate below 50dB, whereas commercial-grade units may exceed this threshold. However, the published noise levels are typically measured from three meters away in a controlled environment, without additional factors such as ducting or wall-mounted resonance. Consequently, actual perceived noise may differ based on installation conditions.

Installation Factors Affecting Noise Perception

Beyond the technical specifications, installation plays a critical role in determining the noise level experienced in everyday use. Below, we examine two common installation scenarios and their impact on noise levels.

1. Inline Fan Installation (Loft Mounted)

Inline fans are commonly installed within a loft space, with an internal grille placed in the bathroom ceiling. Ducting connects the grille to the inline fan, which then expels air via more ducting to an external vent positioned in a soffit, gable wall, or roof.

Once ducting is attached, noise levels often increase due to airflow resistance. Friction within the ducting generates sound, and sound waves reflecting off internal surfaces of the building can further amplify perceived noise. The length of ducting and number of bends impact this effect with each 90-degree bend adding resistance equivalent to an additional metre of duct length.

Methods to Reduce Noise in Inline Installations:

• Use Solid Ducting Where Possible – Smooth interiors minimize friction and reduce noise.
• Stretch Flexible Ducting as taut as possible – This prevents airflow turbulence caused by peaks and troughs within the duct.
• Select Low-Resistance Grilles – Internal grilles should have minimal airflow obstruction to prevent unnecessary noise.
• Utilize Low-Speed Settings – Many inline fans have variable speed controls, allowing for quieter operation while maintaining efficient extraction rates.
• Mount the Fan on Anti-Vibration Pads – These reduce vibration transfer to surrounding structures.

2. Through-the-Wall Fan Installation

This type of installation involves a direct ducting path through a wall, connecting to an external grille. Since there is no extended ducting, fewer factors contribute to additional noise.

One key consideration is the choice of the external vent. Older designs included fly screens to prevent insects from entering; however, these mesh screens often accumulate dust and debris, restricting airflow and forcing the motor to work harder, which increases noise output. Modern grilles are designed to minimize resistance while preventing backdrafts, helping to optimize performance and noise levels.

Again, the use of solid ducting for a through-the-wall installation is ideal for the same reason of minimising noise but also as it is a far simpler installation than fiddling with flexible ducting through walls.

Practical Solutions for Minimizing Noise

For those sensitive to noise, various solutions can help mitigate disturbances:

Use a Humidistat-Controlled Fan – Instead of activating with the light switch, a humidistat-operated fan turns on only when humidity levels rise, such as during a shower.

Ensure Adequate Replacement Airflow – Blocked airflow increases motor strain and noise, similar to a vacuum cleaner with a blocked hose.

Consider Placement Carefully – Positioning a fan too close to an occupied space may result in greater perceived noise.

It is also worth looking at constant-running dMEV fans instead of standard intermittent fans for through-the-wall installs and in some cases, ceiling-mounted fans. It may seem counter-intuitive to suggest a fan that is constantly running to help minimise sound levels, but whilst on trickle speeds, these units are often so quiet that they are unnoticeable.

There is also the benefit that they don't need to run as fast as traditional intermittent units when boosted, as the cumulative effect of the constant trickle and intermittent boosted speeds will often give better protection from humidity than a more powerful intermittent unit.

Finally, some dMEV units give you control over the speed settings of the trickle and boost speeds, which allow you to find the perfect compromise between function and running noise.

The Tornado ST100DMEVS, ST100DMEVHT, Vent Axia Svara and PureAir Sense models all allow you to control and set both of these speeds whereas the Monsoon DMEVR100HT gives access to adjusting the trickle speed while utilising an intelligent humidity sensor to only boost the speed incrementally inline with the humidity rise to help minimise noise and energy use and the Envirovent Silent Dual incorporates three running speed - low trickle, medium boost (activated via motion control when you walk into the bathroom) and a high boost triggered by humidity.

The Balance Between Noise and Functionality

While no extractor fan operates in complete silence, modern units are considerably quieter than older models. It is important to balance the desire for low noise levels with the necessity of maintaining indoor air quality. A well-functioning extractor fan prevents damp, mold, and poor air circulation, ultimately benefiting both the building structure and its occupants.

By selecting the right fan, optimizing installation, and implementing noise-reducing measures, homeowners can enjoy effective ventilation with minimal disruption to their living environment.