Testing acoustic trickle vents for noise attenuation: what’s required?

When designing or refurbishing buildings in noisy environments - whether near busy roads, railway lines, or airports - adequate ventilation and effective noise control are top priorities. Acoustic trickle vents are supposed to provide both fresh air and robust noise attenuation. But how effective are they??

Why Acoustic Trickle Vents Matter

Acoustic trickle vents are supposed to provide a continuous flow of fresh air into a building while keeping windows securely closed. They are fitted to maintain healthy indoor air quality without sacrificing the acoustic integrity of the building envelope. 

This balance is especially important in:

• Urban areas exposed to constant traffic noise

• Mixed-use developments near commercial or industrial zones

• Properties located close to airports or railway line.

• Residential projects that must comply with strict local noise regulations

But do Acoustic Trickle Vents Actually Work?

Before we go any further, let’s address the obvious question:

Do acoustic trickle vents actually work?

The short answer is yes - but only when they’re properly specified, independently tested, and correctly installed.

There is a wealth of evidence - from laboratory data to on-site performance - that confirms well-designed acoustic background ventilators can meaningfully reduce sound transmission while meeting airflow requirements.

However, for many specifiers, the real challenge is working out how to interpret the technical data and ensure the selected product will perform as expected in real-world conditions.

So, how do you make sense of the acoustic performance claims and test results manufacturers present? And how can you be confident these reflect what will actually happen once the product is installed?

Regulatory and Testing Standards

Acoustic trickle vents are typically assessed for sound insulation performance under controlled laboratory conditions.

In the UK, these tests follow the ISO 10140-1:2021 series (laboratory measurement of sound insulation) and often reference ISO 717-1:2020 for the calculation of single-number ratings like Rw.

Developers, architects, and designers should only trust performance claims backed by independent, UKAS-accredited laboratories using recognised standards. Testing consistency is vital for meaningful comparisons between products.

The Testing Process: A brief overview

Third-party testing bodies such as Sound Research Laboratories (SRL) or BRE put trickle vents through rigorous compliance testing. Here’s what that involves:

1. Sample Preparation

The vent, including its frame or canopy, is installed in a standard test wall according to the manufacturer’s instructions. This setup replicates real-world conditions as closely as possible.

2. Test Chamber Setup

A two-room facility - the source and receiver chambers - is separated by a solid partition wall. The vent is mounted within this wall.

3. Noise Generation

A calibrated loudspeaker in the source room emits controlled noise across a broad frequency range (typically 100 Hz to 5000 Hz).

4. Sound Level Measurement

Microphones in both rooms measure noise levels. The difference between them, adjusted for reverberation and surface area, yields the Sound Reduction Index (Rw) or Sound Transmission Loss (STL).

5. Reporting

Results are summarised, typically including a single-number rating like Rw (weighted sound reduction index). Some reports break down performance by frequency bands, which can help target specific noise sources (like low-frequency traffic rumble or higher-frequency aircraft noise).

Acoustic ratings - what do they mean?

Vendors should share the output from third-party product testing on their website and in other collateral so customers can make informed purchase decisions. 

These results typically look something like this:

Acoustic testing reports like these show how effectively each vent and canopy combination blocks or reduces noise.

The key figure here is Dn,e,w, which indicates how many decibels (dB) of noise reduction you can expect from the product.

Note that the data also shows performance of the vents in both open and closed modes. 

Armed with this data and a sense of the decibel levels generated by certain activities, you'll see the kind of noise attenuation you will need (and should expect) from your products.

So, how loud is loud?

Here’s a quick scale to help demonstrate where everyday sounds - and a few extreme ones - really sit on the decibel chart.

A higher Dn,e,w value indicates better sound insulation. For example, a trickle vent with a Dn,e,w of 55 dB would reduce external noise by approximately 55 decibels, significantly improving indoor comfort in noisy environments.   

C; Ctr ratings adjust this number based on the type of noise you’re dealing with, such as general background sounds (pink noise) or specific noises like traffic. For instance, a C; Ctr of (-2; -3) means the vent performs slightly less effectively against those noise types compared to the overall rating. 

Testing attenuation at different frequencies

Testing should also reveal how different pitches of noise are attenuated by the vent. Look for these reports to help choose your solution based on the kind of noise disturbance you are most

Low Frequencies (125-250 Hz)

• Deep, rumbling sounds that you often feel as much as hear
• Common sources:
   
  • Heavy traffic and diesel engines
  • Underground trains and subway systems
  • Building services equipment like HVAC systems
  • Bass notes in music

Mid Frequencies (315-1000 Hz)

• The range where most everyday sounds occur
• Common sources:
  • Everyday human speech (around 500 Hz)
  • Regular traffic noise
  • Office equipment
  • General environmental sound

High Frequencies (2000-8000 Hz)

• Sharp, piercing sounds that can be particularly noticeable
• Common sources:
  • Emergency vehicle sirens
  • Aircraft noise during overhead passage
  • High-pitched machinery
  • Birds chirping

What to expect from your acoustic trickle vent based on test data

30 dB to 40 dB: Moderate Noise Reduction

• Suitable for areas with low to moderate noise levels, such as suburban neighbourhoods or quiet office environments.

40 dB to 50 dB: Good Noise Reduction

• Ideal for busier urban areas, residential buildings near highways, or schools and libraries where maintaining a quieter environment is important.

50 dB and Above: High Noise Reduction

• Best for extremely noisy environments like airports, industrial zones, or near major railway lines where significant noise attenuation is required to ensure comfort and compliance with strict noise regulations.

Conclusion

Third-party testing reports on acoustic trickle vents (such as those produced by Sound Research Laboratories for Titon) will give you an honest and exhaustive view of the noise attenuation capabilities of your chosen vent.

By comparing open/closed performance, single-number acoustic ratings (Dn,e,w), and the practical ventilation area (EA), you can ensure the final installation provides both comfort and compliance.

Read our in-depth guide to managing noise attenuation with acoustic trickle vents.