Acoustics Research Centre

Adaptations of CNOSSOS-EU to third octave bands

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CNOSSOS-EU is a new European calculation method for noise levels from road traffic, railway traffic and industry sources. The method is described in the EU Directive 2015/996. Its objective is to ensure that a uniform method is used throughout Europe to calculate noise levels for area planning and action plans to protect the populations’ health from excessive noise levels.

As CNOSSOS-EU deviates from the current noise calculation methods in Norway, this must be amended to fit current Norwegian policies. On behalf of the Norwegian Environment Agency (Miljødirektoratet) SINTEF has written a report that describes how 1/3 octave resolution can be introduced in CNOSSOS-EU which CNOSSOS-EU in its current state does not support. The report can be found here:

SINTEF-report-2021-00435-Adaptations-of-Cnossos-from-octave-bands-to-third-octave-bands

If you have any comments, feel free to reach out: acousticsresearchcentre@gmail.com

Please note that some of the coefficients have been updated in July 2021.

MobileEars: An app-based hearing aid

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A lot of people could use some help with their hearing, but getting a hearing aid has traditionally been a big, time-consuming, and expensive step. As we reported earlier, the Oslo-based company Listen have therefore been developing an app in collaboration with SINTEF that turns your iPhone into a hearing aid.

Their first app, MobileEars, was released this week, and is now available for free download from the App Store. You can see a promotional video for the app below the break.

Read more…MobileEars: An app-based hearing aid

Project: I Hear You! A new hearing service in Tanzania

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Sharleen is an African girl, 9 years old, from a family of farmers. She is quite smart, but no longer goes to school.

Why? 

Sharleen has a hearing impairment, and couldn’t understand what the teacher was saying. Her father thought he needed her at home to look after the goats. Unfortunately, Sharleen is just one among many children lacking help.

WHO has estimated that over 5% of the world population – 360 million people – has a hearing impairment (328 million adult and 32 million children), and the majority of children with hearing impairment live in low-income countries. In contrast, less than 2% of the hearing aids produced in 2005 went to low income countries.

Traditional hearing devices are advanced equipment; expensive, fragile and not developed for the Third World. Specialised personnel and complex infrastructure in the individual fitting process is needed, reducing the usefulness of such complex hearing aids to a minimum in low-income countries, where trained people and specialists are scarce.

With funding from Norwegian Research Council, SINTEF’s project “I Hear You”, starting early 2017, aims to help children like Sharleen by ensuring access to education for the hearing impaired.

Read more…Project: I Hear You! A new hearing service in Tanzania

Video: Take care of your hearing!

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Noise-induced hearing loss is a result of exposure to loud sounds over a long time, or to one extremely loud impulse. In addition to permanent loss of hearing, tinnitus is a common symptom. While this is the most common permanent injury in the world, it is also preventable through hearing protection equipment and safe working practices.

We have acted as scientific consultants for a new five-minute information video from Honeywell on this topic. You can see the entire video here!

Truls Gjestland, Fellow of the Acoustical Society of America

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Our very own Truls Gjestland has been elected a Fellow of the Acoustical Society of America, by action of their Executive Council. This honour was bestowed on Truls due to the contributions that he has made throughout his career to research and standards development on transportation noise effects on communities.

The formal announcement and Fellowship certificate presentation will be made at the ASA meeting in Honolulu, on 30 November 2016.

Horn simulation using mode-matching

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Horns are used in many fields, including musical wind instruments and loudspeakers. The physics in the two cases is of course the same: sound propagation in a flaring duct open at one end. Therefore we can in principle use the same simulation methods for both cases. But what we want to obtain from the horn simulation can be very different.

A very important requirement for horn loudspeakers is directivity control. This entails directing sound into a specific region in front of the horn, giving the same frequency response inside that region and little sound outside it. Any simulation method for horn speakers must be capable of predicting directivity. Horn speakers should not be resonant, but should present a constant and smooth acoustic load to the driving unit, so this is also an important, but somewhat less critical, factor in the design.

For wind instruments, we are usually interested in the resonance frequencies. This is important for the tone, intonation and playability, and it is useful if we can predict this when designing the instrument. Any simulation method must therefore be able to predict these frequencies accurately. Or we may have an old valuable instrument and want to find the internal shape without cutting it into pieces. Then we can use an optimization algorithm to solve the inverse problem of finding the internal shape from measured resonance frequencies. For this, the simulation method must be fast.

Read more…Horn simulation using mode-matching

A brief history of electroacoustics, pt. 9:
Horns: Cinema sound and large scale sound reproduction

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The 1920s saw much development in horn loudspeakers, and loudspeaker in general. Western Electric already had their microphones, amplifiers, straight exponential horns, and very good balanced armature transducers. At this time, much research was also put into disc recording and reproduction at the Western Electric Engineering Department, and simultaneously, optical recording of sound was also in progress, using Wente’s Light Valve. The time seemed ripe to attempt sound film. The story has been told elsewhere, but in short, most of the industry turned down Western Electric’s offer. They “knew” sound film would not work. But the Warner Bros found in the WE system something that could help them beat the big guys in the industry, and after the success of their first sound film, the rest is history.

Read more…A brief history of electroacoustics, pt. 9:
Horns: Cinema sound and large scale sound reproduction