Designing a restaurant or bar with acoustic treatment: why, how and what it costs

Every hospitality space has a sound, even when no music is playing. It is made of guests' voices, chairs moving, crockery, ventilation, refrigeration compressors and the coffee grinder. That sound reflects off walls, ceiling and floor and creates a feeling the guest cannot name but uses to decide whether to come back.

Acoustics is the only part of an interior that acts on every guest for the whole of their visit and that nobody notices until it is done badly.

Why it is worth doing

A guest who cannot hear leaves earlier

As background noise rises, people automatically raise their voices to stay intelligible. Every raised voice is a new noise source for the next table. The system drives itself upwards until conversation becomes an effort.

The consequence is not just discomfort: average dwell time falls, fewer drinks are ordered after the main course, and the share of guests ordering dessert or coffee drops.

Staff work in it for eight hours

A guest spends an hour and a half in a noisy room; staff spend a whole shift. Sustained exposure means fatigue, more mistakes with orders and higher turnover. In the European framework, workplace noise is governed by Directive 2003/10/EC.

What is measured and the targets

Reverberation time

The basic quantity is reverberation time (T30, RT60): the time for sound pressure to fall by sixty decibels, measured to EN ISO 3382-2.

Space	Target
Restaurant	0.6–0.8 s
Cafe	0.6–0.9 s
Bar with a musical identity	0.8–1.1 s
Hotel conference space	0.5–0.7 s
Club	Low frequencies matter more

The German standard DIN 18041 gives recommended values by volume and use: a larger room tolerates a longer decay. The figure of 0.6–0.8 s is a starting point for a room of ordinary size, not a rule for every project.

Speech intelligibility

The STI index is defined in IEC 60268-16 and runs from 0 to 1: below 0.45 poor, 0.45–0.60 fair, 0.60–0.75 good, above 0.75 excellent. In a restaurant, values above 0.60 mean two people can understand each other without effort.

Background noise levels

• Cafe, morning service: 55–60 dB(A).
• Restaurant, evening service: 65–70 dB(A).
• Bar: 75–85 dB(A).
• Club: above 90 dB(A).

What creates the problem

• Glass. A glazed facade on two walls means sound bounces back and forth between them.
• Concrete and smooth plaster. Exposed concrete is acoustically the hardest material in a room.
• Ceramic and stone floors.
• Tables without cloths and chairs with hard seats.
• Metal ceilings and exposed services.

Parallel smooth walls create flutter echo. Domed ceilings focus sound, which means one table is markedly louder than another two metres away.

Ventilation, refrigeration compressors, the ice machine, the dishwasher and the grinder together form a constant level that raises the baseline for everything else. This part is often the cheapest to fix and the most frequently overlooked.

Materials

The absorption coefficient alpha runs from 0 to 1 and depends on frequency. Measurement follows EN ISO 354; classification into classes A to E follows EN ISO 11654.

• A single NRC figure hides the frequency response. A material excellent at 2000 Hz and poor at 250 Hz will quieten crockery but not male voices.
• Speech sits between 250 and 4000 Hz, with its carrying energy around 500–1000 Hz.
• Thickness determines low-frequency performance. Ten millimetres of felt will do nothing below 500 Hz.
• An air gap behind a panel acts as extra thickness.

Porous absorbers are the basis: mineral wool, polyester fibre, acoustic foam, textile. Perforated panels allow the look of a timber ceiling while retaining absorption. Membrane absorbers work in the low range. Concealed absorbers — heavy curtains, upholstered banquettes, textile panels, rugs — are often the only acceptable route in venues with a strong visual concept.

Hospitality also demands fire classification to EN 13501-1 (usually class B or C in public spaces), cleanability and grease resistance, and moisture resistance beside the wash-up and in coastal venues.

How the design process runs

1. Survey and measurement. The actual reverberation time is measured at several points; geometry and all materials are recorded.
2. Calculation and target. The classical basis is the Sabine equation; for strongly uneven absorption, the Eyring variant.
3. Modelling. EASE calculates sound pressure distribution and speech intelligibility point by point. Absorption is placed where it contributes most, which means less material for the same result.
4. Coordination with the design. Not concessions from one side, but equivalent substitutions: if a ceiling panel is unacceptable, the shortfall is made up with walls, curtains, banquettes or acoustic render.
5. Specification. Type and quantity by surface, method of fixing including air gaps, fire classification.
6. Installation and inspection. Checks that the specified material was installed as specified and that air gaps were maintained.
7. Verification measurement and tuning. An empty room and a full room are acoustically two different spaces.

What it costs

As a pre-survey rule: a room with hard surfaces and a reverberation time of about 1.4–1.6 s needs treatment on roughly 30 to 45 per cent of the floor area. At 3 metres height that means 30 to 45 m² of material per 100 m² of floor; at 4.5 metres, 45 to 65.

Venue	Treatment	Total
250 m²	45–65 m²	3,500–12,000 EUR
500 m²	100–150 m²	8,000–28,000 EUR
1000 m²	200–300 m²	25,000–90,000 EUR

Price bands for material with installation run from 35–60 EUR per m² (basic) through 60–110 (mid) and 110–200 (higher) to above 200 for special solutions. The design element — survey with measurement, calculation, modelling and specification — runs between 800 and 2,500 EUR for a venue of ordinary size.

How we work

Our starting point is not hospitality venues but halls: multi-purpose halls with three to five hundred seats, theatres with a stage, concert spaces, conference rooms and sports facilities. These are spaces where speech intelligibility is the measure of success and where the tolerance is narrower than in hospitality.

• We measure before we propose. A quotation without a measured reverberation time is guesswork.
• We model before we order material. The result is less material for the same effect.
• We select materials ourselves and know them from installation.
• We treat acoustics and sound as one project.
• We come back after opening. Verification measurement and tuning are part of the job.

Recurring mistakes

• Acoustics addressed after the interior materials are chosen.
• Confusing absorption with insulation.
• Material chosen on a single figure without the frequency response.
• Fixing without an air gap.
• Absorption spread evenly rather than placed by the model.
• The room becomes too dead. Below 0.4 seconds a space is acoustically lifeless.
• Plant noise not addressed.
• Measurement only in an empty room.

Frequently asked questions

Can acoustics be improved in a trading venue?

Yes. Start with measures that need no building work: ceiling elements, heavier curtains, textile on seating, timber slats, rugs and felt pads under chair legs. The result is almost always noticeable.

Do acoustic panels solve problems with neighbours?

No. Panels govern the sound inside. Transmission is solved with mass, structural isolation and vibration isolation of equipment.

How much treatment is too much?

The limit is around 0.4 seconds. Below that the room loses its sense of space and guests feel exposed. The aim is not silence but controlled decay.

Can it be done from photographs alone?

For a rough estimate yes, for a design no. A photograph does not give the volume and does not measure reverberation time.

Conclusion

Acoustic treatment is the smallest line in a fit-out budget, and one that directly affects how long a guest stays, how much they order and whether they return.

The correct sequence is always the same: measurement, then calculation, then modelling, then coordination with the design, and only then buying material. The best moment to start is the concept design stage; the second best is today.