Scan-Based Sound Visualization Methods using Sound Pressure and Particle Velocity (original) (raw)

Scan and Paint: Theory and Practice of a Sound Field Visualization Method

ISRN Mechanical Engineering, 2013

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...

Mapping stationary sound fields using scanning techniques: the fundamentals of Scan & Paint

Scanning measurement techniques such as "Scan & Paint" have been shown to improve upon the performance of traditional methods in terms of flexibility, measurement time and cost as long as the sound field can be assumed time stationary. The method is based on the acquisi-tion of sound pressure and particle velocity by manually moving a PU probe across a sound field while filming the event with a camera. The sensor position is extracted by applying au-tomatic color tracking to each frame of the recorded video. It is then possible to visualize sound variations across the space in terms of pressure, particle velocity or sound intensity. Several algorithms can be applied for mixing spatial information with the acoustic signals. This paper introduces the two main algorithms developed: the point method and the grid method. For this purpose, not only the theoretical foundations of both methods are explored but also their practical implications as efficient sound visualization tech...

Direct acoustic vector field mapping: new scanning tools for measuring 3D sound intensity in 3D space

One of the main challenges arising from noise and vibration problems is how to identify the areas of a device, machine or structure that produce signicant acoustic excitation. Measurement methods relying on sound intensity are widely used for the localization and quantication of noise sources although they are often limited by the measurement environment. In contrast, the use of a microphone in combination with three orthogonal particle velocity sensors enables the direct acquisition of 3D dimensional sound intensity without the traditional frequency constrains of pressure-based solutions. Furthermore, stationary sound elds can be characterized eciently by means of manual scanning techniques. In this paper, a expanded scanning method is used in combination with a 3D tracking system based on a stereo camera. Acoustic variations throughout space can be then determined by combining the signals acquired with the tracking information of the probe. An overview of the measurement methodology is given along with the evaluation of several practical examples.

Spatial resolution limits for the localization of noise sources using direct sound mapping

2016

One of the main challenges arising from noise and vibration problems is how to identify the areas of a device, machine or structure that produce significant acoustic excitation, i.e. the localization of main noise sources. The direct visualization of sound, in particular sound intensity, has extensively been used for many years to locate sound sources. However, it is not yet well defined when two sources should be regarded as resolved by means of direct sound mapping. This paper derives the limits of the direct representation of sound pressure, particle velocity and sound intensity by exploring the relationship between spatial resolution, noise level and geometry. The proposed expressions are validated via simulations and experiments. It is shown that particle velocity mapping yields better results for identifying closely spaced sound sources than sound pressure or sound intensity, especially in the acoustic near-field.

Real‐time visualization of acoustic wave fronts by using a two‐dimensional microphone array

The Journal of the Acoustical Society of America, 1988

This article describes a real-time visualization,system for sound fields. The system includes a twodimensional microphone array (8 X 8), which eliminates the need for mechanically scanning the microphone and enables real-time processing. Three methods are tested for drawing interpolated images of sound fields from the sparse sampling points. A frequency-detection circuit is introduced to show the direction of sound propagation stroboscopically. Superposition of visualized sound wave fronts on the video picture of the field helps one to understand the sound fields present.

A scanning method for source visualization and transfer path analysis using a single probe

There are several methods to capture and visualize the acoustic properties in the vicinity of an object. This article considers scanning PU probe based sound intensity and particle velocity measurements which capture both sound pressure and acoustic particle velocity. The properties of the sound field are determined and visualized using the following routine: while the probe is moved slowly over the surface, the pressure and velocity are recorded and a video image is captured at the same time. Next, the data is processed. At each time interval, the video image is used to determine the location of the sensor. Then a color plot is generated. This method is called the Scan and Paint method. Since only one probe is used to measure the sound field the spatial phase information is lost. It is also impossible to find out if sources are correlated or not. This information is necessary to determine the sound pressure some distance from the source, at the driver's ear for example. In this...

Visualization of reflected sound in enclosed space by sound intensity measurement

Acoustical Science and Technology, 2006

To examine the relationship between surface scattering and the properties of sound field, visualization technique based on the sound intensity measurement is introduced. Measurement of the impulse responses at closely located four points yield the intensity response in three orthogonal directions. Dominant peaks in the intensity response could be recognized as the dominant reflections from the certain room surface. Our method projects such information onto the spherical panoramic photo of the field. In addition to such qualitative visualization, quantitative examination is also tried. We have introduced here the index called uniformity of arrival directions, UAD, as one measure of sound field. The UAD is defined by the temporal changes of uniformity of arriving directions of reflections and is calculated by the intensity levels observed at equally divided solid angles on the surface of imaginary sphere around the measurement point.

Acoustic visualizations using surface mapping

2014

Sound visualizations have been an integral part of room acoustics studies for more than a century. As acoustic measurement techniques and knowledge of hearing evolve, acousticians need more intuitive ways to represent increasingly complex data. Microphone array processing now allows accurate measurement of spatio-temporal acoustic properties. However, the multidimensional data can be a challenge to display coherently. This letter details a method of mapping visual representations of acoustic reflections from a receiver position to the surfaces from which the reflections originated. The resulting animations are presented as a spatial acoustic analysis tool.

Acoustic Intensity Imaging Methods for in-situ Wave Propagation

Archives of Acoustics, 2010

In the paper the author has described the visualization methods in acoustic flow fields and show how these methods may assist scientists to gain understanding of complex acoustic energy flow in real-life field. A graphical method will be presented to determine the real acoustic wave distribution in the flow field. Visualization of research results, which is unavailable by conventional acoustics metrology, may be shown in the form of intensity streamlines in space, as a shape of floating acoustic wave and intensity isosurface in three-dimensional space. In traditional acoustic metrology, the analysis of acoustic fields concerns only the distribution of pressure levels (scalar variable), however in a real acoustic field both the scalar (acoustic pressure) and vector (the acoustic particle velocity) effects are closely related. Only when the acoustic field is described by both the potential and kinetic energies, we may understand the mechanisms of propagation, diffraction and scattering of acoustic waves on obstacles, as a form of energy image. This attribute of intensity method can also validate the results of CFD/CAA numerical modeling which is very important in any industry acoustic investigations.