Expert Guide
How shutters and blinds reduce noise
Louvred shutters reduce outside noise by 5 to 10 dB with louvres closed. Combined with a 32mm Duette cellular blind, the total reduction reaches 8 to 13 dB, which most people perceive as roughly half the original loudness. Solid panel shutters with a Duette behind achieve 15 to 20 dB, approaching the performance of secondary glazing. This guide covers the science, our product data, and honest recommendations by noise type.
Understanding decibels
The decibel scale is not like a ruler where each step is the same size. It is logarithmic, which means small numbers represent big changes in what you actually hear. Each 10 dB represents a tenfold increase in sound energy. So 80 dB is not a bit more than 70 dB. It contains ten times more sound energy.
What common sounds measure
| Sound | Level | What it feels like |
|---|---|---|
| Breathing | 10 dB | Almost silent |
| Quiet bedroom at night | 25 to 30 dB | Very quiet, peaceful |
| Quiet library | 35 dB | Calm, can hear a pin drop |
| Normal conversation at 1 metre | 60 dB | Comfortable |
| Busy road at 10 metres | 70 to 80 dB | Have to raise your voice |
| Motorbike passing | 85 to 90 dB | Unpleasant, difficult to talk |
| Nightclub | 100 to 110 dB | Painful over time |
What dB reductions actually sound like
| Reduction | What you hear | Everyday comparison |
|---|---|---|
| 3 dB | Just barely noticeable | Like taking one step further from the road |
| 5 dB | Clearly noticeable | Like closing a single glazed window |
| 10 dB | Sounds half as loud | Busy road becomes a quiet street |
| 15 dB | Dramatically quieter | Like closing the door to a noisy room |
| 20 dB | Sounds a quarter as loud | Busy street to quiet garden behind a solid wall |
Why small numbers matter: Even a 5 dB reduction is removing a substantial amount of noise energy, even though the number sounds modest. A 10 dB reduction halves the perceived loudness. This is often the difference between being disturbed by noise and sleeping through it.
What type of noise are you dealing with?
Not all noise is created equal. Shutters and blinds are excellent at blocking some types of noise but less effective against others. The difference comes down to frequency: low pitched sounds (bass, rumbling) are much harder to block than high pitched sounds (voices, birdsong).
Road traffic
Mixed frequency (200 to 500 Hz dominant)
Shutters provide a noticeable improvement. Traffic moves from intrusive to background. Adding a 32mm Duette behind the shutter pushes this to 8 to 13 dB, which most people describe as roughly half as loud. For severe traffic noise (motorway, A road), consider acoustic glass as the primary solution, with shutters and Duette as supplementary layers.
People talking, shouting, or arguing outside
Mid frequency (500 to 2,000 Hz)
This is where shutters really shine. A well fitted shutter makes voices outside significantly less intelligible. With a Duette behind, 10 to 15 dB reduction makes conversation outside virtually unintelligible from inside. Shouting at closing time would still be audible, but reduced from disturbing to muffled background noise. Solid panel shutters perform even better (12 to 17 dB), eliminating speech intelligibility almost entirely.
Nightclub or pub bass music
Low frequency (40 to 250 Hz)
Shutters and blinds provide minimal relief from deep bass. This is a fundamental limitation of physics, not a product shortcoming. A 50 Hz bass note has a wavelength of nearly 7 metres and passes through lightweight barriers almost unimpeded. For bass noise, the solutions are: acoustic glass with laminated PVB interlayer, secondary glazing with a 100mm or greater air gap, or planning enforcement against the noise source. Shutters will help with the higher frequency components of the music (vocals, drums, cymbals) but not the bass itself.
Aircraft overhead
Mixed frequency (100 to 2,000 Hz)
Similar to traffic. Shutters help noticeably with the mid and high frequency components. A shutter plus Duette combination (8 to 14 dB) makes aircraft noise significantly less intrusive. For homes under flight paths, laminated acoustic glass provides the most effective primary defence, with shutters and Duette adding valuable supplementary reduction.
Dogs barking, birdsong, alarms
High frequency (1,000 to 4,000 Hz)
Shutters excel here. A well fitted shutter will take the sharpness off barking dogs and make car alarms much less piercing. Combined with Duette: 12 to 18 dB reduction, which is dramatic. This is where the shutter plus blind combination genuinely approaches the performance of secondary glazing.
Neighbours through a party wall
Mixed (structure borne and airborne)
Shutters only help with the portion of neighbour noise coming through the window. If the noise is predominantly through the shared wall, shutters will make little difference. For structure borne noise (footsteps, bass), interior window treatments have zero effect. If the neighbouring property is to the side and the windows face the same direction, closing shutters on those windows will help with airborne sound travelling around the building.
Construction and roadworks
Mixed frequency (100 to 4,000 Hz)
Good for the higher frequency components (drilling, angle grinders, reversing beepers) but limited for heavy machinery thuds and ground vibration. A shutter plus Duette combination provides meaningful relief during the daytime. It will not eliminate it, but will take the worst edge off.
Our recommendations
The best combination depends on the type of noise you are dealing with and what matters most to you. Here are our recommendations based on the acoustic data.
Best combinations by noise type
| Your noise problem | Recommended solution | Expected benefit |
|---|---|---|
| General traffic noise | Any louvred shutter + 32mm RD Duette behind | 8 to 13 dB: roughly half as loud |
| Voices, pub noise, street noise | Any louvred shutter + 32mm Duette behind | 10 to 15 dB: dramatically quieter |
| Maximum noise reduction (not bass) | Solid panel shutter + 32mm RD Duette behind | 15 to 20 dB: approaching secondary glazing |
| Security + noise (ground floor) | Portchester aluminium + 32mm RD Duette | 10 to 14 dB: half as loud, with lock and key |
| Budget friendly noise reduction | Antigua 47mm + 25mm standard Duette | 7 to 11 dB: clearly noticeable improvement |
| Bass music from venue | Acoustic glass replacement + shutters | Shutters alone: minimal for bass |
| Dogs barking, alarms, sirens | Any shutter (louvres closed) | 8 to 15 dB: excellent reduction |
Six tips for maximising acoustic performance
- 1 Fit the Duette closest to the glass, with the shutter in front. This maximises the air gap between layers, which improves sound decoupling.
- 2 Choose the smallest louvre size the customer finds visually acceptable. Smaller louvres mean more material coverage per unit height.
- 3 Specify hidden tilt rod on all shutters. Centre tilt rods create small holes through the stile that let sound through.
- 4 Use Z frame where possible for a tighter fit into the window reveal, minimising gaps around the frame edge.
- 5 Close trickle vents during noise critical periods. An open trickle vent completely undermines the acoustic benefit of shutters.
- 6 Use side channels on the Duette if available. Without side channels, sound flanks around the edges of the blind.
The single biggest factor is installation quality. A well fitted shutter with tight frames and minimal gaps will outperform a premium product that has been poorly fitted. The seal around the edges matters more than the material the shutter is made from.
What to expect in practice
Interior shutters and blinds provide meaningful, noticeable noise reduction, but they are not soundproofing. Here is an honest assessment.
"Will shutters make my room silent?"
No. They will reduce noise significantly but not eliminate it. A busy road will become a quiet road, not silence.
"Will I sleep better?"
Very likely, yes. A 10 dB reduction (achievable with shutter plus Duette) halves the perceived loudness. This is often the difference between waking up and sleeping through.
"Will I still hear emergency sirens?"
Yes, absolutely. Sirens are designed to penetrate buildings. Shutters reduce them but cannot eliminate them.
"Are shutters as good as secondary glazing?"
No. Dedicated acoustic secondary glazing (20 to 35 dB) significantly outperforms shutters. However, shutters offer light control, thermal insulation, privacy, and aesthetics that secondary glazing does not.
"Do shutters help with thermal insulation too?"
Yes. The same air gap and material mass that blocks sound also provides thermal insulation. A Duette adds further thermal benefit with its trapped air pockets.
The best way to think about it: shutters and Duette together transform "I cannot relax because of the noise" into "I can hear it if I listen for it, but it does not bother me." That is a life changing improvement for many people.
Health context: The World Health Organisation links prolonged exposure to noise above 55 dB with stress, poor sleep, and cardiovascular issues. If your bedroom faces a road at 70 dB, reducing that to 56 to 60 dB with shutters and blinds brings you below this health threshold.
Technical Analysis
Acoustic fundamentals
The acoustic mass law
The most fundamental principle in sound insulation: heavier barriers block more sound.
Where TL is transmission loss in decibels, m is surface mass density in kg/m², and f is frequency in Hz. Doubling the mass adds approximately 6 dB of transmission loss. Doubling the frequency adds approximately 6 dB of transmission loss.
Key acoustic metrics
| Metric | What it measures |
|---|---|
| TL (Transmission Loss) | Sound energy reduction through a barrier at a specific frequency. Measured in dB, higher is better. |
| STC (Sound Transmission Class) | Single number rating across 125 to 4,000 Hz (ASTM E413). Higher is better. |
| Rw (Weighted Sound Reduction Index) | ISO equivalent of STC, used in UK and Europe (ISO 717-1). Measured in dB, higher is better. |
| NRC (Noise Reduction Coefficient) | Sound absorption, not blocking. Reduces echoes within a room. Scale 0 to 1.0, higher is more absorbent. |
Critical: airtightness. A 1mm gap allows approximately 6 dB of unwanted noise through. A gap area equal to just 1% of the panel area reduces transmission loss by approximately 10 dB. The smallest perimeter gap can drop isolation by 10 STC points or more.
The mass, air, mass resonance problem
Standard double glazing (4mm, 12mm gap, 4mm) is often no better than single glazing for sound. The two panes coupled by the narrow air gap create a resonance at approximately 200 to 400 Hz that negates the benefit of having two panes, precisely where traffic noise is strongest.
This is why adding an interior shutter or blind is valuable: it creates a third acoustic barrier with a different resonance frequency, breaking the coupling that limits standard double glazing.
Glass baseline performance
| Glazing configuration | Typical Rw | Notes |
|---|---|---|
| Single glazing, 4mm | 29 dB | Minimal insulation |
| Single glazing, 6mm | 32 dB | +3 dB from increased mass |
| Double glazing, 4-12-4 | 29 dB | Standard. Resonance cancels benefit. |
| Double glazing, 6-12-6 | 33 dB | Heavier glass helps more than wider gap |
| DG, 6-12-6.4L (1 laminated) | 37 dB | One laminated pane. Significant. |
| Triple glazing, 4-12-4-12-4 | 33 dB | Two resonances can be problematic |
| Acoustic, 6.4L-16-6.4L | 40 to 43 dB | Two laminated panes. Best standard. |
| Acoustic, 6.8L-20-8.8L | 45 to 48 dB | Specialist acoustic glazing |
Laminated glass with PVB interlayer provides the biggest single acoustic improvement. Gas fill (argon, krypton) has negligible acoustic effect. Asymmetric pane thicknesses help because they have different coincidence frequencies.
Shutter material properties
| Range | Material | Surface mass (kg/m²) | Louvre sizes |
|---|---|---|---|
| Antigua | 100% MDF | 7.0 to 8.5 | 47, 63, 76, 89mm |
| Cuba | MDF frame + Ayous/Basswood | 7.3 to 7.9 | 47, 63, 76, 89mm |
| Fiji | 100% solid hardwood | 7.5 to 9.0 | 63, 76, 89mm |
| Hawaii | Poplar + Paulownia louvres | 6.0 to 7.5 | 63, 76, 89mm |
| Hampton | HSPVC (fauxwood) | 7.5 to 9.0 | 63, 76, 89mm |
| Java | 100% waterproof PVC | 8.0 to 12.0 | Limited |
| Portchester | Architectural aluminium | 10 to 13 | 89mm only |
| Solid panel | Various | 10 to 18 | N/A |
Theoretical transmission loss by material
| Range | kg/m² | 250 Hz | 500 Hz | 1 kHz | 2 kHz | 4 kHz |
|---|---|---|---|---|---|---|
| Hawaii (lightest) | 6.5 | 17 dB | 23 dB | 29 dB | 35 dB | 41 dB |
| Cuba | 7.6 | 19 dB | 25 dB | 31 dB | 37 dB | 43 dB |
| Antigua (MDF) | 7.8 | 19 dB | 25 dB | 31 dB | 37 dB | 43 dB |
| Java (PVC) | 10.0 | 21 dB | 27 dB | 33 dB | 39 dB | 45 dB |
| Portchester (aluminium) | 11.5 | 22 dB | 28 dB | 34 dB | 40 dB | 46 dB |
| Solid MDF panel (25mm) | 17.5 | 26 dB | 32 dB | 38 dB | 44 dB | 50 dB |
Theoretical maximums for perfectly sealed solid panels. Real louvred performance is 15 to 20 dB lower due to gap leakage.
Real world shutter performance
| Range | Louvres closed | Open 45° | Solid panel equivalent |
|---|---|---|---|
| Antigua (MDF, 47 to 89mm) | 6 to 9 dB | 2 to 4 dB | 12 to 15 dB |
| Cuba (MDF + timber, 47 to 89mm) | 6 to 9 dB | 2 to 4 dB | 12 to 15 dB |
| Fiji (solid timber, 63 to 89mm) | 6 to 9 dB | 2 to 4 dB | 12 to 15 dB |
| Hawaii (Poplar + Paulownia) | 5 to 8 dB | 2 to 3 dB | 10 to 13 dB |
| Java (PVC) | 7 to 10 dB | 3 to 5 dB | 13 to 16 dB |
| Hampton (HSPVC) | 6 to 9 dB | 2 to 4 dB | 12 to 15 dB |
| Portchester (aluminium) | 7 to 10 dB | 3 to 5 dB | 14 to 17 dB |
| Solid panel shutter | N/A | 12 to 17 dB | |
All louvred shutters cluster in the 5 to 10 dB range because louvre gap leakage is the dominant factor, not material density. The heavier materials (Portchester, Java) have a modest 1 to 2 dB advantage. Solid panels are the clear acoustic winner.
Air gap between glass and shutter
| Air gap | Benefit | Notes |
|---|---|---|
| 0 to 20mm | Minimal | Too close, coupled vibration |
| 20 to 50mm | +2 to 4 dB | Starting to decouple |
| 50 to 100mm | +4 to 8 dB | Effective decoupling |
| 100 to 200mm | +8 to 12 dB | Optimal range |
Cellular blinds (Duette) acoustics
25mm vs 32mm cell size
The 32mm cell traps approximately 65% more air per cell than the 25mm, providing better low frequency absorption. The estimated difference is 0.5 to 1.5 dB in favour of the larger cell.
Room darkening aluminium backing
Room darkening versions are acoustically equal to or marginally better than standard Duette. The aluminium foil adds mass, reduces fabric porosity, acts as a reflective barrier, and functions as a constrained layer damper. The aluminium is an acoustic asset.
Performance data
| Configuration | dB reduction (additional to glass) |
|---|---|
| 25mm standard Duette | 2 to 3 dB |
| 32mm standard Duette | 2.5 to 4 dB |
| 32mm RD Duette | 3 to 4.5 dB |
| Architella (double cell) | 3 to 5 dB |
| Architella RD | 3.5 to 5.5 dB |
NRC: 0.35 to 0.55 (single cell), up to 0.70 (Architella). RD versions: NRC up to 0.60, peaking at 0.89 to 1.02 at 4,000 Hz. With side channels: 4 to 6 dB independently measurable. STC improvement: +4 to +8 points.
Combined systems: shutters and cellular blinds
System configuration: Glass | Air Gap 1 | Duette | Air Gap 2 | Shutter
| Configuration | Total additional dB |
|---|---|
| Louvred shutter + 25mm Duette | 7 to 11 dB |
| Louvred shutter + 32mm Duette | 8 to 12 dB |
| Louvred shutter + 32mm RD Duette | 8 to 13 dB |
| Louvred shutter + Architella RD | 9 to 14 dB |
| Solid panel + 32mm Duette | 14 to 19 dB |
| Solid panel + 32mm RD Duette | 15 to 20 dB |
Frequency analysis
| Frequency band | Shutter | Duette | Combined |
|---|---|---|---|
| 63 to 125 Hz (deep bass) | 1 to 3 dB | 0 to 1 dB | 1 to 4 dB |
| 125 to 250 Hz (bass) | 3 to 6 dB | 1 to 2 dB | 4 to 7 dB |
| 250 to 500 Hz (low mid) | 5 to 8 dB | 2 to 3 dB | 6 to 10 dB |
| 500 to 1,000 Hz (mid) | 7 to 10 dB | 3 to 4 dB | 9 to 13 dB |
| 1,000 to 2,000 Hz (upper mid) | 8 to 12 dB | 3 to 5 dB | 10 to 15 dB |
| 2,000 to 4,000 Hz (high) | 10 to 15 dB | 4 to 6 dB | 12 to 18 dB |
Complete acoustic performance matrix
| Glazing | Glass alone | + Shutter | + 25mm Duette | + 32mm RD Duette |
|---|---|---|---|---|
| Single 4mm | 29 dB | 34 to 39 dB | 36 to 41 dB | 37 to 42 dB |
| DG 4-12-4 | 29 dB | 34 to 39 dB | 36 to 41 dB | 37 to 42 dB |
| DG 6-12-6 | 33 dB | 38 to 43 dB | 40 to 45 dB | 41 to 46 dB |
| DG 6-12-6.4L | 37 dB | 42 to 47 dB | 44 to 49 dB | 45 to 50 dB |
| Acoustic 6.4L-16-6.4L | 42 dB | 47 to 52 dB | 49 to 54 dB | 50 to 55 dB |
Installation quality and flanking transmission
Even the best acoustic materials are undermined by poor installation. These are the most common paths where sound bypasses the shutter.
| Flanking path | Impact | Mitigation |
|---|---|---|
| Frame to reveal gap | 3 to 5 dB loss | Foam seal, tight frame fit |
| Louvre to stile gaps | 2 to 4 dB loss | Precision manufacturing |
| Panel meeting stiles | 2 to 3 dB loss | Good hinges, magnetic catches |
| Tilt rod holes | 1 to 2 dB loss | Hidden tilt rod |
| Ventilation openings | Catastrophic | Close trickle vents |
| Structure borne vibration | Zero mitigation | Beyond window treatment scope |
Shutter ranges ranked by acoustic performance
| Rank | Range | dB reduction | Key factor |
|---|---|---|---|
| 1 | Solid panel | 12 to 17 dB | No louvre gaps. Maximum mass law benefit. |
| 2 | Portchester | 7 to 10 dB | Highest surface mass (10 to 13 kg/m²). Lock pulls tight. |
| 3 | Java | 7 to 10 dB | High PVC density. May seal slightly better. |
| 4= | Cuba / Antigua / Hampton | 6 to 9 dB | Mid range density. Cuba/Antigua have 47mm option. |
| 7 | Fiji | 6 to 9 dB | Premium timber. Natural variation in fit. |
| 8 | Hawaii | 5 to 8 dB | Lightest louvres but engineered consistency. |
Methodology and confidence
Glass STC/Rw ratings are derived from published standards (high confidence). Material densities come from manufacturer specifications (high confidence). Mass law calculations use fundamental physics (high confidence). Shutter dB reductions for louvred products are extrapolated from published studies on similar barriers (medium confidence). Combined system performance is modelled from the individual component data with limited real world validation (medium confidence).
Important note: No ISO 140-3 or ASTM E90 laboratory test data exists for interior shutters from any manufacturer worldwide. No published Rw or STC rating exists for any interior louvred shutter product. The figures in this guide represent our best assessment based on available science and nearly four decades of installation experience. We believe in transparency about what we know and what we are estimating.
Frequently asked questions
Do shutters reduce noise?
How many decibels do shutters reduce?
Are shutters as good as secondary glazing for noise?
Which shutters are best for noise reduction?
Do shutters block traffic noise?
Do shutters stop bass noise from pubs and nightclubs?
What is better for noise: shutters or curtains?
Do Duette blinds reduce noise?
Will shutters help me sleep better?
Does the air gap between glass and shutter matter for noise?
Last reviewed: by David D'Ambrosio, Technical Director, BBSA Immediate Past President
Concerned about noise in your home?
We can advise on the best combination of shutters and blinds for your specific noise situation. Request a brochure or arrange a consultation.