%0 Journal Article
%T Scan and Paint: Theory and Practice of a Sound Field Visualization Method
%A Daniel Fern¨˘ndez Comesa£ża
%A Steven Steltenpool
%A Graciano Carrillo Pousa
%A Hans-Elias de Bree
%A Keith R. Holland
%J ISRN Mechanical Engineering
%D 2013
%R 10.1155/2013/241958
%X Sound visualization techniques have played a key role in the development of acoustics throughout history. The development of measurement apparatus and techniques for displaying sound and vibration phenomena has provided excellent tools for building understanding about specific problems. Traditional methods, such as step-by-step measurements or simultaneous multichannel systems, have a strong tradeoff between time requirements, flexibility, and cost. However, if the sound field can be assumed time stationary, scanning methods allow us to assess variations across space with a single transducer, as long as the position of the sensor is known. The proposed technique, Scan and Paint, is based on the acquisition of sound pressure and particle velocity by manually moving a P-U probe (pressure-particle velocity sensors) across a sound field whilst filming the event with a camera. The sensor position is extracted by applying automatic color tracking to each frame of the recorded video. It is then possible to visualize sound variations across the space in terms of sound pressure, particle velocity, or acoustic intensity. In this paper, not only the theoretical foundations of the method, but also its practical applications are explored such as scanning transfer path analysis, source radiation characterization, operational deflection shapes, virtual phased arrays, material characterization, and acoustic intensity vector field mapping. 1. Introduction In the development of acoustics, sound representations have been thought of as a key to aid in its understanding. The necessity to represent sound and vibration information visually triggered many investigations with a common goal: to create tools to build intuition and understanding upon specific problems. Many alternative methods and apparatus have been proposed over time [1] as is addressed in the following section. Nevertheless, the current measurement procedures for characterizing sound fields can be classified by three major categories, regardless of the postprocessing techniques applied: step-by-step, simultaneous, and scanning measurements. Each of these techniques can be evaluated simply using three main features: measurement time, flexibility, and total cost of the equipment. Step-by-step is the most common technique to create spatial representations of stationary sound fields. It is based upon the acquisition of data at a set of discrete positions. The flexibility of this method is one of its main advantages since the number of transducers and their spatial distribution are completely customizable. The
%U http://www.hindawi.com/journals/isrn.mechanical.engineering/2013/241958/