Introduction: Concept And Definition Of A Line Array System - Ecler BET ACOUSTICS MASS1015P Manual De Instrucciones

2. INTRODUCTION: CONCEPT AND DEFINITION OF A LINE ARRAY SYSTEM

LINE ARRAY: "A group of emitting elements placed close together in a straight line, emitting with
the same phase and amplitude". As per Harry F. Olson in his work "Acoustical Engineering and
Dynamical Analogies" (New York, 1940
Currently the advantages of line array systems over conventional sound equipment are common
knowledge: greater control of auditive coverage level, increased performance, greater projection,
optimisation of frontal emission and also lower weight and volume to handle.
The purpose of the following sections of this user manual is to provide a simplified view of the
behaviour of line array systems and familiarise the user with the basic concepts of acoustics and
electroacoustics.
2.1. Historical introduction
Although the commercial development of Line Array systems began to expand in the 90s, the
acoustic principles that govern the behaviour of line array systems date back to observations made and
parallelisms introduced more than 150 years ago in the field of acoustics after the study of the behaviour
of polarised light.
The analogy between the behaviour of both types of radiation, light and sound, makes it possible
to establish the basic theories on which are based the minimum requirements that define the behaviour
of sound amplification systems such as the line array.
To understand the advantages of a line array system over a conventional sound system it is
important to keep in mind how sound behaves from the point of view of propagation.
2.2. Sound propagation
There are three basic natural forms of propagation of sound in air, each of which has its own
characteristics as regards form and pressure level attenuation as a function of the distance of the
listener from the sound source:
a) Spherical waves
These are emitted by a point source of sound which sends out a
spherical wave front, which therefore obey the inverse square law:
In this case, the level of sound pressure is attenuated by 6dB SPL for
each doubling of the distance between the listener and the sound
source in open air.
b) Cylindrical waves
These are emitted by a line of juxtaposed sound sources. The sound
emission of the group behaves as a cylindrical wave front with
attenuation with respect to the sound source of 3dB SPL.
Basically with a line array system the behaviour of the wave front for
a given range of frequencies follows this type of propagation so long
as the listener is located within the so-called near field (see section
2.3.).
The propagation of cylindrical waves is clearly advantageous as compared with the type of
propagation of spherical waves.
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