Ecler CKL Série Manuel Utilisateur page 15

Amongst others, following factors determine the degree of speech intelligibility inside a room:

Bandwidth and frequency response of the electroacoustic system.

Signal level and signal to noise ratio (S/N).

Reverberation time, RT

Room geometry.

Directivity and orientation of loudspeaker enclosures.

Coverage uniformity: Variations in sound pressure level throughout the audience are should not
exceed 3dB SPL.

Listener attitude.
As a general rule, the group of reflections arriving at the listener in the first 35 to 50ms after the direct
sound positively contribute to speech intelligibility. Conversely, reflections arriving more than 50ms later
than the direct sound will be interpreted as echoes, negatively affecting the comprehension of the
spoken message.
Following measures can be taken to enhance intelligibility:

Make sure the bandwidth of the PA system is wide enough at speech frequencies (flat response
between 250 and 12 kHz).

Minimize the distance between loudspeakers and audience.

Avoid delays greater than 50ms coming from different speakers.

Use highly directional loudspeakers in reverberant spaces.

Use a suitable equalization.
Typical equalization for speech intelligibility enhancement.
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