A Study On Loudspeaker Line Arrays

The research and development of loudspeaker line arrays are topics of interest in sound-reinforcement applications,as they can produce more sound power to cover a large audience area.A loudspeaker line array is designed to work as much the same as a continuous line source,which has a narrow directivity with low side lobes,and a pressure response that decreases in level at-3 dB per doubling of distance in the near field.These characteristics are valuable and have been applied in many sound-reinforcement venues.However in practical applications,a loudspeaker line array is not actually a continuous line source,because it consists of a vertical assembly of separate enclosures,and the radiating transducers do not touch each other.At high frequencies,waves with different phases lead to irregular interferences,and it becomes difficult to achieve a long distance radiation.Meanwhile side lobes appear and vary materially with both the frequency and the gap length between transducers,which is also difficult to control.As an important parameter of loudspeaker line array,Active Radiating Factor(ARF)is defined as the ratio of actual radiating length(without gaps)to the total length of each enclosure.ARF is desired to be as high as possible,so the array works as much the same as a continuous line source.This PhD thesis deals with the way how to build the model of a loudspeaker line array.Some basic principles are introduced,and several kinds of typical loudspeaker line arrays are analyzed by responses and directivity characteristics.The ARF problem is concerned in the thesis,a way of evaluating ARF by measuring on-axis frequency responses are introduced,and an optimized way of increasing ARF is also shown which deals with two types of arrangements of high-frequency waveguides by simulations and experiments.With tolerable errors,the experiment data agree well with the simulation results.