"Set phasors to stun": an algorithm to improve phase coherence on transients in multi-microphone recordings

Ever since the advent of multi-microphone recording, sound engineers have wrestled with the colouration of sound by phasing issues. For some this was an anathema; for others this colouration was a crucial ingredient of the finished product. Traditionally, delicate microphone placement was essential, with subtle movements and tilts allowing the producer/engineer to determine when a sound was “in phase” based on perception alone. More recently, DAW’s have allowed us to view multiple waveforms and manually nudge them into coherence with visual feedback now supporting the aural, although still a manual process. This paper will present an algorithm that allows automatic correction of phase via a unique Max/MSP patch operating on multiple audio components simultaneously. With a single button push, the producer can now hear a stereo recording with maximum coherence and thus make an artistic judgment as to whether the “ideal” is ideal, or better to pursue naturally occurring phase colouration in preference. In addition, the patch allows zoning in to spatially separated sound sources, eg tuning drum kit overheads to phase lock with the snare drum or hi-hat microphone. Audio examples will be played and the patch demonstrated in action. Limiting factors, contexts and applications will also be discussed

Cutting tracks, making CDs: a comparative study of audio time-correction techniques in the desktop age.

Producers have long sought to “tighten” studio performances. Software-based DAW’s now come with proprietary functions to facilitate this, but only the latest generation of platforms allow relative ease of use on longer takes. Each method has advantages and disadvantages in terms of ease and speed of use, transient preservation, implied subsequent workflow and (usually) unwanted artifacts. Whilst rhythmically consistent material with clear transients is readily controllable with contemporary tools, working with complex mixtures of note-values still presents a challenge and requires much user intervention. This paper performs a comparative study of different audio quantize techniques on percussive material, often on rhythmically complex performances. It will seek to compare necessary methodologies and workflow implications through the use of several contemporary systems: Recycle, Pro Tools, Logic, Cubase, Live, Melodyne, and Nuendo. The current level of man-machine interaction will be explored, and the best features from each platform will be collated. A model for the future will be speculatively presented

"Killing spillage": an algorithm to reduce microphone spillage and improve phase coherence.

Since the earliest days of multi-microphone live recording, the problem of spillage has dogged the sound engineer. Numerous strategies have evolved including microphone placement, acoustic screening, gating and phase inversion. The acoustic content of spillage can vary from a near direct signal in the case of adjacent mics on a drum kit to almost pure reverb in the case of a live recording with acoustically significant spacing between the performers. In certain physical setups, the problem is unavoidable and inevitably compromises the degree of control that can be exercised when mixing. It is principally for this reason that it is considered ‘a problem’. If spillage could be tamed, then the impact on all production would indeed be profound. Classical recordings might afford the producer radical new “Rock’n’Roll” interventionist techniques. Rock producers might be tempted to allow bands to play live in a room even when a highly “separated’ sound is the ultimate goal, and jazz musicians might avoid having to wear the headphones they so often dread. That is only the beginning. This paper will present a radical new working methodology that can dramatically reduce spillage in a way never before possible by utilising convolution technology that could be coupled with almost any “traditional” recording technique, but will focus on time-delayed and ambient problems. A unique Max/MSP patch will be demonstrated and audio examples will be played to illustrate the effectiveness of the approach. It will delve into commonly understood theory yet demonstrate for the first time, one of tomorrow’s “traditional” recording techniques

The effect of dynamic range compression on the psychoacoustic quality and loudness of commercial music

It is common practice for music productions to be mastered with the aim of increasing the perceived loudness for the listener, allowing one record to stand out from another by delivering an immediate impact and intensity. Since the advent of the Compact Disc in 1980, music has increased in RMS level by up to 20dB. This results in many commercial releases being compressed to a dynamic range of 2–3 dB. Initial findings of this study have determined that amplitude compression adversely affects the audio signal with the introduction of audible artifacts such as sudden gain changes, modulation of the noise floor and signal distortion, all of which appear to be related to the onset of listener fatigue. In this paper, the history and changes in trends with respect to dynamic range are discussed and findings will be presented and evaluated. Initial experimentation, and both the roadmap and challenges for further and wider research are also described and discussed. The key aim of this research is to quantify the effects (both positive and negative) of dynamic range manipulation on the audio signal and subsequent listener experience. A future goal of this study is to ultimately define recommended standards for the dynamic range levels of mastered music in a similar manner to those associated with the film industry

A study, exploration and development of the interaction of music production techniques in a contemporary desktop setting

As with all computer-based technologies, music production is advancing at a rate comparable to ‘Moore’s law’. Developments within the discipline are gathering momentum exponentially; stretching the boundaries of the field, deepening the levels to which mediation can be applied, concatenating previously discrete hardware technologies into the desktop domain, demanding greater insight from practitioners to master these technologies and even defining new genres of music through the increasing potential for sonic creativity to evolve. This DMus project will draw from the implications of the above developments and study the application of technologies currently available in the desktop environment, from emulations of that which was traditionally hardware to the latest spectrally based audio-manipulation tools. It will investigate the interaction of these technologies, and explore creative possibilities that were unattainable only a few years ago – all as exemplified through the production of two contrasting albums of music. In addition, new software will be developed to actively contribute to the evolution of music production as we know it. The focus will be on extended production technique and innovation, through both development and context. The commentary will frame the practical work. It will offer a research context with a number of foci in preference to literal questions, it will qualify the methodology and then form a literature & practice review. It will then present a series of frameworks that analyse music production contexts and technologies in a historical perspective. By setting such a trajectory, the current state-of-the-art can be best placed, and a number of the progressive production techniques associated with the submitted artefacts can then by contextualised. It will terminate with a discussion of the work that moves from the specific to the general

Producing 3-D audio

Arguably the most rapidly expanding market for audio production is that of 3-D audio – 360° spatial audio with representation of height. Such playback is becoming commonplace in cinemas, and multi-speaker home setups are following. As these mature, greater convenience and enhanced functionality will likely increase domestic uptake. In parallel, headphone-based 3D is experiencing an unprecedented rate of development. Headphones with spaced multiple drivers are emerging, accelerometers are being incorporated to facilitate head-tracking-driven audio panning, and binaural algorithms are steadily improving. The principal exponents of such playback are virtual and augmented reality. While gaming will lead this market, soon the applications will proliferate into many areas of daily life – from productivity to education, through social networking to music playback, and advertising will pervade these new media. All of these applications require the production of audio, and this chapter explores the associated implications for the music producer. 3D offers an exciting new paradigm for music, since the conventions associated with stereo and horizontal surround are increasingly outmoded by the greater options associated with perception of height. This chapter will consider relevant technologies and identify key production-practice, underpinned by a framework of scientific research to help define the emergent praxis of 3-D audio production. It will consider opportunities, applications and limitations, all of which combine to introduce and help define a new approach to music production that will increasingly pervade into the future

Immersive audio post-production for 360° video: workflow case studies

Perhaps the most pervasive immersive format at present is 360° video, which can be panned whilst being viewed. Typically, such footage is captured with a specialist camera. Approaches and workflow for the creation of 3-D audio for this medium are seldom documented, and methods are often heuristic. This paper offers insight into such approaches, and whilst centered on post-production, also discusses some aspects of audio capture. This is done via a number of case studies that draw from the commercial work of immersive-audio company, 1.618 Digital. Although these case studies are unified by certain common approaches, they also include unusual aspects such as binaural recording of insects, sonic capture of moving vehicles and the use of drones

Comorbidities, exposure to medications, and the risk of community-acquired clostridium difficile infection: a systematic review and meta-analysis

Background. Clostridium difficile infection (CDI) has been extensively escribedin healthcare settings; however, risk factor sassociated with community-acquired (CA) CDI remain uncertain. This study aimed to synthesize the current evidence for an association between commonly prescribed medications and comorbidities with CA-CDI. methods. A systematic search was conducted in 5 electronic databases for epidemiologicstudi esthatexamined the associtation between the presence of comorbidities and exposure to medications with the risk of CA-CDI. Pooled odds ratios were estimated using 3 meta-analytic methods. Subgroup analyses by location of studies and by life stages were conducted. results. Twelve publications (n=56,776 patients) met inclusion criteria. Antimicrobial (odds ratio, 6.18; 95% CI, 3.80-10.04) and corticosteroid (1.81; 1.15-2.84) exposure were associated with increased risk of CA-CDI. Among the comorbidities, inflammatory bowel disease (odds ratio, 3.72; 95% CI, 1.52-9.12), renal failure (2.64; 1.23-5.68), hematologic cancer (1.75; 1.02-5.68), and diabetes mellitus (1.15; 1.05-1.27) were associated with CA-CDI. By location, antimicrobial exposure was associated with a higher risk of CA-CDI in the United States, whereas proton-pump inhibitor exposure was associated with a higher risk in Europe. By life stages, the risk of CA-CDI associated with antimicrobial exposure greatly increased in adults older than 65 years. conclusions. Antimicrobial exposure was the strongest risk factor associated with CA-CDI. Further studies are required to investigate the risk of CA-CDI associated with medications commonly prescribed in the community. Patients with diarrhea who have inflammatory bowel disease, renal failure, hematologic cancer, or diabetes are appropriate populations for interventional studies of screening

Equation of state and coarse grained free energy for matrix models

We investigate phase transitions in three dimensional scalar matrix models, with special emphasis on complex $2 \times 2$ matrices. The universal equation of state for weak first order phase transitions is computed. We also study the coarse grained free energy. Its dependence on the coarse graining scale gives a quantitative criterion for the validity of the standard treatment of bubble nucleation.Comment: Latex, 48 page