Short answer: when guests cannot follow the speaker, the problem is usually not loudspeaker power but the room, specifically its reverberation time and its background noise floor. Turkey's Regulation on Protection of Buildings Against Noise (Official Gazette, 31 May 2017, No. 30082) caps reverberation time in theatres, conference halls and auditoria below 1.0 second, and limits indoor noise in those spaces to 35 dBA for acoustic quality class C. Meeting rooms in office buildings are expected to sit between 0.6 and 0.8 seconds, teleconference rooms between 0.2 and 0.4. A ballroom with marble floors, glass walls and a four metre ceiling easily exceeds 2 seconds, and past that point adding watts does not add clarity. It adds overlapping reflections. What reaches the ear is two things: direct sound from the loudspeaker and reflections returning from surfaces. Turn the system up and both rise together, so the ratio between them stays where it was. To change that ratio you either move the source closer to the listener, add absorption, or lower the noise floor. Below: what the regulation asks for room by room, a three minute check with the Sabine formula, background noise limits, the STI figure to write into a technical spec, and five fixes that work without changing venue.
Is the loudspeaker the problem, or the room?
The symptom tells you which. If word endings disappear and syllables pile on top of each other toward the back of the hall, that is reverberation. If speech is clear but sits under a constant hum, that is noise. The physics differ. Direct sound weakens with distance while the reverberant field stays roughly constant throughout the room, so beyond a certain distance reflections dominate. Turning the system up does not shift that balance. The pattern shows up at almost every long hall: the first ten rows are fine, the middle of the room starts losing the presentation, and the crew tries to fix it with level. Higher level also feeds the reverberant field, so the room gets worse. The fix is to move the source closer and reduce reflected energy, not to add boxes.
What does the regulation ask for, second by second?
The Turkish regulation defines reverberation time as the time needed for sound pressure level to fall by 60 dB after a source in the room stops. Annex E, Table E.2 sets limits per room type. Theatres, conference halls and auditoria must stay below 1.0 second. Cinemas are held to 0.2 to 0.4 seconds, meeting rooms in office buildings to 0.6 to 0.8, teleconference rooms to 0.2 to 0.4, restaurants and dining areas to 0.6 to 0.9. Sports halls and shopping centres are allowed up to 2.0 seconds, which is exactly why those spaces fight you on speech. Article 17 sets the quality threshold: new buildings must reach at least class C, and buildings undergoing major renovation at least class D. The same article requires ceiling finishes with a noise reduction coefficient of at least 0.75 in education, healthcare, offices, restaurants and canteens, all circulation areas, libraries, terminals, public facilities and sports halls. Cultural venues are not on that ceiling list, so for concert and conference halls the control sits on reverberation time itself.
Run the Sabine check before you sign
The classic method is the Sabine formula: reverberation time equals 0.161 times the volume divided by total absorption area, with volume in cubic metres and absorption in square metre sabins. Take a ballroom 20 by 15 metres with a 4 metre ceiling, so 1,200 cubic metres. Holding reverberation under 1.0 second needs 0.161 times 1,200, roughly 193 square metre sabins of absorption. Total surface area is 880 square metres. Across marble, plaster and glass the average absorption coefficient sits near 0.1, which gives 88 square metre sabins and a reverberation time close to 2.2 seconds. In a hall whose ceiling carries an acoustic finish at 0.75 NRC, the ceiling alone contributes 225 square metre sabins and the same calculation lands at 0.9 seconds. On a rental production you cannot touch the ceiling, so the difference has to come from carpet, drape and upholstered seating. Existing rooms can be measured instead of estimated: the regulation cites TS EN ISO 3382-2 for ordinary rooms and TS EN ISO 3382-1 for performance spaces. A single hand clap in the middle of an empty hall already tells you whether you need to plan drape.
How quiet does the room need to be?
Annex E, Table E.1 of the same regulation caps indoor noise. For theatres, conference halls and auditoria the equivalent noise level allowed is 35 dBA in class C and 30 dBA in class A. Concert halls are far tighter at 25 dBA for class C. Meeting rooms in office buildings sit at 35 dBA, shopping centres at 55 dBA. For comparison, the American classroom standard ANSI/ASA S12.60 limits background noise to 35 dBA and reverberation to 0.6 seconds in core learning spaces up to 283 cubic metres, with the reverberation limit rising to 0.7 seconds between 283 and 566 cubic metres. Three sources wreck those figures on site: air handling units, fans in LED walls and dimmer racks, and the programme running in the hall next door. Rehearsing with the air conditioning switched off and handing over a full room with everything running is the most repeated mistake in the business. Evacuation depends on the noise floor too. Article 81 of Turkey's fire protection regulation requires audible warning devices to run at least 15 dBA above the average ambient level, measured 150 centimetres above the floor.
Write STI into the spec, not watts
Speech transmission index, or STI, folds reverberation and noise into a single number. IEC 60268-16 defines it and splits the scale into qualification bands tied to use cases. Above 0.70 covers theatres and speech auditoria, 0.66 to 0.70 teleconference, 0.62 to 0.66 classrooms, and 0.50 to 0.58 public address in shopping malls. Values below 0.42 are treated as unsuitable for public address. Measurement takes minutes on site with a STIPA test signal, repeated at several points across the seating area. That is how you turn a vague clarity expectation into a contractual target. On a conference with heavy speech content, specify a minimum STI across the whole audience area, and the post load-in conversation rests on a measurement rather than on opinion.
Five fixes that work without changing venue
One: shorten the distance to the listener. In a long room, a delay line at mid hall buys direct sound that pushing the stage system never will. Two: control directivity. A line array with tight vertical coverage, or a point source box aimed with the right tilt, puts energy on seats instead of the back wall and the ceiling. Energy that misses the audience comes back as reflection. Three: level discipline. Application notes from measurement equipment makers put best announcement intelligibility in the 70 to 80 dB sound pressure range, and going far above that lifts the reverberant field along with the direct sound. Four: microphone choice. Lavalier and over ear capsules work close to the source, so they raise signal to noise ratio and widen feedback headroom. A presenter holding a handheld twenty centimetres from the chin will defeat any system. Five: add soft surfaces. Pleated drape on rear and side walls, stage carpet, upholstered chairs and the crowd itself all pull reverberation down, which is why an empty room in rehearsal sounds worse than the same room full.
Six questions for the site visit
One: does the building have an acoustic design or an architectural acoustics report? The regulation requires sound insulation in permitted buildings to follow the acoustic design, and newer venues usually hold the document on file. Two: has the hall's reverberation time been measured, and at which frequencies? Three: what is the NRC of the ceiling finish? Four: what is the noise level in dBA with the air conditioning at full capacity? Five: is there a programme in the adjoining hall on the same day, and what is the insulation of the movable partition between them? Article 19 requires insulation values to be established by calculation in rooms with sound reinforcement, yet operable partitions rarely match fixed construction. Six: are there rigging points for delay speakers and drape, and who signs off the load? Those six answers tell you whether the room suits speech before the venue contract is signed.
Set the target by programme type
A speech heavy congress wants short reverberation and a low noise floor: under 1.0 second, 35 dBA, and a measured STI across the seating area. A gala night with a live band changes the brief, because a fully dead room makes music sound lifeless, so the balance gets struck around the spoken segments at the top of the show. Mixed formats such as award nights need two approaches in one design: close and tightly aimed for speech, broad coverage for music. Accessibility belongs in this conversation as well. The World Health Organization's World Report on Hearing, published in March 2021, estimates that around 1.5 billion people currently live with some degree of hearing loss, and projects nearly 2.5 billion by 2050, roughly one person in four. For part of your guest list, intelligibility is not comfort, it is the condition for following the programme at all. Tales Event works out of Istanbul and delivers sound, staging, lighting, LED screens and simultaneous interpretation for congresses, dealer meetings, launches, gala nights and opening ceremonies across Turkey. Send us your room dimensions and the run of show, and we will come back with a reverberation target, a loudspeaker layout and a drape plan where the room needs one.
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