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Vibration-based sound power (VBSP) methods based on elemental radiators and measurements from a scanning vibrometer have been shown to be accurate for flat plates and cylinders. In this paper, the VBSP method is extended to account for simple curved structures, with a constant radius of curvature. Data are also presented that suggest the VBSP method is more accurate than the ISO 3741 standard for measuring sound power when significant background noise is present. Experimental results from ISO 3741 and the VBSP methods are compared for three simple curved plate structures with different radii of curvature. The results show good agreement for all three structures over a wide frequency range. The experimental results also indicate that the VBSP method is more accurate in the low frequency range where the curved plates radiated relatively little and significant background noise was present.

Research has shown that using acoustic radiation modes combined with surface velocity measurements provide an accurate method of measuring the radiated sound power from vibrating plates. This paper investigates the extension of this method to acoustically radiating cylindrical structures. The mathematical formulations of the radiation resistance matrix and the accompanying acoustic radiation modes of a baffled cylinder are developed. Computational sound power calculations using the vibration-based radiation mode (VBRM) method and the boundary element method are then compared and shown to have good agreement. Experimental surface velocity measurements of a cylinder are taken using a scanning laser Doppler vibrometer and the VBRM method is used to calculate sound power. The results are compared to sound power measurements taken using ISO 3741.

Helmholtz resonators are widely used, but classical models for the resonators, such as the lumped-element equivalent circuit, are inaccurate for most geometries. This article presents higher-order equivalent circuits for describing the resonators based on the one-dimensional wave equation. Impedance expressions are also derived. These circuits and expressions are given for various constituent resonator components, which may be combined to model resonators with curved, tapered, and straight necks. Resonance frequency predictions using this theory are demonstrated on two realistic resonators. The higher-order predictions are also applied to the theory of side branch attenuators in a duct and the theory of resonator coupling with a mode of an enclosure.

The theoretical development for computing sound power using acoustic radiation modes is well documented. However, an experimental validation and comparison with other sound power measurement standards over a wide frequency range has not been presented. This paper compares experimental results from an acoustic-radiation-modes-based sound power measurement method to results obtained using ISO 3741 in two scenarios. First, sound power measurement results from a single simply-supported baffled panel are compared. A comparison of sound power measurements of two simply-supported baffled panels is then presented. Results between the two methods for the single panel show a maximum one-third octave band difference of 2.2 dB between 200 Hz and 4 kHz with an overall difference of 1.7 dB. For the two-panel system, the maximum one-third octave band difference is 1.6 dB with an overall difference of 0.7 dB. It is also shown that in the two-panel case, the sound power from each panel can be measured individually using the acoustic radiation modes approach and summed to obtain the overall sound power as measured using ISO 3741.

A method is presented to suppress grating lobes in beamforming using phase unwrapping and array interpolation. When the phase of each cross spectrum is successfully unwrapped, the magnitude and phase of the cross spectral matrix may be interpolated; for cases where these quantities vary smoothly, interpolation is straightforward, even above the spatial Nyquist frequency. Two applications are presented: localization of a broadband source and characterization of a source with frequency-dependent location. In both cases, grating lobes are suppressed and the source is localized at frequencies up to at least 8 times the spatial Nyquist frequency.

Acoustic resonators, such as the Helmholtz resonator, provide a stable, cost effective passive noise control solution, and have been widely used to attenuate unwanted sound in enclosures and ducts. Classical formulations predicting the input impedance of such resonators often have significant error, creating a need for repeated prototyping or tuning during fabrication to achieve the desired response. Previous work found that higher-order calculations, including impedance translation and equivalent circuit modelling, produce much more accurate predictions [Calton and Sommerfeldt, J. Acoust. Soc. Am. 139, 2205 (2016)], allowing prototyping to be done quickly on a computer before fabrication of the resonators. This talk will continue the discussion in the work referenced above. In addition to resonator impedance predictions, resonator-enclosure coupling predictions will be discussed. It will be shown through comparison of predicted and experimental results that the impedance and coupling predictions can remove the need for repeated prototyping and tuning. We will also show the incorporation of these predictions into a user interface allowing engineers without acoustics background the ability to design resonators for passive noise control.

Because of the instrumentation difficulties of Fourier acoustical holography, it is desirable to find a holography method that does not require reference signals during array scanning. Among the methods that have been investigated to remove the need for references are those based on acoustic intensity measurements, including the complex-intensity-based near-field acoustical holography (CIBNAH) method [A. Nejade, J. Sound Vib. 333(16), 3598–3608 (2014); Appl. Acoust. 116, 348–356 (2017)]. The CIBNAH method has previously been applied to simple contrived sources and real-world machinery but has not been verified using analytical source models. This work shows the application of CIBNAH to an analytical model of a simply-supported plate, revealing key shortcomings of the method. The theory behind CIBNAH is discussed in light of these shortcomings. It is shown that while CIBNAH may be useful for finding radiation hot spots, it is not an adequate method to overcome the need for references in scan-based acoustical holography. [Work supported by NSF.]

Acoustic radiation modes have recently regained the attention of the literature, with applications ranging from active structural acoustic control to acoustical holography. Typically the calculation of these modes requires boundary element methods for all but flat plate and full sphere geometries. This paper presents a radiation mode formulation for cylindrically curved structures with small curvature, based on the uniform theory of diffraction. This formulation shows promise, as it produces analytical expressions for the radiation resistance matrix, leading to computationally efficient radiation mode calculation. Radiation modes are shown for cylindrically curved plates, and the calculation of sound power with these modes is compared to that calculated using boundary element methods. The extension of this formulation to other curved structures is discussed.

Acoustic radiation modes have become a useful and widespread analysis tool in situations involving sound radiation from vibrating structures. They have found use in applications such as active structural acoustic control, optimization of structures for minimal sound radiation, and acoustical holography. Analytical expressions for the radiation resistance matrix, from which the radiation modes are obtained, are available only for a small number of simple source geometries, while the obtaining of radiation modes for more complicated structures typically requires BEM or similar computational methods. This paper details the development of quasi-analytical expressions for the radiation resistance matrices of singly-curved structures such as curved plates, cylinders, and angularly truncated cylinders. It is shown that the radiation modes of these structures may be obtained with a relatively low computational load compared to conventional methods.

This paper describes the development and presentation of a Science, Technology, Engineering, Arts, and Math (STEAM) workshop for elementary school teachers designed to provide ideas and tools for using acoustics in the classroom. The abundant hands-on activities and concepts in acoustics naturally link science and music in an intuitive way that can assist teachers in moving forward on the STEAM initiative. Our workshop gave teachers an introduction to acoustics principles and demonstrations that can be used to tie in STEAM techniques with Utah State Education Core standards. These hands-on demonstrations and real-world applications provide an avenue to engage students and support learning outcomes. Feedback indicated that the participants learned from and enjoyed the initial implementation of this workshop, though many elementary school teachers did not immediately see how they could integrate it into their curriculum. While additional efforts might be made to better focus the training workshop for the K-...

This paper describes the development and presentation of a Science, Technology, Engineering, Arts, and Math (STEAM) workshop for elementary school teachers designed to provide ideas and tools for using acoustics in the classroom. The abundant hands-on activities and concepts in acoustics naturally link science and music in an intuitive way that can assist teachers in moving forward on the STEAM initiative. Our workshop gave teachers an introduction to acoustics principles and demonstrations that can be used to tie STEAM techniques in with Utah State Education Core standards. These hands-on demonstrations and real-world applications provide an avenue to engage students and support learning outcomes. Feedback indicated that the participants learned from and enjoyed the initial implementation of this workshop, though many elementary school teachers did not immediately see how they could integrate it into their curriculum. While additional efforts might be made to better focus the training workshop for the K-...