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A coherence-based method for unwrapping the relative phase between microphones is investigated. For broadband signals, this method has the potential to lead to more accurate intensity vector estimations using the Phase Amplitude and Gradient Estimator (PAGE) method [D. C. Thomas et al., J. Acoust. Soc. Am. 137, 3366-3376 (2015)] Simple unwrapping methods function by detecting phase jumps above a threshold value, which works well for frequencies associated with high signal coherence. However, since unwrapping for these methods is triggered by only one previous frequency data point, frequency ranges of low coherence often contain unwrapping errors. By including coherence in a phase unwrapping algorithm, these errors can be avoided. Ranges of relatively low coherence are given less weight in phase unwrapping and are checked for unwrapping errors. For broadband signals with continuous relative phase, using both the coherence and multiple data points to unwrap, frequencies associated with low coherence result in fewer unwrapping errors. Phase values for jet noise data with low coherence (<0.1) have been successfully unwrapped using this method, and have resulted in more reliable PAGE intensity estimates. This paper also investigates unwrapping in interference nulls produced by coherent, radiating sources. [ABSTRACT FROM AUTHOR]

The phase and amplitude gradient estimator (PAGE) method can be used to increase the bandwidth of complex acoustic intensity estimates obtained with multi-microphone probes. Despite the increased bandwidth, errors arise when using this method, which is based on linear least-squares gradients, in non-planar fields. Examples of non-planar fields include the acoustic near field of a radiating source or near a null in a standing-wave field. The PAGE method can be improved by increasing the number of microphones and using a Taylor expansion to obtain higher-order estimates of center pressure, pressure amplitude gradient, and phase gradient. For one-dimensional active intensity in a simulated monopole field, a four-microphone probe is shown to converge to less than 0.2 dB error at a closer distance than a two-microphone probe with the same inter-microphone spacing. For reactive intensity in a standing wave field, increasing the number of microphones improves the bandwidth, and applying a higher-order method to traditional reactive intensity estimation outperforms higher-order PAGE. [ABSTRACT FROM AUTHOR]

For a student musician, several activities during the day contribute to significant noise exposure and these activities take place in a variety of environments. From rehearsing in large spaces to practicing in small rooms to performing in concert halls, the sound levels experienced during the day are often high and varied. This study at Brigham Young University contextualizes the noise exposure in these situations by looking at full-day musician noise exposure in different activities and environments. The study also explores what effect room acoustic characteristics have on noise exposure and looks at trends in dosage received over activity duration. Variation was observed in dosages received between different instrument types. Additionally, room reverberation characteristics were found to have a probable correlation with the amount of noise exposure received. Both OSHA and NIOSH standards were used in dosage calculations and results from each standard were compared. [ABSTRACT FROM AUTHOR]

Crackling signals cannot be identified using any sound level or quality metric that relies solely on the long-term spectrum as input. In order to identify sound quality metrics that might succeed in modeling human perception of crackling and non-crackling sounds, a set of metrics sensitive to temporal properties of signals is applied to a set of signals with equivalent spectra but exhibiting varying degrees of crackle. Several methods for altering signals including some that remove crackling sound quality from an acoustic signal were drawn from previous work [Swift, Gee, Neilsen, 2014, Swift, Gee, Neilsen, 2017]. In this paper, an additional alteration which can partially remove crackle--randomizing the Fourier phase of a crackling signal in the frequency domain in selected frequency ranges--is considered. Variables from time-varying sound quality metrics such as loudness and sharpness, as well as roughness to signals exhibiting varying degrees of crackle are explored and relationships between them that can be exploited to identify crackling sounds are identified. Time-sensitive sound quality metrics can be used to discriminate between crackling and non-crackling signals and may help inform discussions of human perception of high-performance jet noise. [ABSTRACT FROM AUTHOR]