Ventilation Silencer

Existing Challenges

Urban traffic noise – As cities expand, more homes, hotels, and offices are located next to major roads. Excessive noise levels harm both physical and mental health.
The open‑window dilemma – Even with high‑performance soundproof windows, opening them lets in noise, dust, and pollution.
Wall‑mounted or window‑mounted ventilators – Drilling through walls or glass introduces fresh air, but these units lack proper silencing ducts. Noise travels straight through the ventilation path.
Air‑conditioning with fresh‑air function – As of May 2026, many new AC units (≥1 hp) offer 30–60 m³/h of fresh air, priced at 2,700–4,000 CNY. For households with existing AC, upgrading means replacing the whole unit.
Limited market options – Only two companies (a listed environmental firm and Soundscape Technology) produce ventilation silencers in China as of May 2026. The former’s product is structurally complex and expensive, and they do not offer residential installation services.
Niche market, little R&D – Very few companies invest in this field, leaving a long‑unmet demand.

Functional Advantages

Eco‑friendly sound‑absorbing materials – We use polyester fibre or silk‑like acoustic foam, which have higher sound absorption coefficients than the polyurethane foam used by competitors.
Dual ball‑bearing axial fan – 24 V DC, infinitely variable speed, max 12,000 rpm, static pressure 495 Pa, airflow 155 m³/h, power 19.2 W.

The axial fan produces predominantly broadband turbulent noise with energy concentrated in the mid‑high frequency range (500–4,000 Hz) – a “pink‑noise” spectrum that is more comfortable to the ear and highly absorbable by our silencing duct.
In contrast, centrifugal fans (used by others) generate discrete‑tone noise with prominent low‑frequency components (63–500 Hz) – the annoying “hum” that is difficult to attenuate.

Longer silencing duct, thicker absorption layer – Our integrated duct exceeds 1 metre in length. It uses a micro‑perforated round tube (Ø70 mm) wrapped in 30 mm of silk‑like acoustic foam. This structure delivers resonant absorption for low frequencies and reflective absorption for high frequencies.
Easy filter replacement – Simply pop off the silicone cover on the silencer surface to access and replace/clean the air filters at both ends. Competitors require removing the entire aluminium panel, which is far less user‑friendly.
Universal compatibility & long‑term serviceability – We custom‑mould only the outer shell and airflow guides – these are as durable as aluminium extrusions and will never need replacement. All consumable parts (fan, silencing duct, filter media) are standard off‑the‑shelf items available on e‑commerce platforms.
Why choose us? – Our ventilation silencer does not compromise sound insulation. You get both fresh air and quiet.

R&D History

2009 – Founder graduated in Mechanical Design & Manufacturing.
2010 – Joined the R&D department of a Shenzhen acoustics company, tasked with developing ventilation‑soundproof windows.
2010 (cont.) – At that time, no domestic products or references existed. Using Google (still accessible then), we extensively researched international solutions for roadside residential noise.
2011 – After compiling data, we realised that in Japan, Germany, the UK, and the US, ventilation‑soundproofing is integrated into building design – they do not rely on window retrofits.
2011 – Developed a dual‑window ventilation‑soundproof system for Shenzhen’s arterial roads. However, high cost, difficult dust cleaning, and poor usability led to market rejection. The company abandoned the project; the founder left to pursue it independently.
2016 – Shenzhen Soundscape Technology developed the first stand‑alone ventilation silencer (independent of windows). Still, costs remained too high for most households.
2020 – Granted utility model patent:
“A New‑Profile Ventilation Silencer for Soundproof Doors and Windows”
Inventors: Yang Qinyu, Zhou Zhiliang, Zhuang Hongyan
Patent No.: ZL 202020780551.5 (filed 12 May 2020)
Assignee: Shenzhen Soundscape Technology
Verification: CNIPA
2025 – After 15 years of continuous R&D, we finalised the current design. It delivers higher airflow, better noise reduction, and significantly lower manufacturing costs by using standard materials – making it accessible to every home.

Simplified Theoretical Analysis

Formula:
ΔL = φ(α₀) × (P/S) × L

ΔL = insertion loss (dB)
φ(α₀) = attenuation coefficient (depends on material absorption)
P = perimeter of the duct cross‑section (m)
S = cross‑sectional area (m²)
L = effective silencing length (m)

Our ultra‑fine silk‑like acoustic foam gives φ(α₀) = 0.93 and P/S = 23.
Theoretical insertion loss at L = 1 m → 20.7 dB(A).
In practice, airflow regeneration noise increases with velocity. At 2–3 m/s, the actual insertion loss is approximately 15–18 dB(A) per metre.
Optimal duct length: between 1.5 m and 2.5 m.

Shorter than 1.5 m gives insufficient attenuation.
Longer than 2.5 m causes excessive airflow resistance and reduced volume.

Important: Regularly check and replace the air filter – a clogged filter reduces airflow and increases wind noise.

Laboratory Test Results

Test setup:

Steady‑state white noise at 90 dB(A).
Silencer installed in the reserved space of our G35/G40/G60 soundproof windows (window size: 1500 mm × 1500 mm, frame sealed with cement mortar).
Effective silencing duct length = 1000 mm, airflow velocity = 2 m/s.

Measured insertion loss: approximately 18 dB(A).

The outlet diameter is only 110 mm – the small sound‑transmitting area further dilutes residual noise once it diffuses into the room, making it practically negligible to the window’s overall acoustic performance.

User Instructions

Stand‑alone design – can be flexibly paired with different soundproof windows.
Outlet diameter: 110 mm. At 2 m/s, airflow is 34 m³/h – meeting the minimum fresh‑air requirement of 30 m³/h per person (GB/T18883‑2022) to avoid stuffiness.
Power supply: 9–24 V DC variable transformer, driving the axial fan. Airflow up to 60 m³/h – minimal noise while ensuring indoor freshness.
Dual air filters (inlet and outlet) with activated‑carbon dust cartridges – washable and reusable. Replace or clean every 180 days for roadside homes (silicone cover access).
Optional PM2.5 filter (HEPA H12) – reduces airflow by 40–60% and increases wind noise significantly.
All consumables (filters, fan, silencing tube) are standard parts available online – no specialist required; simply unscrew and replace.

Summary

For residents near busy roads, our ventilation silencer solves the age‑old conflict: open windows = noise and dust; closed windows = stale air. It keeps noise out while delivering filtered fresh air. Whether renovating, replacing all windows, or retrofitting, this is the ideal choice for a healthier, quieter home.

Frequently Asked Questions

Q1: Isn’t this against physics? How can you have ventilation without letting sound in?
A: It is a well‑established acoustic principle. While soundproof windows are common, silencers are less familiar. Our device is a fan‑equipped silencer installed on the window – it brings in fresh air while blocking noise.

Q2: Does it work for sudden high‑pitched sounds like car honks?
A: Yes – it is highly effective for high frequencies. But for roadside homes, low‑frequency noise is the real challenge. Our micro‑perforated tube (Ø70 mm, plate thickness ≤0.6 mm, hole diameter ≤0.3 mm, open area ≥20%, 30 mm backing cavity) provides strong resonant absorption at low frequencies. The 30 mm silk‑like foam wrap absorbs random‑incidence high‑frequency waves. In practice, we balance duct diameter (for airflow) and foam thickness (for size). By increasing silencer length, we achieve higher overall performance.

Q3: How much sound insulation is lost when ventilating?
A: The silencer housing is made of 2.0 mm stainless steel, with only a 92 mm inlet that leads to a curved transition and a >1 m silencing duct. With the fan off, no leakage or sound transmission is detectable – the silencer does not degrade the window’s insulation. When fan is running at ≤2 m/s, airflow regeneration noise is a faint “pink noise” around 35 dB(A) (500–2,000 Hz) – barely noticeable. At 5 m/s, it becomes a stronger breeze with louder noise (~45 dB(A), 800–4,000 Hz), which may be uncomfortable for sensitive users. We recommend keeping velocity below 2 m/s.

Q4: Can the filter handle exhaust fumes and PM2.5? Is it expensive?
A: We use a 100×100×20 mm filter slot. HEPA H12 filters that capture PM2.5 and exhaust particles are available online for 20–30 CNY each (as of May 2026). Our axial fan has low static pressure – using HEPA reduces airflow by 40–60%. Our standard filter is a carbon‑impregnated foam (good for general dust and odours). For users who accept lower airflow, they can upgrade to HEPA themselves.

Q5: I’ve already moved in – can this be installed without making a mess?
A: Absolutely. We simply replace a glass panel with the silencer unit – it is completely independent of the window structure. No major disruption.

Q6: Will it work with sliding or inward‑opening windows?
A: As long as soundproof windows can be fitted, our silencer can be adapted.

Q7: Won’t it let in cold air in winter when left on overnight?
A: The airflow is modest (20–60 m³/h) – most users feel little temperature change.

Q8: What about insects and dust – can they get through? How do you clean the duct?
A: The intake has a filter that blocks insects and large particles. Simply replace or clean the filter – the duct itself stays clean.

Q9: Does it affect privacy? Can outside hear us or see inside?
A: The silencer blocks sound in both directions – outside cannot hear indoor conversations. The stainless‑steel housing and staggered inlet/outlet design make it impossible to see through.

Q10: What is the price? Why is it more expensive than ordinary soundproof windows?
A: As of May 2026, the unit price is 1,500 CNY for the base length (1.5 m). For longer lengths, add 1,000 CNY per metre. Typical lengths are 1.5–2.0 m, so the total is around 1,500–2,000 CNY.

Q11: Do I need one for every room?
A: No – only in rooms where you need both quiet and fresh air. Most customers install it only in the bedroom.

Q12: Is this a real necessity or a gimmick? How do I know it works?
A: If you live on a busy road, dust is as bad as noise. Even with high‑performance windows, opening them brings in both. After using our silencer, you can keep windows closed and still enjoy filtered fresh air. Over the years, we’ve followed up with about 100 users – they consistently report less dust, better sleep, and a feeling of living away from the traffic. This is a proven, practical solution.

Q13: Why not just install a whole‑house ventilation system?
A: If you have a central fresh‑air system with silencing ducts, that works fine – you wouldn’t need our silencer. But for existing homes that cannot retrofit ductwork, our window‑mounted solution is the best alternative. Wall‑mounted or glass‑mounted ventilators without silencing ducts simply let noise in – they ventilate but do not quiet.

Q14: I see cheaper “ventilation soundproof” stickers online – how are they different?
A: Those are basic window ventilators – they have a simple fan and filter but no silencing duct – they offer no noise reduction. Such products were tried in Shenzhen around 2012 but proved useless; residents ended up sealing them. Since 2018, developers no longer install them.

Q16: What is the warranty? What if it breaks – will it affect the window?
A: The soundproof window itself has a 5‑year warranty. The silencer is an independent unit – the only electronic part is the fan. Even if the fan fails, the silencer still blocks noise (and the window works fine). The fan carries a 2‑year warranty. After that, you can buy an identical fan online (standard model) and replace it with a few screws – it’s that simple.