Tutorial : public engagement through audio internet experiments

This tutorial paper details experiences of four public engagement projects that have communicated acoustic science to lay audiences using web experiments. Recent developments in personal computers, the Internet and software platforms offers new and exciting opportunities for engaging publics because technologies routinely allow the reproduction of sound. The projects are psychoacoustic experiments run via the Internet (there are an increasing number of psychology experiments mediated via the web)

The optimization of profiled diffusers

Methods have been developed to produce profiled diffusers that create a large amount of diffusion. The methods are iterative and required the development of a new parameter to measure diffusion. Achieving scattering independent of angle has been attempted over a wide bandwidth. The methods are also applicable to other diffusion criteria. The diffusers consists of a series of wells of the same width but of different depths similar to Schroeder diffusers. Applications include concert halls, theatres, and studio monitor rooms. The new diffusers have been shown to create better, more uniform diffusion than the previous designs of Schroeder. This is due to the new designs being reliant on accurate boundary element prediction methods rather than more approximate techniques

The effect of visual stimuli on the horribleness of awful sounds.

A mass web-based experiment has been carried out to explore people’s perception of horrible sounds. The advantage of a web-based methodology is that it enables hundreds of thousands of judgements to be obtained over a diverse population. As part of the project, the effect of what people saw on the screen on how they rated the sounds was examined. The sounds were auditioned with images that were either associated or unassociated with the sounds. It was found that images often affected how horrible the sound was perceived to be. For example, the image of finger nails on a blackboard made the associated sound more awful. However, in the case of disgusting sounds, such as the sound of someone eating, the images used had no significant effect on voting behaviour. The colour of the website was also varied. The hue of the website was found to be a significant factor, with a red website making the sounds less horrible than a blue/green website. The brightness and saturation of the website also altered people’s perceptions, with the brighter, more saturated website making the most awful sounds, such as the sound of someone vomiting, less horrible

Acoustic iridescence

An investigation has been undertaken into acoustic iridescence, exploring how a device can be constructed which alter sound waves, in a similar way to structures in nature that act on light to produce optical iridescence. The main construction had many thin perforated sheets spaced half a wavelength apart for a specified design frequency. The sheets create the necessary impedance discontinuities to create backscattered waves, which then interfere to create strongly reflected sound at certain frequencies. Predictions and measurements show a set of harmonics, evenly spaced in frequency, for which sound is reflected strongly. And the frequency of these harmonics increases as the angle of observation gets larger, mimicking the iridescence seen in natural optical systems. Similar to optical systems, the reflections become weaker for oblique angles of reflection. A second construction was briefly examined which exploited a metamaterial made from elements and inclusions which were much smaller than the wavelength. Boundary element method predictions confirmed the potential for creating acous- tic iridescence from layers of such a material.(C) 2011 Acoustical Society of America

A transient boundary element method model of Schroeder diffuser scattering using well mouth impedance

Room acoustic diffusers can be used to treat critical listening environments to improve sound quality. One popular class is Schroeder diffusers, which comprise wells of varying depth separated by thin fins. This paper concerns a new approach to enable the modelling of these complex surfaces in the time domain. Mostly, diffuser scattering is predicted using steady-state, single frequency methods. A popular approach is to use a frequency domain Boundary Element Method (BEM) model of a box containing the diffuser, where the mouth of each well is replaced by a compliant surface with appropriate surface impedance. The best way of representing compliant surfaces in time domain prediction models, such as the transient BEM is, however, currently unresolved. A representation based on surface impedance yields convolution kernels which involve future sound, so is not compatible with the current generation of time-marching transient BEM solvers. Consequently, this paper proposes the use of a surface reflection kernel for modelling well behaviour and this is tested in a time domain BEM implementation. The new algorithm is verified on two surfaces including a Schroeder diffuser model and accurate results are obtained. It is hoped that this representation may be extended to arbitrary compliant locally reacting materials

Response to "comment on 'reducing seat dip attenuation'" J. Acoust. Soc. Am. 110, 1260 (2001)

This letter responds to Klepper's comments [J. Acoust. Soc. Am. 110, 1260 (2001)] on the subject paper, which is concerned with ameliorating seat dip attenuation in auditoria by introducing a pit under the seats. Klepper asks what the effect of the pit will be on seat absorption and reverberation times. A little evidence is presented to support the idea that low-frequency absorption in an auditorium will increase with a pit. It is further speculated that reverberation times could be predicted by using a coupled space model. Klepper's suggestion of an experiment to answer his questions is supported. (C) 2001 Acoustical Society of America

Speech Transmission Index from running speech : a neural network approach

Speech Transmission Index (STI) is an important objective parameter concerning speech intelligibility for sound transmission channels. It is normally measured with specific test signals to ensure high accuracy and good repeatability. Measurement with running speech was previously proposed, but accuracy is compromised and hence applications limited. A new approach that uses artificial neural networks to accurately extract the STI from received running speech is developed in this paper. Neural networks are trained on a large set of transmitted speech examples with prior knowledge of the transmission channels' STIs. The networks perform complicated nonlinear function mappings and spectral feature memorization to enable accurate objective parameter extraction from transmitted speech. Validations via simulations demonstrate the feasibility of this new method on a one-net-one-speech extract basis. In this case, accuracy is comparable with normal measurement methods. This provides an alternative to standard measurement techniques, and it is intended that the neural network method can facilitate occupied room acoustic measurements