Case Studies in the Absorption of Low Frequency Sound in Music Rooms

Room design for music is a special and highly valued skill. The spectrum, timbre and dynamics of music, coupled with our keen sense for musical sounds make these rooms a particular challenge for the acoustician. The goal is to create an acoustic environment whereby the sound field within the space supports the instruments and enhances their tone, with unfavourable colourations and effects minimised. Room dimensions, construction materials and specialised treatments must be chosen carefully to achieve the perfect musical balance for the performance. Architectural Acoustics is the field which brings together art and science to address the challenge of creating an environment suitable for music. The most challenging aspect is to achieve the required spectral balance, particularly at low frequency. This thesis presents a literature review of current knowledge of architectural acoustics for music and traditional acoustics treatments. This is followed by three case studies which each investigate a novel solution to improve the acoustic environment for musicians. The first case study investigated room boundaries as potential absorbers. The study arose at a music college who wanted an evaluation of a beautiful new recital hall. Professional musicians had expressed concern about the unusual acoustic in the hall. A room acoustic assessment is described, and results analysed and compared to standards and guidance. Multiple studies including modal analysis, physical experiments and wave-based computer simulation were undertaken to investigate the mechanism for the low frequency dip in the room response. It was determined that the false walls in the hall were acting as quarter wavelength resonators but for multiple low frequencies thus creating an effective absorber. This absorber design could be repurposed to reduce the boom commonly found in modern music venues. The second case study explored pneumatic absorbers. This investigation arose when a London orchestral rehearsal space wanted an inexpensive, quick to deploy, flexible acoustic which would reduce the low frequency boom in the space thereby balancing the room response. A variety of airbeds were selected for the study and tested in the laboratory with different levels of inflation. Finally, the position and number of the airbeds was investigated for optimisation purposes. The airbeds were installed in Henry Wood Hall and the room response measured. It was found the room response was flattened thus improving the acoustic quality. Conductors from world leading orchestras responded positively to the new condition of the hall. The third case study focused on the Targeted Energy Transfer method as a means of creating a novel low frequency absorber. This approach transferred knowledge from the field of vibration control to architectural acoustics. A test rig was built to measure the vibrational damping in two types of hyperelastic latex materials using a laser vibrometer. A small low frequency non-linear response was found but there was not enough evidence to pursue the research further

Day for Night: Facilitating Collaborative Solutions in the Pursuit of Approval for Human Subjects Research

For first-time researchers, the prospect of executing a Master’s thesis can be as exciting as it is daunting. Students pursuing skill sets in the helping professions may view their thesis not just as a way to contribute to their field of study and do something that will be helpful to society, but also as a way of contributing to treatment agencies that allow fledgling researchers access to human subjects. Unfortunately, good intentions, energy, and a positive outlook may not be enough to bring an idea for research to fruition. One need only begin the process of seeking Institutional Review Board (IRB) approval for the use of human subjects and other necessary approvals to uncover the dizzying necessity for coordination among many parties that must be in place for a study of any complexity to be executed. Just as a clock seems simple at a glance but reveals, upon further scrutiny, an engineer’s masterful efforts at integrating many moving parts and principles, so does the thesis study seem a natural and simple thing before the apprentice researcher uncovers the many principles and moving parts that must collaborate and work together harmoniously to create the illusion of effortlessness. Though difficult to navigate at times, the IRB process is absolutely necessary as evidenced by studies that predated the IRB and were infamously harmful to participants such as the Stanford Prison Experiment (SPE) and the Tuskegee Syphilis Experiment. This paper discusses the lessons learned by two student researchers in their efforts at such collaboration. It is written in hopes of identifying the unanticipated barriers that might keep other students from hearing that satisfying and deceptively simple ticking as they aspire to make a contribution of their own

Earthquake recurrence as a record breaking process

Extending the central concept of recurrence times for a point process to recurrent events in space-time allows us to characterize seismicity as a record breaking process using only spatiotemporal relations among events. Linking record breaking events with edges between nodes in a graph generates a complex dynamical network isolated from any length, time or magnitude scales set by the observer. For Southern California, the network of recurrences reveals new statistical features of seismicity with robust scaling laws. The rupture length and its scaling with magnitude emerges as a generic measure for distance between recurrent events. Further, the relative separations for subsequent records in space (or time) form a hierarchy with unexpected scaling properties

Pharmacokinetics and efficacy of oral versus intravenous mixed-micellar phylloquinone (vitamin K-1) in severe acute liver disease

Background/Aims: In patients with severe acute liver dysfunction, i.v. phylloquinone (vitamin K-1) may be given to exclude vitamin K deficiency, rather than impaired hepatic synthesis of coagulation factors alone, as the cause of the coagulopathy. However, there have been no studies of the pharmacokinetics or efficacy of i.v. or oral K-1 in such patients.Methods: 49 adults with severe acute liver disease were randomised double-blind to a single 10 mg dose of i.v. or oral mixed-micellar K-1, or placebo. Serum levels of phylloquinone and undercarboxylated prothrombin (PIVKA-II) were assessed before and after treatment.Results: At admission, 13 patients (27 %) had either low serum K-1 levels or elevated PIVKA-II concentrations, indicative of subclinical vitamin K deficiency. In the 16 patients who received i.v. K-1, there was one (6 %) treatment failure (K-1 rise < 10 ng/ml above baseline), compared with 12 of the 15 (80 %) who received oral K, (P < 0.0001). One patient in the placebo group developed overt vitamin K deficiency.Conclusions: A minority of patients with severe acute liver dysfunction have subclinical vitamin K deficiency at the time of presentation, which is corrected by a single dose of i.v. K-1. The intestinal absorption of mixed-micellar K, is unreliable in adults with severe acute liver dysfunction. (c) 2004 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved

The relationship between imagery type and collective efficacy in elite and non elite athletes

This study investigated the relationship between imagery function and individual perceptions of collective efficacy as a function of skill level. Elite (n = 70) and non elite (n = 71) athletes from a number of interactive team sports completed the Sport Imagery Questionnaire (SIQ) and the Collective Efficacy Inventory (CEI). Multiple hierarchical regression analysis was then used to examine which SIQ sub-scales predicted individual perceptions of collective efficacy. For the elite sample, Motivational General-Mastery (MG-M) imagery accounted for approximately 17% of the variance in collective efficacy scores. No significant predictions were observed in the non elite sample. The findings suggest MG-M imagery as a potential technique to improve levels of collective efficacy although competitive level may moderate the effectiveness of such intervention

Acoustic conditions in orchestra pits: are metadiffusers a potential solution?

Rising concerns about public health and safety have progressively induced a change in control of noise regulations, specifically on those applicable to the work environment. These directives have been developed to protect employees from harmful side effects of their working conditions, firstly targeting high noise levels generated by heavy machinery in industry. Nowadays, noise control regulations are widely effective and applicable to nearly all working environments, including institutions dedicated to the arts, such as opera houses. To the latter, directives on noise control are of major concern as opera performances tend to generate very high sound levels, especially in the area of the orchestra pit – the sunken space between stage and audience. In such context, management faces a difficult task conforming to noise regulations as they must balance the sometimes competing demands to (i) dutifully protect their employees – musicians and others – from any harmful ‘sounds’ or ‘noise’ that might be generated, and (ii) deliver world-class operatic art for the public, where noise regulations might compromise the culture of the art form. ‘Sound’ and ‘noise’ are two terms of intense interest when dealing with control of noise regulations in the entertainment sector. Indeed, noise is generally described as ‘unwanted’ sound, judged as unpleasant, whereas music is considered most of the time as a ‘desirable’ and pleasant sound; leading to a debate on the pertinence of noise regulations within the musical arts. Such debate has recently been discussed in the High Court in London, where the court favoured an orchestral viola player who claimed to have suffered noise induced hearing loss during a rehearsal of Wagner's Valkyrie1; the major argument being that the opera house exceeded industry-wide standards on noise control, viz. daily LAE > 85 dBA. Such a case has no precedent in UK history, raising concerns for other opera houses and music spaces on how to enforce noise regulations without affecting the performances’ nature. This leads to the question of whether noise control regulations should apply to all industries, regardless of the type of sound they generate