Essais & Simulations n°112

MESURES ET METHODES DE

MESURES ET METHODES DE MESURE Compte tenu du caractère international des secteurs abordés, certains articles sont écrits et publiés en anglais. Localisation des sources sonores Selecting the most appropriate sound source localization techniques for modern-day industrial applications - a number of rather standard methods, based on microphone arrays, have matured. Even though these basic techniques have undergone constant improvement, the problem remains that there is not one « magical » single sound source localization technique that prevails over the others. Depending on the test object, the nature of the sound and the actual environment, engineers will have to select one method or the other. This article reviews some of the available techniques and their recent evolutions. It helps determine which method results in the best sound sources localization for the job. Overview of sound source localization techniques accurately project the sound origin on important criteria help assess the result quality: spatial resolution and dynamic range. a technique where the microphone array is placed relatively close to the sound as the area that is closer to the sound source than one or two wavelengths of good results over the entire frequency range. However, it can only propagate sound pressure to a surface that is pa- pagation plane’s size is identical to the measured plane. further away from the source than the ming requires that all data is measured pagation does not relate to the measure- 0.5m diameter, it is possible to propagate pressure to an entire car. Results can be viewed immediately after data acquisi- - amount of time. Recent advances beamforming are focused on covering areas depicted with purple rectangles in the entire frequency range, but is limited match ½ wavelength of lowest frequen- - beamforming technique based on near - resolution by a factor of 2 over the entire frequency range. At a certain frequency limit, obtaining good results accuracy and a larger number of transducers and measurement channels, which in turn increases hardware investments and gular arrays, the problem is rewritten as in this formulation includes both propagated and evanescent wave functions, and needs an optimal and stable PCAbased regularization, which includes Selecting a technique localization technique are: frequency range of interest, distance measured to the source, physical properties of the sound source and operational conditions. First, the engineer measures the sound of the object under study with a single microphone from a relevant position, crophone spectrum, a number of critical - should be preferred, when possible, as they often provide the best results in terms of dynamic range and spatial reso- Essais & Simulations JANVIER 2013 PAGE 38

MESURES ET METHODES DE MESURE - suitable technique in the low and mid priate for higher frequencies. ray’s dimension matches the object size - dimension in turn determines the number of required microphones and measure- minimum frequency of interest. For objects that are too big to reasonably match the size of an array, it is possible to use - the condition is not stationary, it should at least be a repeatable transient condition, such as a run-up in function of rpm, or a repeatable impulsive noise, such as a door slam. not possible to measure in patches due to rapidly changing operational condi- solution will be chosen. A good strategy to get a global view on where the sound acoustic camera is moved into the near these sound sources using focalization. irregular arrays with the same data. advantage as it measures in the near and dynamic range over a wide frequen- sometimes not possible either because of physical properties or operational behavior of the object. alternative for such cases, providing results with good spatial resolution and dynamic range, depending on the frequen- results in a single shot wide-angle mea- as well as in-depth root cause analysis, Essais & Simulations JANVIER 2013 PAGE 39