Acoustic & Sound Insulated Enclosures
Most “acoustic enclosures” on the market are a sheet metal box with a layer of foam stuck to the inside. That reduces echo inside the box. It does very little for the noise your operator hears outside it. If you have a dB target to hit — 73 dB, 70 dB, whatever your machine produces — the enclosure has to be engineered against that number, and the three things that decide whether you hit it are mass, decoupling and sealing.
Send us the machine, the noise level and the target dB
We will review the enclosure geometry, tell you what is realistically achievable at what wall thickness, and come back with a DFM proposal and indicative pricing. No obligation.
Why foam on the inside does almost nothing for the outside
This is the single most common and most expensive misunderstanding in acoustic enclosures, and it is worth being blunt about it because it determines whether your enclosure works.
Sound absorption and sound insulation are two different things.
- Absorption (rock wool, PU foam, melamine) soaks up sound already inside the enclosure. It stops the noise bouncing around the cavity and reinforcing itself. This is worth doing — but on its own it typically buys you 2–4 dB at the outside.
- Insulation (transmission loss) is what stops sound getting through the wall. That is governed almost entirely by the mass and construction of the shell itself.
If a supplier quotes you an enclosure by saying “we line it with 50 mm rock wool”, they are describing an absorption treatment and calling it an acoustic enclosure. You will measure the result and it will not meet your target.
The three things that actually decide your dB reading
1. Mass — the mass law, and why thin shell costs you twice
For a single homogeneous panel, transmission loss rises roughly 6 dB every time the panel mass doubles. In practice:
| Shell | Typical performance | Comment |
|---|---|---|
| 0.8–1.0 mm steel | Weak | Light duty only; will not reach a low dB target |
| 1.5 mm steel | Moderate | Common starting point for machine housings |
| 2.0 mm steel | Good | Typical for a 70–75 dB target |
| Double wall (mass–spring–mass) | Strong | Two skins with an elastic layer between; far better than one thick skin at the same weight |
The trade-off is weight and cost. Doubling thickness doubles steel weight and pushes up material cost and handling. This is exactly why we need your weight distribution data before quoting — it sets the base frame, the castor or foot specification, and whether the panels can be lifted by one person during service.
2. Decoupling — killing the vibration path
This is where most enclosures quietly fail after the shell is right. Sound does not only travel through air — it travels through structure. If the inner liner, the machine mounts, or the panels themselves are rigidly bolted to the outer shell, vibration goes straight through the steel and re-radiates as noise on the outside. In acoustics this is called a sound bridge or flanking path.
What we do instead:
- Machine mounted on anti-vibration mounts (rubber or spring), not hard-fixed to the base.
- Inner acoustic liner attached with resilient fixings, not screwed tight to the outer panel.
- Where panels meet, an elastic gasket rather than metal-to-metal contact.
- Pipe, cable and duct entries passed through flexible boots, because a rigid conduit into the enclosure is a direct vibration path and a direct sound leak.
3. Sealing — the failure that costs the most in the field
An enclosure can be heavy, decoupled and well lined, and still miss its target by 10 dB because of gaps. Sound behaves like water: it finds the opening.
So we treat sealing as a design line item, not a finishing detail:
- Continuous EPDM or silicone gasket on every removable panel and door.
- Doors with multi-point compression latches so the gasket compresses evenly right around, not just at the handle side.
- Sealed cable glands and brush plates for every entry.
- Acoustic louvres or baffled vents where ventilation is needed — you cannot simply cut a hole for cooling air, because an open hole is an open door for sound.
Bolted modular construction — and why we usually recommend it over welded
A welded box is stiff and cheap to make once, but it is a liability the first time the machine needs service: you cannot get a pump or a compressor out of it without cutting.
We build these enclosures bolted, as a kit of panels:
| Welded | Bolted modular | |
|---|---|---|
| Service access | Cut and re-weld | Unbolt the panel |
| Shipping | Ships assembled, bulky | Can ship flat-packed |
| On-site assembly | None | Simple, with instructions |
| Stiffness | Slightly higher | Achieved with folded returns and internal bracing |
| Sealing | Easy (continuous weld) | Requires gasket discipline — this is where care is needed |
What we build, and what we need from you
Supplied by us
- Laser-cut, folded and welded sheet metal shell — steel, stainless or aluminium, 0.5–12 mm
- Acoustic infill — rock wool, PU foam or mass-loaded barrier, cut to suit the cavity
- Anti-vibration mounts, resilient liner fixings, gaskets and compression latches
- Powder coating to your RAL, or wet paint where the specification calls for it
- Assembly, packing and export crating
What we need from you to quote properly
- The measured noise level next to the machine, and the target dB you need to reach
- Weight distribution — where the mass sits. This sets the base frame and the shell specification
- Drawings or a STEP model of the machine, or of the existing enclosure if you have one
- Any ventilation requirement, and whether the enclosure is indoor or outdoor
Have a dB target and a machine to enclose?
Send the noise reading, the target and the machine geometry. We will tell you what wall thickness and construction gets you there, and what it costs — before you commit to tooling.
Questions buyers ask us
- Can you guarantee a specific dB figure?
- We design against your target using mass, decoupling and sealing, and we can arrange third-party sound testing on a production-representative unit. What we will not do is quote a dB number without knowing the machine’s actual noise spectrum — the same enclosure performs differently against low-frequency rumble than against high-frequency whine. Give us the reading and we will tell you what is achievable.
- We already have a supplier in Europe but they are too expensive. Can you match the performance?
- This is a common reason customers come to us. In most cases the European design is a good enclosure that is priced for a different cost base. We can usually reproduce the construction — or improve the decoupling and sealing, which is where cost is often saved by less careful suppliers — at a materially lower unit cost. Send us the existing drawings or photographs and we will tell you honestly what we can and cannot match.
- Do you supply the acoustic material, or do we?
- Either. We normally source and fit the rock wool or foam ourselves so the cavity is filled correctly and the liner is fixed resiliently. If you have a specified acoustic material or a fire rating to meet, tell us and we will build to it.
- What about ventilation? The machine needs cooling air.
- This is the most common conflict in acoustic enclosures: air needs to move, sound must not. We use baffled acoustic louvres or labyrinth vents that pass air but attenuate sound. Cutting an open grille will defeat the enclosure — we will flag it in the DFM review if we see it on your drawing.
- Can the enclosure be fully stripped down?
- Yes — that is the point of the bolted construction. We design it so a panel can be removed and refitted with the gasket seating correctly afterwards, without specialist tools.
- What is the lead time?
- Prototype or first article for an enclosure of this type is typically 15–20 days after design freeze, including a round of revisions. Production batches follow at 25–35 days after prototype approval. Tooling for any dedicated pressed or cast parts is quoted and scheduled separately.
Send the drawing. We will tell you what it takes to hit your dB number.
Email the machine geometry, the noise reading and the target. You will get a DFM review, a construction proposal and indicative pricing — from the factory that will build it, not from a trading desk.
Ningbo Fulei Metal Products Co., Ltd. — sheet metal manufacturer in Ningbo, China. Laser cutting, bending, welding and assembly in-house; powder coating on audited partner lines that we specify and inspect. Exporting to the EU, US, Japan and Korea. See full capabilities.