• Development of a 3D finite element acoustic model to predict the sound reduction index of stud based double-leaf walls

      Nguyen, Van Bac; Arjunan, Arun; Wang, Chang; Mynors, Diane; Morgan, Tertia; English, Martin; University of Wolverhampton; Hadley Industries plc; University of Sussex (Elsevier, 2014-07-26)
      Building standards incorporating quantitative acoustical criteria to ensure adequate sound insulation are now being implemented. Engineers are making great efforts to design acoustically efficient double-wall structures. Accordingly, efficient simulation models to predict the acoustic insulation of double-leaf wall structures are needed. This paper presents the development of a numerical tool that can predict the frequency dependent sound reduction index R of stud based double-leaf walls at one-third-octave band frequency range. A fully vibro-acoustic 3D model consisting of two rooms partitioned using a double-leaf wall, considering the structure and acoustic fluid coupling incorporating the existing fluid and structural solvers are presented. The validity of the finite element (FE) model is assessed by comparison with experimental test results carried out in a certified laboratory. Accurate representation of the structural damping matrix to effectively predict the R values are studied. The possibilities of minimising the simulation time using a frequency dependent mesh model was also investigated. The FEA model presented in this work is capable of predicting the weighted sound reduction index Rw along with A-weighted pink noise C and A-weighted urban noise Ctr within an error of 1 dB. The model developed can also be used to analyse the acoustically induced frequency dependent geometrical behaviour of the double-leaf wall components to optimise them for best acoustic performance. The FE modelling procedure reported in this paper can be extended to other building components undergoing fluid–structure interaction (FSI) to evaluate their acoustic insulation.
    • The effects of distortion on the perception of loudness in live sound

      Durbridge, Simon E.; Hill, Adam J.; Taylor, John; University of Derby; d&b audiotechnik (Institute of Acoustics, 2015-11-12)
      Distortion is a central concern in audio production, and occurs in many parts of a live sound reinforcement system. Perceived loudness is a key principal in psychoacoustics, and may be strongly affected by factors such as spatial variance and the distinct effects of nonlinearity in the signal chain. The aim of this study is to highlight the relationship between perceived loudness, and different analytical forms of distortion which relate to how loudspeaker systems might behave. Some key factors of loudness perception and basic principles of distortion are discussed. A series of listening tests confirm that there is a relationship between loudness perception and distortion, and that this effect may vary between listeners. The results are analysed using perceptually motivated metrics such as Rnonlin and Loudness Units Full Scale. Overall, the importance of controlled compression techniques and limiting to avoid clipping are reinforced, as clipping may decrease aggregate perceived loudness and increase inter-listener variance in the live events domain.
    • Enhanced wide-area low-frequency sound reproduction in cinemas: effective and practical alternatives to current calibration strategies

      Hill, Adam J.; Hawksford, Malcolm O. J.; Newell, Philip; University of Derby; University of Essex; Acoustic Consultant (Audio Engineering Society, 2016-05-19)
      The current strategies for the low-frequency calibration of cinema sound systems are based on a flawed premise of low-frequency acoustics and psychoacoustics. This research shows that there is virtually no benefit in terms of spatiotemporal variance reduction: pre- and post-calibrated systems will exhibit equally position-dependent listening experience differences. For modern cinemas, the typical focus on room-modes when designing a low frequency calibration system is not necessary because the dimensions of the space coupled with low reverberation time results in Schroeder frequencies around 35 Hz. Above this value, effects of room-modes are not perceptible. Comb-filtering between sources and low-order reflections is the primary cause of high spatial variance. Furthermore, there is no evidence that spatial averaging techniques used for measurement and equalization are subjectively beneficial. A new approach needs to be invented.
    • Enhanced wide-area low-frequency sound reproduction in cinemas: Effective and practical alternatives to current sub-optimal calibration strategies

      Hill, Adam J.; Hawksford, Malcolm O. J.; Newell, Philip; University of Derby; University of Essex; Acoustic Consultant (Audio Engineering Society, 2015-03-06)
      This paper explores strategies for achieving accurate wide-area low-frequency sound reproduction in cinemas. Current standards for B-Chain calibration call for single channel low-frequency equalization aided by either single-point or spatially-averaged response measurements, an approach only applicable to a reasonably spatially invariant low frequency response. A holistic approach to low-frequency coverage optimization is presented exploiting subwoofer arrays, their positioning and multi point signal processing. Acoustic-field examples are presented using finite difference time-domain (FDTD) modeling software that expose a potential for superior wide-area signal reconstruction over that achieved using the current standards and recommendations.
    • The good, the bad, and the distant: soundscape cues for larval fish

      Piercy, Julius J. B.; Smith, David J.; Codling, Edward A.; Hill, Adam J.; Simpson, Stephen D.; University of Essex; University of Exeter; University of Derby (2015-11)
      Coral reef noise is an important navigation cue for settling reef fish larvae and can thus potentially affect reef population dynamics. Recent evidence has shown that fish are able to discriminate between the soundscapes of different types of habitat (e.g., mangrove and reef). In this study, we investigated whether discernible acoustic differences were present between sites within the same coral reef system. Differences in sound intensity and transient content were found between sites, but site-dependent temporal variation was also present. We discuss the implications of these findings for settling fish larvae.
    • Habitat quality affects sound production and likely distance of detection on coral reefs

      Piercy, Julius J. B.; Codling, Edward A.; Hill, Adam J.; Smith, David J.; Simpson, Stephen D.; University of Essex; University of Derby; University of Exeter (2014-12-03)
      The interwoven nature of habitats and their acoustic fingerprints (soundscapes) is being increasingly recognized as a key component of animal ecology. Natural soundscapes are crucial for orientation in many different taxa when seeking suitable breeding grounds or settlement habitats. In the marine environment, coral reef noise is an important navigation cue for settling reef fish larvae and is thus a possible driver of reef population dynamics. We explored reef noise across a gradient of reef qualities, tested sound propagation models against field recordings and combined them with fish audio grams to demonstrate the importance of reef quality in determining which reefs larvae are likely to detect. We found that higher-quality reefs were significantly louder and richer in acoustic events (transient content) than degraded reefs, and observed that sound propagated farther with less attenuation than predicted by classic models. We discuss how zones of detection of poor-quality reefs could be reduced by over an order of magnitude com-pared to healthy reefs. The present study provides new perspectives on the far reaching effects habitat degradation may have on organisms that utilize soundscapes for orientation towards or away from coral reefs, and highlights the value of sound recordings as a cost-effective reef survey and monitoring tool.