Suitability of HI-FI sound systems in measurements of reverberation time in domestic multi-media rooms

Reverberation time measurements are taken as part of the acoustic design of residential performance rooms such as home cinemas, listening rooms and studios This study examines the suitability of using Hi-Fi sound systems for the reverberation time measurements in domestic multi-media rooms Seven residential rooms were measured for reverberation time (T20) following ISO 3382-02-2008 using in turn a dodecahedron source, and Hi-Fi loudspeakers as the excitation sound sources. Tests used gated pink noise as well as integrated impulse response methods and results were compared. Overall T20 results from both sound sources agreed within 5% from 500Hz upwards, remaining very closely aligned as the frequency increased. A discrepancy of around 10% was observed between results obtained from both methods regardless of sound source employed This study showed that Hi-Fi loudspeakers can be a suitable and reliable sound source for reverberation time measurements in multi-media domestic rooms. This finding can give confidence in the use of existing Hi-Fi loudspeakers installed in domestic rooms to aid in their interior acoustic design

Review of Test Procedures for the Characterisation of the Acoustics Properties of Alternative Ventilation Ducts

In recent years there has been a surge in the use of alternative ducts for residential ventilation in lieu of galvanized steel ducting. This is mainly owed to cost, installation and other practical benefits afforded by alternative ducts. However, to date there is no information on the acoustic characteristics for these types of ducts to enable accurate prediction of noise transfers for such systems. This lack of reliable information often leads practitioners to make crude estimations or base their calculations on galvanized ducting acoustic data. These approximations can result in over attenuated designs which use unnecessary silencers introducing additional cost, regenerated noise and inefficiency. Designs that result in under attenuated systems will require costly retrospective mitigation measures. The ongoing research aims to fill that knowledge gap by characterising the acoustic properties of alternative ventilation ducts as used for the residential ventilation systems. In a prelaminar review of the literature, no harmonised and verified methodology was found for testing the acoustic performance of ventilation ducts and their systems elements. As a part of the research, a thorough review and analysis of all current testing methodologies used in the industry and in research is being carried out. The review involves an industry wide consultation to learn the different aspects of test methodologies employed. This will enable the development of a robust industry-accepted and standardised test methodology. A brief literature review and analysis of relevant test methodologies and procedures will be presented as well as results from the industry wide consultatio

Non-Special Loudspeakers as Speech Test Sources in Natural Acoustics Speech Intelligibility Investigations

Objective speech intelligibility estimations undertaken in natural acoustics speech communications (NAS) scenarios require the utilization of a speech source that approximates the acoustic characteristics of a human talker. Only a limited number of special speech sources that conform to the specifications in the relevant guidelines are available in the market; however, they can be deemed expensive by professional practitioners and other users. Non-special and affordable loudspeakers are often used in NAS investigations in place of standardized special speech sources without the knowledge of their suitability and results validity. This study aims to examine the suitability of a range of representative common and affordable non-special loudspeakers as a potential alternative to standardized speech sources in NAS indicative or pilot investigations. Frequency response and Speech Transmission Index Public Address (STIPA) experimental results obtained from a reference standardized speech source were compared against results from various non-special loudspeakers measured utilizing diverse and real-world representative combinations of NAS acoustic conditions under controlled laboratory conditions. STIPA mean absolute errors for the alternative speech sources were generally lower than the STIPA method uncertainty and one Just Noticeable Difference (0.03 STI). The findings of this study will inform practitioners of the suitability of affordable loudspeakers when standardized special test loudspeakers are not availabl

Towards introducing basic acoustic education in the performance music curriculum

Performance musicians, composers and conductors complete their extensive musical training without basic understanding of the fundamental acoustics concepts behind their practice, making their teaching and learning arguably incomplete

Design and Optimisation Of Voice Alarm Systems for Underground Stations

Voice Alarm systems (VA) are an essential part of subsurface underground station emergency and evacuation systems. Their main purpose is to assist in the management of emergency situations and evacuation procedures by providing key verbal instructions to the occupants. However these life-critical systems will be ineffective if the messages broadcast are unintelligible. Unfortunately, in most London underground subsurface areas the announcements broadcast by the VA system are not adequately intelligible and often do not reach a minimum specified performance target. The performance of VA relating to its electro-acoustic characteristics is relatively complex and depends on multiple interrelated factors and operational constraints . Underground stations present complex geometrical and architectural features which severely challenge the achievement of satisfactory performance. Despite the importance of VA system, there are few works in the literature providing practical and applicable design knowledge in the context of real world underground spaces. Moreover contractual performance requirements are not suitably laid out and this can lead to ineffective designs. This research aims to provide practical design knowledge and understanding for the improvement of VA speech intelligibility performance in underground spaces. Research results were derived from measurements and designs undertaken for real scenarios. A specific knowledge base is provided on the acoustics of underground spaces, speech intelligibility and VA systems. A critical review of relevant research and performance specifications and standards is undertaken and a new performance design parameter is proposed. An empirical prediction model tool based on a large pool of measured survey data is developed for the prediction of the Speech Transmission Index of VA on platforms. A validating and comparative study is undertaken for two widely used commercial acoustic simulation programs to assess their suitability as design tools for VA systems on platforms, CATT-Acoustic and Odeon. The impact on VA performance of design variables are investigated using a computer simulation of a representative platform. A novel acoustic treatment design concept is proposed. The Yang quasi diffuse sound field theory for platforms is verified and derived knowledge expanded. Practical design recommendations are provided as well as suggestion for further work

Dry wall construction workshop for acousticians

On Wednesday 27 September 2017, the Institute of Acoustics, London Branch delivered a pilot one day workshop for acousticians to have a better appreciation of drywall construction issues and their impact on sound insulation performance. The idea came from the observation that acoustic consultants to the building industry seldom have experience of practical issues of on-site installations. Eugénie's training in architecture included hands-on building work, which she felt valuable in her role as an acoustician. She wanted to give her peers their own opportunity to physically build partitions to undertand builders' constraints and become more proficient in reading technical drawings

The need for acoustics education in performance music syllabi

Acoustics is the underlying physical phenomenon and vehicle of music composition, performance and reception. It affects the perception of performers and other listeners such as audiences and conductors

Acoustic wave propagation through eco-friendly porous panels at normal incidence

Human and non-human subjects are exposed to micro plastics through drink, food, and air. Micro-plastics propagating through atmosphere are breathable particles during inhalation and exhalation leading to deposition of them in the deep lung via the alveoli of the lungs. Teabags are made of plastics that are not recyclable and biodegradable. Therefore, we intend to remove used teabags from the natural environment by repurposing them to make sound attenuating panels for building and architectural industries, contributing in this way to a sustainable circular economy. The panels were designed and developed from consumed teabags as porous material by filling a frame to investigate acoustics wave propagation through them at normal incidence. Experimental testing was carried out on circular teabag panels in an impedance tube using a transfer function method to determine their sound absorption coefficient and transmission loss. Furthermore, the impedance gun method was used to determine the absorption properties of square panels. Results show that 75 mm thick circular panels give an absorption coefficient higher than 0.8 between 400 and 1600 Hz. Up-to 9.8 dB sound transmission loss of circular panels is obtained at higher frequencies. Absorption coefficients for square teabag panels are very good despite a coincidence-dip seen at 800 Hz. The satisfactory sound absorption and sound transmission characteristics of acoustic panels made of consumed tea bags can make this recycled material a cost-effective solution in the production of sustainable acoustic treatment in indoor spaces. The results suggest that recycling of consumed teabag as the panel could be applied as alternative sound absorbing materials

London Battersea Heliport Noise Subjective Survey

A subjective survey in the form or an online survey questionnaire was designed and implemented to collect information on the perceptions and attitudes of local residents from noise emissions from the London heliport operation. The subjective study was intended to complement the objective study (reported in a separate document) and to allow a comparison of findings between the two. The questionnaire opened on 11 th July 2017 and closed on 30 th September 2017. It collected responses to mostly closed ended question from the boroughs of Wandsworth, Hammersmith and Fulham (H&F), Kensington and Chelsea (K&C). The survey questionnaire obtained a high (N=1570) participation rate. The level of annoyance caused by helicopter noise reported by respondents appears higher than the level of annoyance attributed to noise measurements at monitoring sites (see noise monitoring survey report). However it is important to note that many non-acoustical factors (such as location time of the day, socio economic factors) may influence when expressing attitudes and perception (annoyance). The proportion of respondents highly annoyed (%) by helicopter noise in this study was much higher than the proportion of highly annoyed to aircraft noise reported in a similar survey responded in 2014 by residents living around English airports. The current complaint handling and recording system appears to be ineffective and underrepresent the true scale of the impact on affected residents of the noise emissions from the heliport operation

Passenger noise exposure in London underground

The London Underground network carries almost half of London's commuters, and is the most heavily used mode of public transport in London. Its routes are 402 km long in total and it is used by over 1.2 billion passengers annually1. Though very efficient and convenient, travelling by Tube can be a noisy experience which could have potential impact on commuters’ hearing health. There is a wealth of research and information on impacts of occupational noise on hearing health. However, there is very little known on the potential impacts of transportation noise on passengers’ hearing health. The aim of this study is to determine and assess potential noise induced hearing loss caused by commuting on the London Underground when various practical noise exposure scenarios are considered