Noisy Restaurant: Ceiling, Walls, Then Curtains

By Tim Chaikhraziev, RF Specialist | Telos Machina inc.

It's 7 p.m. and the room is filling up. Voices rise, guests lean across the table, staff ask customers to repeat their orders. Empty, the same room seemed quiet enough. Same tables, same chairs, same walls. The difference is entirely in what's happening inside them right now.

Nothing is wrong with your guests. What makes a restaurant noisy is hard surfaces that keep sound alive, plus the Lombard effect, which pushes everyone to talk over everyone else.

This article is for owners and managers of cafés, bistros and restaurants in Sherbrooke, Magog or elsewhere in the Eastern Townships, whose dining room leans on hard finishes and big windows.

You'll learn to gauge your own room, then the honest order of fixes: the ceiling first, the walls second, and only then curtains on the glass. Yes, even on a curtain maker's blog.

A fix chosen without knowing what a hard room does to sound is a gamble.

Why Your Dining Room Gets Loud at 7 p.m.

Your dining room gets loud because of reverberation, which makes sound linger, and the Lombard effect, which makes voices rise. Each one feeds the other.

Reverberation: Sound That Won't Die Down

Reverberation is sound that keeps bouncing after the voice has stopped. It's measured with RT60: the time sound takes to die away.

Think of a billiard ball: it loses a little energy off each cushion and keeps rolling a long while. Sound behaves the same way.

An untreated restaurant with hard finishes (exposed brick, concrete, glass) typically measures an RT60 of 2.0 to 2.5 s. Design guides, from the WELL Building Standard to the UK's BS 8233, instead target 0.6 to 1.0 s for a dining room, and a casual restaurant can tolerate 0.8 to 1.0 s.

Here's how I put it:

You could place the best sound system in the world in a bathroom and it will still sound horrible.

The room decides, not the equipment. No amount of better speakers, sharper menus, or friendlier service changes what a hard, reflective room does to sound.

The Lombard Effect: Noise Feeds Itself

The Lombard effect is the involuntary rise in vocal effort under noise. When the volume around you climbs, your voice follows, without you deciding it. French ear-nose-throat physician Étienne Lombard first described it in 1911.

In 2022, a study published in Scientific Reports put the tipping point at about 57 dB(A): past that level, vocal effort climbs faster.

Then the loop sets in. One table talks louder, the next table raises its voice to be heard, and the noise feeds itself. Above an RT60 of about 1.2 s, sound levels climb from roughly 65 to 80 dB(A) and beyond.

In the field, the Journal of the Acoustical Society of America published measurements taken in ten occupied food-service establishments: 45 to 82 dB(A).

That 1.2 s threshold falls between a bare room and the guides' target. Lowering reverberation is what breaks the loop.

Measuring the Noise Before You Spend

You can gauge your own room yourself, at no cost and before any call. None of the four checks below needs special equipment beyond what's already in your pocket.

1. A sound-meter app on your phone. Take a reading at the peak of service, then another in the empty room, knowing that an app gives you a ballpark figure, not a measurement. AcousPlan's restaurant acoustic design guide targets 70 to 75 dB(A) at peak service for a casual restaurant and recommends keeping a full restaurant's noise under roughly 78 dB(A), the threshold where the loop takes over. The Lombard effect starts lower, but this target accepts a lively room and only rules out the runaway.
2. The hand-clap test. In the empty room, clap your hands once, sharply. A fast, metallic repeat that rings out is a flutter echo bouncing between two hard parallel surfaces, while a long tail that simply fades is reverberation.
3. Count the hard surfaces. Walk the room. Ceiling, floor, walls, tables, the front of the bar. Note especially exposed brick, concrete and glass, the hard finishes of an untreated room.
4. The windows. If your room faces a commercial street, check whether the storefront window is the largest hard surface on your walls. It's also the one where panels are hardest to place.

The Options Compared, from Ceiling to Curtain

Noise solutions don't treat the same problem, and they don't go in the same place.

What Each Solution Treats

Panels, foam, soft furnishings and curtains absorb sound inside the room, while SONOpan works inside the wall. Before choosing, compare where each one goes, how easily it comes down, how it looks and how it's maintained.

Solution	What it treats	Where it goes	Reversible?	Look	Upkeep
Ceiling panels or baffles	The reverberation of the whole room, above every table	Mounted on or hung from the ceiling	Yes, but anchored into the structure	Visible, various finishes	Dusting
Wall acoustic panels	Reverberation and reflections at head height	On the walls	Yes, but screwed on: holes to patch	Visible, various finishes	Dusting
Acoustic foam	Mid and high frequencies, almost nothing below 250 to 300 Hz	Walls or ceiling	Limited: often glued	Studio look	Dusting
SONOpan inside the wall	Sound passing through the wall or ceiling, not the room's echo	Inside the wall or ceiling cavity, behind the drywall	No, it's construction	Invisible	None
Soft furnishings (upholstered banquettes, cushions)	A little absorption where people sit	Seating areas	Yes	Warm	Fabric cleaning
Curtains on the glass	Reflections off the glass and part of the room's reverberation, in the mid and high frequencies	In front of windows and glazed walls	Yes, no construction: they come down	Soft, wide fabric choice	Dry cleaning, about once a year in food service

The Order: Ceiling, Walls, Then Curtains

My order doesn't change: the ceiling first, the walls second, curtains on the glass third.

The ceiling, because it's the one large hard surface above every table, uninterrupted by a window or a door. Walls come next, because they bounce sound back at head height, right where people talk. That doesn't mean covering everything. An over-treated room sounds dead.

As for SONOpan, often mentioned whenever restaurant acoustics comes up, it goes inside the wall and carries a standalone STC of 27 on its own, the rating for sound passing through a partition. That rating feeds into the full wall assembly's score, together with the drywall and the insulation, but the panel does nothing for your dining room's echo.

That leaves the glass, which acoustic panels can't cover without blocking the view. A curtain adds soft surface there with no construction, and it comes down.

Third doesn't mean minor: it's simply where a curtain fits in a dining room.

What a Curtain Does in a Restaurant Dining Room

In a restaurant, a curtain absorbs the sound bouncing off the glass and the walls near the tables, especially when it's heavy and gathered.

On the Glass First

For a curtain, the glass comes first: it's the hard surface still left bare once the panels are in place.

In custom acoustic curtains, fabric weight matters. Fullness matters just as much. Fullness is how much fabric is gathered relative to the width it covers.

NRC, like its metric equivalent αw, is an absorption coefficient from 0 to 1: the share of sound the fabric absorbs instead of bouncing back. A heavy curtain hung flat measures an NRC around 0.35. Gathered to about 200% fullness, the same fabric reaches around 0.60. Flat, it absorbs roughly half as much.

The plenum, meanwhile, is the air gap between the fabric and the glass or wall. In a reference test by the PTB laboratory, a gathered fabric hung 15 cm off the wall reached an αw of 1.00. That places it in Class A of the ISO 11654 standard, the highest rating for absorption.

A ceiling track can be recommended, since its position sets that plenum. You or your installer mount it, and Nalia sews the curtains to the exact drop and the fixing you plan.

A curtain absorbs the mid and high frequencies well, the bass poorly: it's the chatter it softens. This heavy curtain has nothing to do with the café curtain for the storefront window, light and made for daytime.

Banquettes, Alcoves and the Private Room

After the glass, a curtain earns its place near the tables: along a banquette or at the entrance to an alcove, right where people talk.

These surfaces throw back early reflections: the voice hits the wall once before it reaches the ear. That reflection arrives so fast the ear fuses it with the voice, up to about 40 milliseconds for speech. It still colours the sound, through comb filtering: certain frequencies cancel out. Fabric on that wall softens it.

For a group, a fabric room divider marks off a private room and puts fabric between that table and the main dining room. The fabric damps the sound without stopping it. A divider is not a wall.

A curtain doesn't make a room silent. Its goal is more modest, and more useful: people can hear each other at the table.

What a Curtain Won't Do

A curtain doesn't fix noise at its source, and it doesn't stop sound passing through walls. It works inside the room, and only there.

• The kitchen, through the pass window: that noise arrives directly, and absorbing sound in the dining room doesn't cut it at the source.
• Ventilation: a range hood or an air conditioner is a mechanical source, addressed at the unit. A curtain won't quiet a fan.
• The music you chose: a curtain doesn't turn down the volume. Played loud, it makes your guests raise their voices and restarts the Lombard-effect loop.
• The bass: a curtain a few centimetres thick does little below about 300 Hz. Absorbing 50 Hz properly would take an absorber about 1.7 m deep. The article on listening rooms and home theatres explains why.
• Upstairs or next door: fabric is too light to stop that sound. A heavy curtain weighs 5 to 10 times less per square metre than the glass it covers, and air moves right past its edges.

Soundproofing a restaurant is a different job: keeping sound from passing into another space, through the ceiling or a shared wall. It relies on the mass and airtightness of the construction, SONOpan's territory. A curtain instead damps sound inside the room: a different mechanism, a different rating, NRC rather than STC. Knowing which job you're actually asking a curtain to do, absorption or isolation, is what keeps expectations honest.

Fire, Cleaning and Hygiene

In a restaurant, a curtain carries obligations a curtain at home doesn't: its fabric is chosen for fire and maintained for grease.

Flame Resistance

A restaurant's curtains are subject to a flame-resistance requirement.

The National Fire Code, a model code whose text provinces such as Ontario reproduce, refers to the CAN/ULC-S109 standard for drapes and curtains in assembly occupancies. Its conditions target exits, their access routes and the number of people admitted.

In Quebec, the Règlement sur la sécurité dans les édifices publics cites an older test standard, and which standard currently succeeds it isn't confirmed. So confirm the requirement that applies to your room with your municipality's fire department or your insurer.

Choose a fabric that's inherently flame-resistant. The resistance sits in the fibre and survives cleaning. A surface-applied treatment can wash out after the very first cleaning, and even dry-cleaning solvents can strip it. The same commercial constraints apply to any restaurant's curtains beyond fire alone.

Cleaning in Food Service

A restaurant's heavy curtain gets dry-cleaned, about once a year. Velvet, wool and interlined curtains go to the cleaner, not the washing machine. In water, a heavy drape shrinks 5 to 10% and no longer falls to the planned length. A light, unlined curtain, on the other hand, can take a delicate wash.

Why every year? In food service, fabric traps grease, smoke residue and odours. Those deposits oxidize and weaken the fibres from the inside, even when the curtain still looks clean.

That schedule comes from On-Site Drapery Cleaner, a commercial drapery cleaner in Ontario. It's trade practice, not a regulation.

Nalia's Sherbrooke workshop also offers curtain cleaning and pressing.

Getting Your Room Measured in the Townships

In the Eastern Townships, everything starts with a visit to your room, not a purchase.

If your bistro faces Wellington Street or King Street in Sherbrooke, with tall storefront windows, Nalia comes to measure on site. Same thing if your café is in Magog, or your dining room occupies an old house in North Hatley.

Ideally she comes during service. Empty, a room gives away nothing about its noise. Nalia measures the glazing, notes the hard surfaces and watches the staff's path between the kitchen and the tables. She also spots where the fabric will stack once the curtains are open. She then sews the curtains in her workshop.

On your side, photograph the room at its loudest hour. Take stock of the ceiling and the walls: already treated, planned, or off-limits. Whatever's already done changes what's left to cover. Finally, check whether the building allows a ceiling track to be mounted, and who will install it: you or your installer.

The production lead time isn't set before the visit. Add it to the list of questions you'll ask that day.

Frequently Asked Questions

How many curtains for a 40-seat room?

Seat count doesn't tell you: glazed area does. Add to that the hard surfaces still left once the ceiling and walls are treated. Nalia measures the room on site, and no number of curtains is promised in advance. The tape measure counts, not the chairs.

Does this replace an acoustic ceiling?

No. The ceiling comes first, the walls second, and curtains take the glazing that panels can't cover. They absorb the mid and high frequencies well, but very little bass. A curtain completes a treated ceiling, it doesn't replace it.

Do the curtains need to be closed to work?

To treat the glass, yes, during the noisy evening service. A curtain absorbs where it hangs: open and stacked to the sides, it leaves the bare glass to bounce sound back. Closed, it covers the glazing. It also needs to keep its folds, because pulled flat, the same heavy fabric absorbs roughly half as much.

Do curtains need to be flame-resistant in a restaurant?

Yes: a restaurant's curtains are subject to a flame-resistance requirement. In Quebec, to find out which one applies to your room, contact your municipality's fire department or your insurer. Choose a fabric that's inherently flame-resistant, for the reasons given earlier in the fire section. Confirm the requirement first, choose the fabric after.

Where to Start

Start by measuring your room at peak hour, an evening when every table is taken. Even a rough reading comes before any spending, and it costs nothing but a few minutes at the busiest table in the house.

For a noisy restaurant, keep the order: the ceiling, the walls, then curtains on the glass. Skipping the ceiling asks the curtain to do another fix's job.

Once the ceiling and walls are handled or planned, browse Nalia's commercial services before requesting a quote for your glazing. And call before the season starts. Nalia sews the curtains in her Sherbrooke workshop, and they're better hung before your room is full every night.