International Congress on Sound and Vibration (ICSV) London 2017

The International Congress on Sound and Vibration (ICSV) may not be the first conference you would think of for publishing the results of research into a sound effect but that’s exactly what we have just returned from. I presented our paper on the Real-Time Physical Model of an Aeolian harp to a worldwide audience of the top researchers in sound and vibration.

 

The Congress opened with a keynote from Professor Eric Heller discussing acoustics resonance and formants following by a whole day of musical acoustics chaired by Professor Murray Campbell from Edinburgh University. One interesting talk was given by Stephen Dance of London South Bank University where a hearing study of music students was carried out. Their results showed that the hearing of the music students improved over the 3 years of their course even though none of the students would wear ear protection while playing. The only degradation of hearing was experienced by oboe players. Possible reasons being the fast attack time of the instrument and the fact that the oboe players were stood directly in front of the brass players when playing as an orchestra.

 

The opening day also had a talk titled – Artificial neural network based model for the crispness impression of the potato chip sounds  by Ercan Altinsoy from Dresden University of Technology. This researched looked into the acoustical properties of food and the impression of freshness that was inferred from this.

 

I presented my research on the Real-time physical model of an aeolian harp, describing the sound synthesis of this unusual musical instrument. The synthesis model captures the interaction between the mechanical vibration properties of each string and the vortices being shed from the wind blowing around them.

 

The session ended with Application of sinusoidal curves to shape design of chord sound plate and experimental verification by Bor-Tsuen Wang Department of Mechanical Engineering, National Pingtung University of Science and Technology, Pingtung, Taiwan. This work reviews the design concept of chord sound plate (CSP) that is a uniform thickness plate with special curved shape designed by Bezier curve (B-curve) method. The CSP can generate the percussion sound with three tone frequencies that consist of the musical note frequencies of triad chord.

 

A presentation from Gaku Minorikawa, Hosei University, Department of Mechanical Engineering, Faculty of Science and Engineering, Tokyo, Japan, discussed his research into the reduction of noise from fans – highly relevant to audio engineers who want the quietest computers as possible for a studio. Prediction for noise reduction and characteristics of flow induced noise on axial cooling fan 

 

There was an interesting session on the noise experienced in open plan offices and how other noise sources are introduced to apply acoustic masking to certain areas. The presentation by Charles Edgington illustrated practical implementations of such masking and considerations that have to be made. Practical considerations and experiences with sound masking’s latest technology

 

The testing of a number of water features within an open plan office was presented in Audio-visual preferences of water features used in open-plan offices by Zanyar Abdalrahman from Heriot-Watt University, School of Energy, Geoscience, Infrastructure and Society, Edinburgh. Here a number of water feature contractions were examined.

 

The difficulty of understanding the speech of the participants in both rooms of a video conference  was researched by Charlotte Hauervig-Jørgensen from Technical University of Denmark. Subjective rating and objective evaluation of the acoustic and indoor climate conditions in video conferencing rooms. Moving away from office acoustics to house construction I saw a fascinating talk by Francesco D’Alessandro, University of Perugia. This paper aims at investigating the acoustic properties of straw bale constructions. Straw as an acoustic material

 

One session was dedicated to Sound Field Control and 3D Audio with a total of 18 papers presented on this topic. Filippo Fazi from University of Southampton presented a paper on A loudspeaker array for 2 people transaural reproduction which introduced a signal processing approach for performing 2-people Transaural reproduction using a combination of 2 single-listener cross-talk cancellation (CTC) beamformers, so that the CTC is maximised at one listener position and the beamformer side-lobes radiate little energy not to affect the other listening position.

 

Another session running was Thermoacoustics research in a gender-balanced setting. For this session alternate female and male speakers presented their work on thermoacoustics. Francesca Sogaro from Imperial College London presented her work on Sensitivity analysis of thermoacoustic instabilities. Presenting Sensescapes fascilitating life quality, Frans Mossberg of The Sound Environment Center at Lund University, Sweden is examine research into what can be done to raise awareness of the significance of sense- and soundscape for health, wellbeing and communication.

 

The hearing aid is a complex yet common device used to assist those suffering from hearing loss. In their paper on Speech quality enhancement in digital hearing aids: an active noise control approach, Somanath Pradhan, (Indian Institute of Technology Gandhinagar), has attempted to overcome limitations of noise reduction techniques by introducing a reduced complexity integrated active noise cancellation approach, along with noise reduction schemes.

 

Through a combination of acoustic computer modelling, network protocol, game design and signal processing, the paper Head-tracked auralisations for a dynamic audio experience in virtual reality sceneries proposes a method for bridging acoustic simulations and interactive technologies, i.e. fostering a dynamic acoustic experience for virtual scenes via VR-oriented auralisations. This was presented by Eric Ballesteros, London South Bank University.

 

The final day also included a number of additional presentations form our co-author, Dr Avital, including ‘Differences in the Non Linear Propagation of Crackle and Screech and Aerodynamic and Aeroacoustic Re-Design of Low Speed Blade Profile. The conference’s final night concluded with a banquet at the Sheraton Park Lane Hotel in its Grade 2 listed ballroom. The night included a string quartet, awards and Japanese opera singing. Overall this was a conference with a vast number of presentations from a number of different fields.
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Fourier in the ear

The cochlea is a coiled cavity within the inner ear that is primarily responsible for much of our auditory system. Within the cochlea is the basilar membrane, a filmy structure that divides the cochlea and vibrates with incoming sound energy. The width of the basilar increases from the base (entrance) to apex (end), while the width of the cochlear cavity decreases.

The basilar membrane has thousands of basilar fibers embedded within. These fibers affect the local stiffness in the membrane. The membrane starts thick and stiff, but becomes thinner and more flexible toward its apex. When sound waves travel along the basilar membrane, sound energy is dissipated at the place along the membrane which has the same natural resonant frequency. The stiff fibers will resonate with high frequencies, and the more flexible fibers resonate at lower frequencies.

The hair cells along the length of the basilar membrane detect this vibration and convert it into electrical potentials for transmission to the brain. There are also outer hair cells that contract in response to signals from the brain. This allows the brain to adjust or tune the stiffness of the membrane, thus providing a feedback mechanism to enhance the resolution of frequency content.

Together, the basilar membrane and hair cells give a continuum of natural resonance from high frequencies at the base to low frequencies at the apex. This distributes the energy over space as a function of frequency. (the distribution is logarithmic, which also accounts for why we hear sound on a log scale). Thus, the cochlea acts as a filterbank, performing a Fourier decomposition of the incoming sound.

Interestingly, this is a reversal of the normal frequency representation, since the highest frequencies appear at the entrance to the cochlea, and the lowest frequencies at the rear.