Treat a noisy production hall as a machine problem and you end up fighting a background level that no single enclosure will remove. In a hard, reflective room the sound of every source adds up and comes back from all directions. This article explains what reverberation time tells you about a large room, where it stops being enough, what the targets are, and in which order absorption pays off.

Large halls turn reflective almost by default

Steel structure, concrete floor, trapezoidal sheet roof and ten metres of headroom create an environment in which sound loses very little energy. Every component is reflected many times over before it fades. What remains settles across the whole floor as a diffuse field, which in acoustic terms shows up as a long reverb time.

The level at a given workstation comes only partly from the nearest machine. The larger share returns from the room itself, fed by equipment standing twenty or thirty metres away. Capping the loudest machine therefore changes surprisingly little.

Where exactly does the line between the two disciplines run? A look at building acoustics vs. room acoustics sorts that out quickly. One protects against sound travelling between rooms, the other organises sound inside a single room.

Hard surfaces and large volumes as the root cause

Concrete, screed, steel and glass reflect almost completely. Add a volume of several thousand cubic metres and sound has long paths and many chances to return. Without absorbing surfaces there is simply nothing in the room that converts acoustic energy into heat.

Nobody expects a sound proof hall in manufacturing, and that is not the goal. Hall extensions regularly make things worse, because a new bay adds volume while rarely adding absorption.

How to spot the problem on the shop floor

Watch for two signals. The first is communication. People raise their voices instead of speaking, announcements arrive unintelligible, warning signals disappear into the background.

The second signal is the lack of a difference between locations. If it is barely quieter thirty metres from the press than right beside it, the press is not the issue. The room is.

What reverberation time tells you and where it stops

Reverberation time describes how long the level takes to fall by 60 dB after a source is switched off. For classrooms, offices or concert halls it is a sensible and well established value, and the shorthand reverb time means exactly the same thing.

In a workshop hall of several thousand cubic metres, with unevenly distributed fixtures and sources that run continuously, it falls short. There is no evenly diffuse sound field in such a room, but a level distribution that varies noticeably from place to place.

That is why industrial acoustics works with a second value that captures precisely this spatial distribution.

What the value measures and what it leaves open

Reverberation time gives you an average across the room. How quickly the level drops as you move away from a source is something it does not tell you. Two halls with an identical reverberation time can therefore feel very different.

For workstations that distance is exactly what matters. If noise from the neighbouring bay is broken down on its way to the workbench, the person working there benefits directly.

Level drop per doubling of distance

This value states how many decibels the level falls when the distance to the source doubles. It is measured between 0.75 and 6 metres in the octave bands from 500 to 4,000 hertz.

Outdoors it would be around 6 dB. An acoustically poor hall reaches 1 to 2 dB, a well equipped one 4 dB and above. That turns the success of a measure into something you can demonstrate rather than claim.

Target values for industrial workrooms

Two routes lead to the state of the art, and only one of them has to be met. Either the mean sound absorption coefficient across the octave bands from 500 to 4,000 hertz reaches at least 0.3, or the level drop per doubling of distance reaches at least 4 dB.

The wrong standard gets applied here regularly. DIN 18041 governs acoustic quality in occupied rooms such as schools, nurseries and offices, and that is also where an optimum reverberation time in the classic sense belongs. For workrooms and production halls, DIN EN ISO 11690 is the relevant standard, supported by the IFA noise control data sheet LSA 01-234.

Two routes to the same goal

The absorption coefficient describes how the room is equipped, the level drop describes how it actually behaves. The first is easier to determine during planning, the second is more convincing at handover.

We recommend tracking both. The coefficient drives material selection, the level drop proves the effect at the end.

Which rules apply to which type of room

Applying classroom targets to production floors costs time and money in practice. Keep that allocation clean from the start.

Wherever people speak and take calls, in a hall office for instance, different benchmarks apply than on the production floor right next to it.

Put absorption where it does the most

The hall ceiling is the largest continuous reflecting surface and therefore the first place to look, because no other surface moves the rt60 reverberation figure as much. In many halls it is enough on its own. Further measures then become unnecessary.

Where services, ventilation or crane runways occupy the ceiling, vertically suspended acoustic baffles do the same job on a smaller footprint. They work on both faces and fit between existing equipment.

Sorted sensibly, the order looks like this:

• Ceiling absorption across the whole production area as the baseline measure
• Acoustic baffles wherever the ceiling is already occupied by services
• Wall absorbers in the upper wall zone opposite loud equipment
• Acoustic screens directly between a source and the neighbouring workstation
• Enclosures for individual machines that stand out clearly

Ceiling absorbers and baffles first

Both types attack the diffuse field, meaning the share that creates the background level and stretches the reverberation time. Because production halls are dusty, draughty and damp, suitable industrial sound absorbers are built accordingly robust.

What counts is area, not material thickness alone. Half a ceiling in premium material achieves less than a full ceiling in a solid standard build. That order surprises many people.

Wall absorbers and screens close to the machines

Wall surfaces work mainly when they sit in the upper zone and face the source. Lower down, racking, benches and material trolleys block the surface anyway.

Acoustic screens catch the reflection before it spreads through the room. They do not replace ceiling absorption, but they noticeably reinforce it.

What carpet, curtains and acoustic panels cannot do

These solutions absorb almost exclusively high frequencies. The industrial background level sits well below that, in the range of 250 to 500 hertz and partly lower still.

Decorative acoustic elements from the office world therefore change little in a production hall. Measured against the area actually required, they are far too small anyway.

Calculate first, install second

Work on this kind of project starts at the computer, not in the warehouse, because absorber area cannot be estimated sensibly. A model to VDI 3760 simulates sound propagation in the room in advance, compares options and determines the area needed before any material is ordered. In practice that means you calculate reverberation time and level drop for each variant rather than guessing at them.

In an existing building, measuring the sound propagation curve to DIN EN ISO 14257 provides the baseline. Success can later be proven against it, which is regularly required for investments of this size.

Model the propagation instead of estimating area

Will partial ceiling coverage do, or are wall surfaces needed as well? The calculation answers that early, and incidentally shows what a planned hall extension will cost acoustically.

A material order turns into a planning decision with a defensible basis.

Digital measurement as the planning basis

We survey the hall with a high-resolution 3D scanner and carry the digital model into 3D CAD design. Absorber surfaces, crane runways, sprinklers and service routing then line up to the millimetre before the first element is manufactured.

In halls that have grown over decades, this step removes the usual surprises during installation.

Production halls and workshops need different answers

Two types of task come up in practice. In a large production hall the background level from many distributed sources dominates and lifts the reverberation time across the entire floor, which makes area on the ceiling and upper walls the deciding factor.

The second case follows a different logic. Few but very loud sources can be assigned individually. Here a combination of absorption and screening achieves more than area alone.

For comparison, it helps to look at the typical requirements for workshop soundproofing, where manual workstations and machines sit close together.

Large production halls with many distributed sources

The more evenly the sources are distributed, the more evenly the absorption has to be. Isolated measures at individual machines then vanish in the overall level, however good they are in themselves.

Ceiling area pays off most clearly here, because it reaches every workstation equally.

Small workshops, hall offices and control rooms

Where people speak, take calls and document, absorption alone is not enough. A room-in-room system separates the use acoustically and creates a zone in which concentration remains possible.

Control rooms and supervisor offices benefit twice, because they keep visual contact with production at the same time.

What acoustic treatment actually delivers

The question of measurable benefit comes up early in every project. Bringing down the reverb time is the mechanism, but the figure that convinces a management team is the level in dB(A). With machine noise, reductions of roughly 1 to 6 dB(A) are typical, and at greater distance from the sources 10 dB(A) and more. Where speech noise dominates, results land at around 8 dB(A).

The outcome depends on the starting point. A ceiling that is already partly covered delivers less than a bare hall. A single dominant source right at someone’s ear needs an enclosure on top.

What changes in daily operation:

• Communication without shouting, even across several metres
• Warning signals and announcements are reliably heard again
• Fatigue across the shift drops noticeably
• Assessment level falls and creates room in the risk assessment

Realistic level reduction by starting condition

The greatest leverage sits in a completely untreated hall with a sheet metal roof. Where partial surfaces already absorb, the gain is smaller. That should be clear before the investment.

We therefore calculate what is achievable beforehand, rather than promising a blanket decibel figure. Reliability beats a quick effect here.

Effects beyond the level

Less reverberation means better speech intelligibility, and that feeds directly into coordination, instruction and error rates. New staff find their feet faster when instructions arrive without repetition.

The way the site is perceived as an employer changes too, which is no side issue when skilled people are scarce.

From analysis to installation from a single source

We measure the reverberation time and the propagation curve on site, calculate the options, design, manufacture in our own plant with elements up to 6 metres long, and install with our own fitters. Production stops only for as long as it genuinely has to.

This matters particularly in acoustics, because absorber surfaces collide with hall services, fire protection and crane runways as soon as planning and manufacturing run separately. How acoustic and structural measures complement each other is covered in the overview of soundproofing for industrial halls.

Our recommendation for getting started is deliberately lean. Have the sound propagation curve of your hall measured first, because that single value decides whether a ceiling measure will do or whether more is needed. Talk to us and we will look at your hall and calculate the options.

Frequently asked questions

Which value governs acoustics in an industrial hall?

The level drop per doubling of distance, measured between 0.75 and 6 metres, is the governing value, not the reverberation time on its own. At least 4 dB counts as the state of the art. Alternatively a mean sound absorption coefficient of at least 0.3 across the octave bands from 500 to 4,000 hertz is sufficient.

How do you measure reverberation time in a production hall?

To measure reverberation time in practice, the established method is the interrupted noise or impulse response procedure to ISO 3382-2, evaluated as RT60. In an industrial hall the result should always be read together with the sound propagation curve, because a single average hides the spatial differences that matter at a workstation. An rt60 reverberation figure on its own does not tell you how far the noise of one machine travels.

Does DIN 18041 apply to production halls?

No. DIN 18041 covers acoustic quality in occupied rooms such as schools, nurseries and offices. For workrooms and production halls, DIN EN ISO 11690 is the relevant standard, supported by the IFA noise control data sheet LSA 01-234.

Is ceiling absorption alone enough?

In many halls yes, because the ceiling provides the largest free reflecting surface. With very high rooms, heavily built-up ceilings or individual dominant machines, wall absorbers, screens or an enclosure are added. The calculation shows in advance which case applies.