Sound intensity generation in hard-walled duct with acoustic flow (no mean-flow) is treated exper... more Sound intensity generation in hard-walled duct with acoustic flow (no mean-flow) is treated experimentally and shown graphically. In paper, numerous methods of visualization illustrating the vortex flow (2D, 3D) can graphically explain diffraction and scattering phenomena occurring inside the duct and around open end area. Sound intensity investigation in annular duct gives a physical picture of sound waves in any duct mode. In the paper, modal energy analysis are discussed with particular reference to acoustics acoustic orthogonal decomposition (AOD). The image of sound intensity fields before and above "cut-off" frequency region are found to compare acoustic modes which might resonate in duct. The experimental results show also the effects of axial and swirling flow. However acoustic field is extremely complicated, because pressures in non-propagating (cut-off) modes cooperate with the particle velocities in propagating modes, and vice versa. Measurement in cylindrical duct demonstrates also the cut-off phenomenon and the effect of reflection from open end. The aim of experimental study was to obtain information on low Mach number flows in ducts in order to improve physical understanding and validate theoretical CFD and CAA models that still may be improved.
The author presents the results of acoustical tests with respect to ship floors with increased so... more The author presents the results of acoustical tests with respect to ship floors with increased sound isolating properties. The tests were carried out using a full-scale part of a superstructure. A description is given of this test-rig and its profits and limittations. To avoid some negative effects, additional test equipment is used.
In contrast to the classically described acoustical fields with acoustical pressure distributions... more In contrast to the classically described acoustical fields with acoustical pressure distributions (scalar effects), the graphical presentation of the acoustic energy flow in real-life acoustic fields as a vector mapping, can explain many particulars concerning the areas in which it is difficult to make a theoretical analysis (direct and near field, vortex flow, effects of scattering on obstacles, reflection on partitions, efficiency of acoustics barrier, etc.). With the experimental application of the sound intensity (SI) measurement method in real-life fields as well as the technique of presentation the results in a 2D and a 3D graphical form, numerous examples illustrate the results of applying the SI measurement for practical problems presented in the article. Concerning the intensity vector distribution of the real near and fare field, the paper presents the paths of the acoustic energy flow over the barriers and the form of the acoustical radiation field of vibrating structures...
The acoustic field may be described as a spatial distribution of pressure and particle velocity a... more The acoustic field may be described as a spatial distribution of pressure and particle velocity and may be represented by one vectors acoustics parameter – sound intensity (SI). Sound intensity is an energetic parameter which describes the average flow of acoustic energy (Fahy, 1995) and is extremely useful in many cases where the precise acoustic sound source characterisation is needed. Nowadays classical pressure acoustics methods have become omnipresent but its usage does not guarantee correct results in several cases. In order to obtain some reliable results the use of appropriate sound intensity probe is essential and the sensor has to be equipped with a three component acoustic particle velocity transducers and a pressure condenser microphone. The application of the sound intensity probes made possible to visualise many linear and non-linear effects in acoustic field which had never been seen before in conventional acoustics. The main problem with SI technique is its time-cons...
Flow distribution images in acoustic fields, connected with the graphical presentation of the aco... more Flow distribution images in acoustic fields, connected with the graphical presentation of the acoustic waves gives new possibilities of interpretation of dynamic phenomena occurring in real fields. Introduction of these possibilities has greatly changed the approach to examining many acoustic phenomena. It also facilitated ways to visualize the flow of acoustic energy. One of the new insight into the nature of acoustic field formation in real conditions of working sources is the sound intensity technique but laser Doppler velocimetry (LDV) can be also very useful in applications of acoustic. It is a frequent occurrence that the sound velocity measurements in real conditions may show great disparity between the theoretical assumptions of the acoustic field distribution. The disparity mainly comes from simplifications accompanying the analytical and numerical methods due to the lack of complete data concerning physical properties of an investigated object. Laser Doppler Velocimetry is...
Energy distribution images in acoustic fields, connected with the graphical presentation of the f... more Energy distribution images in acoustic fields, connected with the graphical presentation of the flow waves are a new element in acoustic metrology. Introduction of these possibilities have greatly changed the approach to examining many acoustic phenomena. The new insight into the nature of acoustic field formation in real conditions of working sources may bring application of the sound intensity method in conjunction with the graphical presentation of space vector distribution of acoustic power. Acoustic conditions in these areas are much different from the theoretical assumptions ascribed to free or diffuse field. It is a frequent occurrence that the sound intensity measurements in real conditions may show great disparity between the theoretical assumptions of the acoustic fields distribution and the actual measurements. The disparity results mainly from simplifications accompanying the analytical and numerical methods due to lack of complete data concerning physical properties of ...
In this article, the author described methods of visualizing the acoustic flow and showed how the... more In this article, the author described methods of visualizing the acoustic flow and showed how these methods can help scientists understand the complex flow of acoustic energy in a real field. A graphical method for determining the distribution of acoustic waves in a real 3D flow field will be presented. Vector imaging of acoustic events is not possible with the use of traditional metrology applied in pressure acoustics. Based on research using measurements of sound intensity and distribution of vector acoustic field by acoustic orthogonal decomposition method (SI-AOD), the article will present examples of practical applications of these analyses. The described measurement technique, including the method of graphical presentation of results, enriches the knowledge about the mechanism of the flow of acoustic energy stream in real working conditions of the source. The SI-AOD analysis system sets a milestone in the monitoring of sound landscapes and the precise finds noise sources.
Sound intensity generation in hard-walled duct with acoustic flow (no mean-flow) is treated exper... more Sound intensity generation in hard-walled duct with acoustic flow (no mean-flow) is treated experimentally and shown graphically. In paper, numerous methods of visualization illustrating the vortex flow (2D, 3D) can graphically explain diffraction and scattering phenomena occurring inside the duct and around open end area. Sound intensity investigation in annular duct gives a physical picture of sound waves in any duct mode. In the paper, modal energy analysis are discussed with particular reference to acoustics acoustic orthogonal decomposition (AOD). The image of sound intensity fields before and above "cut-off" frequency region are found to compare acoustic modes which might resonate in duct. The experimental results show also the effects of axial and swirling flow. However acoustic field is extremely complicated, because pressures in non-propagating (cut-off) modes cooperate with the particle velocities in propagating modes, and vice versa. Measurement in cylindrical duct demonstrates also the cut-off phenomenon and the effect of reflection from open end. The aim of experimental study was to obtain information on low Mach number flows in ducts in order to improve physical understanding and validate theoretical CFD and CAA models that still may be improved.
The author presents the results of acoustical tests with respect to ship floors with increased so... more The author presents the results of acoustical tests with respect to ship floors with increased sound isolating properties. The tests were carried out using a full-scale part of a superstructure. A description is given of this test-rig and its profits and limittations. To avoid some negative effects, additional test equipment is used.
In contrast to the classically described acoustical fields with acoustical pressure distributions... more In contrast to the classically described acoustical fields with acoustical pressure distributions (scalar effects), the graphical presentation of the acoustic energy flow in real-life acoustic fields as a vector mapping, can explain many particulars concerning the areas in which it is difficult to make a theoretical analysis (direct and near field, vortex flow, effects of scattering on obstacles, reflection on partitions, efficiency of acoustics barrier, etc.). With the experimental application of the sound intensity (SI) measurement method in real-life fields as well as the technique of presentation the results in a 2D and a 3D graphical form, numerous examples illustrate the results of applying the SI measurement for practical problems presented in the article. Concerning the intensity vector distribution of the real near and fare field, the paper presents the paths of the acoustic energy flow over the barriers and the form of the acoustical radiation field of vibrating structures...
The acoustic field may be described as a spatial distribution of pressure and particle velocity a... more The acoustic field may be described as a spatial distribution of pressure and particle velocity and may be represented by one vectors acoustics parameter – sound intensity (SI). Sound intensity is an energetic parameter which describes the average flow of acoustic energy (Fahy, 1995) and is extremely useful in many cases where the precise acoustic sound source characterisation is needed. Nowadays classical pressure acoustics methods have become omnipresent but its usage does not guarantee correct results in several cases. In order to obtain some reliable results the use of appropriate sound intensity probe is essential and the sensor has to be equipped with a three component acoustic particle velocity transducers and a pressure condenser microphone. The application of the sound intensity probes made possible to visualise many linear and non-linear effects in acoustic field which had never been seen before in conventional acoustics. The main problem with SI technique is its time-cons...
Flow distribution images in acoustic fields, connected with the graphical presentation of the aco... more Flow distribution images in acoustic fields, connected with the graphical presentation of the acoustic waves gives new possibilities of interpretation of dynamic phenomena occurring in real fields. Introduction of these possibilities has greatly changed the approach to examining many acoustic phenomena. It also facilitated ways to visualize the flow of acoustic energy. One of the new insight into the nature of acoustic field formation in real conditions of working sources is the sound intensity technique but laser Doppler velocimetry (LDV) can be also very useful in applications of acoustic. It is a frequent occurrence that the sound velocity measurements in real conditions may show great disparity between the theoretical assumptions of the acoustic field distribution. The disparity mainly comes from simplifications accompanying the analytical and numerical methods due to the lack of complete data concerning physical properties of an investigated object. Laser Doppler Velocimetry is...
Energy distribution images in acoustic fields, connected with the graphical presentation of the f... more Energy distribution images in acoustic fields, connected with the graphical presentation of the flow waves are a new element in acoustic metrology. Introduction of these possibilities have greatly changed the approach to examining many acoustic phenomena. The new insight into the nature of acoustic field formation in real conditions of working sources may bring application of the sound intensity method in conjunction with the graphical presentation of space vector distribution of acoustic power. Acoustic conditions in these areas are much different from the theoretical assumptions ascribed to free or diffuse field. It is a frequent occurrence that the sound intensity measurements in real conditions may show great disparity between the theoretical assumptions of the acoustic fields distribution and the actual measurements. The disparity results mainly from simplifications accompanying the analytical and numerical methods due to lack of complete data concerning physical properties of ...
In this article, the author described methods of visualizing the acoustic flow and showed how the... more In this article, the author described methods of visualizing the acoustic flow and showed how these methods can help scientists understand the complex flow of acoustic energy in a real field. A graphical method for determining the distribution of acoustic waves in a real 3D flow field will be presented. Vector imaging of acoustic events is not possible with the use of traditional metrology applied in pressure acoustics. Based on research using measurements of sound intensity and distribution of vector acoustic field by acoustic orthogonal decomposition method (SI-AOD), the article will present examples of practical applications of these analyses. The described measurement technique, including the method of graphical presentation of results, enriches the knowledge about the mechanism of the flow of acoustic energy stream in real working conditions of the source. The SI-AOD analysis system sets a milestone in the monitoring of sound landscapes and the precise finds noise sources.
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