To achieve an optimum sound experience in a room, it is important for speaker units and subwoofers, if any, to be dimensioned correctly in relation to the room in question.

Dimensioning - speakers
Several factors affect the sound experience in a room and must be taken into consideration when calculating the quantity and distribution of loudspeaker panels in the ceiling, to ensure as uniform a sound pressure as possible. Troldtekt will be happy to provide advice on dimensioning of loudspeaker units and to carry out measurements for project planners.

Some of the factors affecting dimensioning are:

• Speech intelligibility and sound pressure distribution
• Room geometry, particularly ceiling height
• Room reverberation time
• Background noise

Speech intelligibility and sound pressure
distribution

• A high level of speech intelligibility requires a good sound system and good room acoustics with a low reverberation time.
• A Troldtekt acoustic ceiling ensures optimum sound absorption with a low reverberation time in the room. Furthermore, the NXT technology ensures that speech emitted from the loudspeaker panels is perceived clearly and distinctly.

Geometry
At ceiling heights from 2.5 - 8 m, it would be sufficient to have one speaker panel per approximately every 30 sq m to ensure optimum speech intelligibility and good sound pressure distribution while at ceiling heights below 2.5 m, it may be necessary to increase the number of speaker panels to ensure good sound pressure distribution.

At ceiling heights above 8 m, it may be necessary to increase the number of loudspeaker panels to ensure a sufficient sound pressure. In situations with smaller requirements to sound pressure distribution or speech intelligibility, the number of loudspeaker panels can be reduced.

Reverberation time
The longer the reverberation time in the room, the fewer loudspeaker panels are required to ensure a sufficient sound pressure. However, a longer reverberation time will reduce the speech intelligibility in the room, and you should therefore strive to reduce the reverberation time below 0.6-0.9 seconds, depending on the nature of the job. The Troldtekt ceiling has high sound absorption and efficiently reduces the reverberation time in the room.

Background noise
For PA systems in particular, it is important that the sound system signal is clearly differentiated from the background noise. One way of obtaining this is to ensure a sufficiently high sound pressure to drown out background noise. Alternatively, you can ensure that the sound is evenly distributed throughout the room so that disturbing background noise does not act as a barrier between the sound source and the listener.

Subwoofers ensure optimum reproduction of the low bass frequencies below 200 Hz. For systems designed to play music, it is important for achieving good sound that the quantity of subwoofers is correct.

Normally, one subwoofer should be provided every 60-120 sq m. As directional determination of the low bass frequencies is difficult, the requirements for even distribution of the speaker panels does not apply to the subwoofers. For PA systems, which do not require the same bass volume as music systems, the number of subwoofers can be reduced – or possibly be eliminated entirely.

At ceiling heights from 2.5-8 m, it would be sufficient with one speaker panel approximately every 30 sq m to ensure optimum speech intelligibility and good sound pressure distribution.

Sound pressure and dB
Sound pressure is the generally used method for measuring the power of sound volume. The range perceivable by the human ear – from weak to pow¬erful sound pressure – is enormous, which is why the decibel scale (dB) is typically used. 0 dB is the weakest sound perceivable by the ear, while the most powerful sounds register around 120-130 dB.

Reverberation time
The reverberation time is an expression indicating how fast sound dies away in a room, e.g. clapping your hands. Specifically, it is the time (in seconds) that passes from the end of the sound impulse until the sound level has dropped by 60 dB.

Speech intelligibility
Speech intelligibility indicates how well speech is perceived in a room – either directly in the room with a speaker and a number of listeners, or via a sound system with a microphone, amplifier and speakers. In its classic form, speech intelligibility is measured by counting how many words are correctly perceived from a text read by an articulate speaker. If the listeners perceive 60% of the words correctly on average, the speech intelligibility is 60% or 0.6.