What the f*** are DFA faders?

I’ve been meaning to write this blog entry for a while, and I’ve finally gotten around to it. At the 142nd AES Convention, there were two papers that really stood out which weren’t discussed in our convention preview or convention wrap-up. One was about Acoustic Energy Harvesting, which we discussed a few weeks ago, and the other was titled ‘The DFA Fader: Exploring the Power of Suggestion in Loudness The DFA Fader: Exploring the Power of Suggestion in Loudness Judgments.’ When I mentioned this paper to others, their response was always the same, “What’s a DFA Fader?” . Well, the answer is hinted at in the title of this blog entry.

The basic idea is that musicians often give instructions to the sound engineer that he or she can’t or doesn’t want to follow. For instance, a vocalist might say “Turn me up” in a soundcheck, but the sound engineer knows that the vocals are at a nice level already and any more amplification might cause feedback. Sometimes, this sort of thing can be communicated back to the musician in a nice way. But there’s also the fallback option; a fader on the mixing console that “Does F*** All”, aka DFA. The engineer can slide the fader or twiddle an unconnected dial, smile back and say ‘Ok, does this sound a bit better?’.

A couple of companies have had fun with this idea. Funk Logic’s Palindrometer, shown below, is nothing more than a filler for empty rack space. Its an interface that looks like it might do something, but at best, it just flashes some LEDs when one toggles switches and turns the knobs.

pal_main

RANE have the PI 14 Pseudoacoustic Infector . Its worth checking out the full description, complete with product review and data sheets. I especially like the schematic, copied below.

pi14bd.png

And in 2014, our own Brecht De Man  released The Wire, a freely available VST and AudioUnit plug-in that emulates a gold-plated, balanced, 100% lossless audio connector.

TheWire

Anyway, the authors of this paper had the bright idea of doing legitimate subjective evaluation of DFA faders. They didn’t make jokes in the paper, not even to explain the DFA acronym. They took 22 participants and divided them into an 11 person control group and an 11 person test group. In the control group, each subject participated in twenty trials where two identical musical excerpts were presented and the subject had to rate the difference in loudness of vocals between the two excerpts. Only ten excerpts were used, so each pair was used in two trials. In the test group, a sound engineer was present and he made scripted suggestions that he was adjusting the levels in each trial. He could be seen, but participants couldn’t see his hands moving on the console.

Not surprisingly, most trials showed a statistically significant difference between test and control groups, confirming the effectiveness of verbal suggestions associated with the DFA fader. And the authors picked up on an interesting point; results were far more significant for stimuli where vocals were masked by other instruments. This links the work to psychoacoustic studies. Not only is our perception of loudness/timbre influenced by the presence of a masker, but we have a more difficult time judging loudness and hence are more likely to accept the suggestion from an expert.

The authors did an excellent job of critiquing their results. But unfortunately, the full data was not made available with the paper. So we are left with a lot of questions. What were these scripted suggestions? It could make a big difference if the engineer said “I’m going to turn the vocals way up” versus “Let me try something. Does it sound any different now?” And were some participants immune to the suggestions? And because participants couldn’t see a fader being adjusted (interviews with sound engineers had stressed the importance of verbal suggestions), we don’t know how that could influence results.

There is something else that’s very interesting about this. It’s a ‘false experiment’. The whole listening test is a trick since for all participants and in all trials, there was never any loudness differences between the two presented stimuli. So indirectly, it looks at an ‘auditory placebo effect’ that is more fundamental than DFA faders. What were the ratings for loudness differences that participants gave? For the control group especially, did they judge these differences to be small because they trusted their ears, or large because they knew that loudness judging is the nature of the test? Perhaps there is a natural uncertainty in loudness perception regardless of bias. How much weaker does a listener’s judgment become when repeatedly asked to make very subtle choices in a listening test? There’s been some prior work tackling some of these questions, but I think this DFA Faders paper opened up a lot of avenues of interesting research.

Female pioneers in audio engineering

The Heyser lecture is a distinguished talk given at each AES Convention by eminent individuals in audio engineering and related fields. At the 140th AES Convention, Rozenn Nicol was the Heyser lecturer. This was well-deserved, and she has made major contributions to the field of immersive audio. But what was shocking about this is that she is the first woman Heyser lecturer. Its an indicator that woman are under-represented and under-recognised in the field. With that in mind, I’d like to highlight some women who have made major contributions to the field, especially in research and innovation.

  • Birgitta Berglund led major research into the impact of noise on communities. Her influential research resulted in guidelines from the World Health Organisation, and greatly advanced our understanding of noise and its effects on society. She was the 2009 IOA Rayleigh medal recipient.
  • Marina Bosi is a past AES president of the AES. She has been instrumental in the development of standards for audio coding and digital content management standards and formats, including develop the AC-2, AC-3, and MPEG-2 Advanced Audio Coding technologies,
  • Anne-Marie Bruneau has been one of the most important researchers on electrodynamic loudspeaker design, exploring motion impedance and radiation patterns, as well as establishing some of the main analysis and measurement approaches used today. She co-founded the Laboratoire d’Acoustique de l’Université du Maine, now a leading acoustics research center.
  • Ilene J. Busch-Vishniac is responsible for major advances in the theory and understanding of electret microphones, as well as patenting several new designs. She received the ASA R. Bruce Lindsay Award in 1987, and the Silver Medal in Engineering Acoustics in 2001. President of the ASA 2003-4.
  • betzcohen-headshot_med_hrElizabeth (Betsy) Cohen was the first female president of the Audio Engineering Society. She was presented with the AES Fellowship Award in 1995 for contributions to understanding the acoustics and psychoacoustics of sound in rooms. In 2001, she was presented with the AES Citation Award for pioneering the technology enabling collaborative multichannel performance over the broadband internet.
  • crumPoppy Crum is head scientist at Dolby Laboratories whose research involves computer research in music and acoustics. At Dolby, she is responsible for integrating neuroscience and knowledge of sensory perception into algorithm design, technological development, and technology strategy.
  • Delia Derbyshire (1937-2001) was an innovator in electronic music who pushed the boundaries of technology and composition. She is most well-known for her electronic arrangement of the theme for Doctor Who, an important example of Musique Concrète. Each note was individually crafted by cutting, splicing, and stretching or compressing segments of analogue tape which contained recordings of a plucked string, oscillators and white noise. Here’s a video detailing a lot of the effects she used, which have now become popular tools in digital music production.
  •  Ann Dowling is the first female president of the Royal Academy of Engineering. Her research focuses on noise analysis and reduction, especially from engines, and she is a leading educator in acoustics. A quick glance at google scholar shows how influential her research has been.
  • Marion Downs was an audiometrist at Colorado Medical Center in Denver, who invented the tests used to measure hearing both In newly born babies and in fetuses.
  • Judy Dubno is Director of Hearing Research at the Medical University of South Carolina. Her research focuses on human auditory function, with emphasis on the processing of auditory information and the recognition of speech, and how these abilities change in adverse listening conditions, with age, and with hearing loss. Recipient of the James Jerger Career Award for Research in Audiology from the American Academy of Audiology and Carhart Memorial Lecturer for the American Auditory Society. President of the ASA in 2014-15.
  • thumb_FiebrinkPhoto3Rebecca Fiebrink researches Human Computer Interaction (HCI) and its application of machine learning to real-time, interactive, and creative domains. She is the creator of the popular Wekinator, which allows anyone to use machine learning to build new musical instruments, real-time music information retrieval and audio analysis systems, computer listening systems and more.
  • Katherine Safford Harris pioneered EMG studies of speech production and auditory perception. Her research was fundamental to speech recognition, speech synthesis, reading machines for the blind, and the motor theory of speech perception. She was elected Fellow of the ASA, the AAAS, the American Speech-Language-Hearing Association, and the New York Academy of Sciences. She was President of the ASA (2000-2001), awarded the Silver Medal in 2005 and Gold Medal in 2007.
  • Rhona Hellman was a Fellow of the ASA. She was a distinguished hearing scientist and preeminent expert in auditory perceptual phenomena. Her research spanned almost 50 years, beginning in 1960. She tackled almost every aspect of loudness, and the work resulted in major advances and developments of loudness standards.
  • Mara Helmuth developed software for composition and improvisation involving granular synthesis. Throughout the 1990s, she paved the way forward by exploring and implementing systems for collaborative performance over the Internet. From 2008-10 she was President of the International Computer Music Association.
  • Carleen_HutchinsCarlene Hutchins (1911-2009) was a leading researcher in the study of violin acoustics, with over a hundred publications in the field. She was founder and president of the Catgut Society, an organization devoted to the study and appreciation of stringed instruments .
  • Sophie Germain (1776-1831) was a French mathematician, scientist and philosopher. She won a major prize from the French Academy of Sciences for developing a theory to explain the vibration of plates due to sound. The history behind her contribution, and the reactions of leading French mathematicians to having a female of similar calibre in their midst, is fascinating. Joseph Fourier, whose work underpins much of audio signal processing, was a champion of her work.
  • Bronwyn Jones was a psychoacoustician at the CBS Technology Center during the 70s and 80s. In seminal work with co-author Emil Torrick, she developed one of the first loudness meters, incorporating both psychoacoustic principles and detailed listening tests. It paved the way for what became major initiatives for loudness measurement, and in some ways outperforms the modern ITU 1770 standard
  • Bozena Kostek is editor of the Journal of the Audio Engineering Society. Her most significant contributions include the applications of neural networks, fuzzy logic and rough sets to musical acoustics, and the application of data processing and information retrieval to the psychophysiology of hearing. Her research has garnered dozens of prizes and awards.
  • Daphne Oram (1925 –2003) was a pioneer of ‘musique concrete’ and a central figure in the evolution of electronic music. She devised the Oramics technique for creating electronic sounds, co-founded the BBC Radiophonic Workshop, and was possibly the first woman to direct an electronic music studio, to set up a personal electronic music studio and to design and construct an electronic musical instrument.
  • scalettiCarla Scaletti is an innovator in computer generated music. She designed the Kyma sound generation computer language in 1986 and co-founded Symbolic Sound Corporation in 1989. Kyma is one of the first graphical programming languages for real time digital audio signal processing, a precursor to MaxMSP and PureData, and is still popular today.
  • Bridget Shield was professor of acoustics at London Southbank University. Her research is most significant in our understanding of the effects of noise on children, and has influenced many government initiatives. From 2012-14, she was the first female President of the Institute of Acoustics.
  • Laurie Spiegel created one of the first computer-based music composition programs, Music Mouse: an Intelligent Instrument, which also has some early examples of algorithmic composition and intelligent automation, both of which are hot research topics today.
  • maryMary Desiree Waller (1886-1959) wrote a definitive treatise on Chladni figures, which are the shapes and patterns made by surface vibrations due to sound, see Sophie Germain, above. It gave far deeper insight into the figures than any previous work.
  • Megan (or Margaret) Watts-Hughes is the inventor of the Eidophone, an early instrument for visualising the sounds made by your voice. She rediscovered this simple method of generating Chladni figures without knowledge of Sophie Germain or Ernst Chladni’s work. There is a great description of her experiments and analysis in her own words.

The Eidophone, demonstrated by Grace Digney.

Do you know some others who should be mentioned? We’d love to hear your thoughts.

Thanks to Theresa Leonard for information on past AES presidents. She was the third female president. Will there be a fourth one soon?

Behind the spectacular sound of ‘Dunkirk’ – with Richard King: — A Sound Effect

The post Behind the spectacular sound of ‘Dunkirk’ – with Richard King: appeared first on A Sound Effect. Its an interesting interview giving deep insights into sound design and soundscape creation for film. It caught my attention first because of the mention of Richard King. But its not Richard King, Grammy award winning professor in sound recording at University of McGill. Its the other one, the Oscar award winning supervising sound editor at Warner Brothers Sound.

We collaborated with Prof. Richard King on a couple of papers. In [1], we conducted an experiment where eight songs were each mixed by eight different engineers. We analysed audio features from the multitracks and mixes. This allowed us to test various assumed rules of mixing practice. In the follow-up [2], the mixes were all rated by experienced test subjects. We used the ratings to investigate relationships between perceived mix quality and sonic features of the mixes.

[1] B. De Man, M. Boerum, B. Leonard, R. King, G. Massenburg and J. D. Reiss, ‘Perceptual Evaluation of Music Mixing Practices,’ 138th Audio Engineering Society (AES) Convention, May 2015

[2] B. De Man, B. Leonard, R. King and Joshua D. Reiss, “An analysis and evaluation of audio features for multitrack music mixtures,” 15th Int. Society for Music Information Retrieval Conference (ISMIR-14), Taipei, Taiwan, Oct. 2014

via Behind the spectacular sound of ‘Dunkirk’ – with Richard King: — A Sound Effect

Joshua D Reiss – Professor of Audio Engineering

Intelligent Sound Engineering are pleased to announce our lead academic, Joshua D Reiss has been promoted to Professor of Audio Engineering.

Professor Reiss holds degrees in Physics and Mathematics, and a PhD in Chaos Theory from Georgia Institute of Technology. He has been an academic with the Centre for Digital Music in the Electronic Engineering and Computer Science department at Queen Mary University of London since 2003. His primary focus of research is on state-of-the-art signal processing techniques for sound engineering, publishing over 160 scientific papers and authoring the book “Audio Effects: Theory, Implementation and Application” together with Andrew McPherson. Along with pioneering research into intelligent audio production technologies, Professor Reiss also focuses on state of the art sound synthesis techniques.

Professor Reiss is a visiting Professor at Birmingham City University, an Enterprise Fellow of the Royal Academy of Engineering and has been a governor of the Audio Engineering Society from 2013 to present.

So you want to write a research paper

The Audio Engineering research team here submit a lot of conference papers. In our internal reviewing and when we review submissions by others, certain things come up again and again. I’ve compiled all this together as some general advice for putting together a research paper for an academic conference, especially in engineering or computer science. Of course, there are always exceptions, and the advice below doesn’t always apply. But its worth thinking of this as a checklist to catch errors and issues in an early draft.

researchpaper
Abstract
Make sure the abstract is self-contained. Don’t assume the person reading the abstract will read the paper, or vice-versa. Avoid acronyms. Be sure to actually say what the results were and what you found out, rather than just saying you applied the techniques and analysed the data that came out.
The abstract is part summary of the paper, and part an advertisement for why someone should read the paper. And keep in mind that far more people read the abstract than read the paper itself.
Introduction
Make clear what the problem is and why it is important. Why is this paper needed, and what is going to distinguish this paper from the others?
In the last paragraph, outline the structure of the rest of the paper. But make sure that it is specific to the structure of the paper.

Background/state of the art/prior work – this could be a subsection of introduction, text within the introduction, or its own section right after the introduction. What have others done, what is the most closely related work? Don’t just list a lot of references. Have something to say about each reference, and relate them to the paper. If a lot of people have approached the same or similar problems, consider putting the methods into a table, where for each method, you have columns for short description, the reference(s), their various properties and their assumptions. If you think no one has dealt with your topic before, you probably just haven’t looked deep enough 😉 . Regardless, you should still explain what is the closest work, perhaps highlighting how they’ve overlooked your specific problem.

Problem formulation – after describing state of the art, this could be a subsection of introduction, text within the introduction, or its own section. Give a clear and unambiguous statement of the problem, as you define it and as it is addressed herein. The aim here is to be rigorous, and remove any doubt about what you are doing. It also allows other work to be framed in the same way. When appropriate, this is described mathematically, e.g., we define these terms, assume this and that, and we attempt to find an optimal solution to the following equation.

Method/Analysis/Results
The structure of this, the core of the paper, is highly dependent on the specific work. One good approach is to have quite a lot of figures and tables. Then most of the writing is mainly just explaining and discusses these figures and tables, and the ordering of these should be mostly clear.
A typical ordering is
Describe the method, giving block diagrams where appropriate
Give any plots that analyse and illustrate the method, but aren’t using the method to produce results that address the problem
Present the results of using your method to address the problem. Keep the interpretation of the results here short, unless detailed explanation of a result it is needed to justify the next result that is presented. If there is lengthy discussion or interpretation, then leave that to a discussion section.

Equations and notation
For most papers in signal processing and related fields, at least a few equations are expected. The aim with equations is always to make the paper more understandable and less ambiguous. So avoid including equations just for the sake of it, avoid equations if they are just an obvious intermediate step, or if they aren’t really used in any way (e.g. ‘we use the Fourier transform, which by the way, can be given in this equation. Moving on…’), do use equations if they clear up any confusion when a technical concept is explained just with text.
Make sure every equation can be fully understood. All terms and notation should be defined, right before or right after they are used in the text. The logic or process of going from one equation to the next should be made clear.
Tables and figures
Where possible, these should be somewhat self-contained. So one should be able to look at a figure and understand it without reading the paper. If that isn’t possible, then it should be understood just by looking at the figure and figure caption. If not, then by just looking at the figure, caption and a small amount of text where the figure is described.
Figure captions typically go immediately below figures, but table captions typically above tables.
Label axes in figures wherever possible, and give units. If units are not appropriate, make clear that an axis is unitless. For any text within a figure, make sure that the font size used is close to the font size of the main text in the paper. Often, if you import a figure from software intending for viewing on a screen (like matlab), then the font can appear miniscule when the figure is imported into a paper.
Make sure all figures and tables are numbered and are all referenced, by their number, in the main text. Position them close to where they are first mentioned in the text. Don’t use phrasing that refers to their location, like ‘the figure below’ or ‘the table on the next page’, partly because their location may change in the final version.
Make sure all figures are high quality. Print out the paper before submitting and check that it all looks good, is high resolution, and nicely formatted.

researchpaperconclusion

Discussion/Future work/conclusion
Discussion and future work may be separate sections or part of the conclusion. Discussion is useful if the results need to be interpreted, but is often kept very brief in short papers where the results may speak for themselves.
Future work is not about what the author plans to do next. Its about research questions that arose or were not addressed, and research directions that are worth pursuing. The answers to these research questions may be pursued by the author or others. Here, you are encouraging others to build on the work in this paper, and suggesting to them the most promising directions and approaches. Future work is usually just a couple sentences or couple paragraphs at the end of conclusion, unless there is something particularly special about it.
The conclusion should not simply repeat the abstract or summarise the paper, though there may be an element of that. Its about getting across what were the main things that the reader should take away and remember. What was found out? What was surprising? What are the main insights that arose? If the research question is straightforward and directly addressed, what was the answer?

researchpaperbib

References
The most important criterion for references is to cite wherever it justifies a claim, clarifies a point, identifies where an idea is coming from someone else, or helps the reader find pertinent additional material. If you’re dealing with a very niche or underexplored topic, you may wish to give a full review of all existing literature on the subject.
Aim for references to come from high impact, recent peer reviewed journal articles, or as close to that as possible. So for instance, choose a journal over a conference article if you can, but maybe a highly cited conference paper over an obscure journal paper.
Avoid using web site references. If the reference is essentially just a URL, then put that directly in the text or as a footnote, but not as a citation. And no one cares when you accessed the website so no need to say ‘accessed on [date]’. If it’s a temporary record that may have only been there for a short period of time before the paper submission date, its probably not a reliable reference, won’t help the reader and you should probably find an alternative citation.
Check your reference formatting, especially if you use someone else’s reference library or some automatically generated citations. For instance some citations will have a publisher and a conference name, so it reads as ‘the X Society Conference, published by the X Society.
Be consistent. So for instance, have all references use author initials, or none of them. Always use journal abbreviations, or never use them. Always include the city of a conference, or never do it. And so on.

The future of headphones

headphonememe

Headphones have been around for over a hundred years, but recently there has been a surge in new technologies, spurred on in part by the explosive popularity of Beats headphones. In this blog, we will look at three advances in headphones arising from high tech start-ups. I’ve been introduced to each of these companies recently, but don’t have any affiliation with them.

EAVE (formerly Eartex) are a London-based company, who have developed headphones aimed at the industrial workplace; construction sites, the maritime industry… Typical ear defenders do a good job of blocking out noise, but make communication extremely difficult. EAVE’s headphones are designed to protect from excessive noise, yet still allow effective communication with others. One of the founders, David Greenberg, has a background in auditory neuroscience, focusing on hearing disorders. He brought that knowledge to the company. He used his knowledge of hearing aids to design headphones that amplify speech while attenuating noise sources. They are designed for use in existing communication networks, and use beam forming microphones to focus the microphone on the speaker’s voice. They also have sensors to monitor noise levels so that noise maps can be created and personal noise exposure data can be gathered.

This use of additional sensors in the headset opens up lots of opportunities. Ossic are a company that emerged from Abbey Road Red, the start-up incubator established by the legendary Abbey Road Studios. Their headphone is packed with sensors, measuring the shape of your ears, head and torso. This allows them to estimate your own head-related transfer function, or HRTF, which describes how sounds are filtered as they travel from to your ear canal. They can then apply this filtering to the headphone output, allowing sounds to be far more accurately placed around you. Without HRTF filtering, sources always appear to be coming from inside your head.

Its not as simple as that of course. For instance, when you move your head, you can still identify the direction of arrival of different sound sources. So the Ossic headphones also incorporate head tracking. And a well-measured HRTF is essential for accurate localization, but calibration to the ear is not perfect. So their headphones also have eight drivers rather than the usual two, allowing more careful positioning of sounds over a wide range of frequencies.

Ossic was funded by a Kickstarter campaign. Another headphone start-up, Ora, currently has a Kickstarter campaign. Ora is a venture that was founded at Tandem Launch, who create companies often arising from academic research, and have previously invested in research arising from the audio engineering research team behind this blog.

Ora aim to release ‘the world’s first graphene headphones.’ Graphene is a form of carbon, shaped in a one atom thick lattice of hexagons. In 2004, Andre Geim and Konstantin Novoselov of the University of Manchester, isolated the material, analysed its properties, and showed how it could be easily fabricated, for which they won the Nobel prize in 2010. Andre Geim, by the way, is a colourful character, and the only person to have won both the Nobel and Ig Nobel prizes, the latter awarded for experiments involving levitating frogs.

graphene-headGraphene

Graphene has some amazing properties. Its 200 times stronger than the strongest steel, efficiently conducts heat and electricity and is nearly transparent. In 2013, Zhou and Zettl published early results on a graphene-based loudspeaker. In 2014, Dejan Todorovic and colleagues investigated the feasibility of graphene as a microphone membrane, and simulations suggested that it could have high sensitivity (the voltage generated in response to a pressure input) over a wide frequency range, far better than conventional microphones. Later that year, Peter Gaskell and others from McGill University performed physical and acoustical measurements of graphene oxide which confirmed Todorovic’s simulation results. Interestingly, they seemed unaware of Todorovic’s work.

graphene_speaker_640Graphene loudspeaker, courtesy Zettl Research Group, Lawrence Berkeley National Laboratory and University of California at Berkeley

Ora’s founders include some of the graphene microphone researchers from McGill University. Ora’s headphone uses a Graphene-based composite material optimized for use in acoustic transducers. One of the many benefits is the very wide frequency range, making it an appealing choice for high resolution audio reproduction.

I should be clear. This blog is not meant as an endorsement of any of the mentioned companies. I haven’t tried their products. They are a sample of what is going on at the frontiers of headphone technology, but by no means cover the full range of exciting developments. Still, one thing is clear. High-end headphones in the near future will sound very different from the typical consumer headphones around today.

Acoustic Energy Harvesting

At the recent Audio Engineering Society Convention, one of the most interesting talks was in the E-Briefs sessions. These are usually short presentations, dealing with late-breaking research results, work in progress, or engineering reports. The work, by Charalampos Papadokos presented an e-brief titled ‘Power Out of Thin Air: Harvesting of Acoustic Energy’.

Ambient energy sources are those sources all around us, like solar and kinetic energy. Energy harvesting is the capture and storage of ambient energy. It’s not a new concept at all, and dates back to the windmill and the waterwheel. Ambient power has been collected from electromagnetic radiation since the invention of crystal radios by Sir Jagadish Chandra Bose, a true renaissance man who made important contributions to many fields. But nowadays, people are looking for energy harvesting from many more possible sources, often for powering small devices, like wearable electronics and wireless sensor networks. The big advantages, of course, is that energy harvesters do not consume resources like oil or coal, and energy harvesting might enable some devices to operate almost indefinitely.

But two of the main challenges is that many ambient energy sources are very low power, and the harvesting may be difficult.

Typical power densities from energy harvesting can vary over orders of magnitude. Here’s the energy densities for various ambient sources, taken from the Open Access book chapter ‘Electrostatic Conversion for Vibration Energy Harvesting‘ by S. Boisseau, G. Despesse and B. Ahmed Seddik ‘.

EnergyHarvesting

You can see that vibration, which includes acoustic vibrations, has about 1/100th the energy density of solar power, or even less. The numbers are arguable, but at first glance it looks like it will be exceedingly difficult to get any significant energy from acoustic sources unless one can harvest over a very large area.

That’s where this e-brief paper comes in. Papadokos and his co-author, John Mourjopoulos, have a patented approach to harvesting the acoustic energy inside a loudspeaker enclosure. Others had considered harvesting the sound energy from loudspeakers before (see the work of Matsuda, for instance), but mainly just as a way of testing their harvesting approach, and not really exploiting the properties of loudspeakers. Papadokos and Mourjopoulos had the insight to realise that many loudspeakers are enclosed and the enclosure has abundant acoustic energy that might be harvested without interfering with the external design and without interfering with the sound presented to the listener. In earlier work, Papadokos and Mourjopoulos found that sound pressure within the enclosure often exceeds 130 dBs within a loudspeaker enclosure. Here, they simulated the effect of a piezoelectric plate in the enclosure, to convert the acoustic energy to electrical energy. Results showed that it might be possible to generate 2.6 volts under regular operating conditions, thus proving the concept of harvesting acoustic energy from loudspeaker enclosures, at least in simulation.