Horn simulation using mode-matching

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

Proceedings of the 39th Scandinavian Symposium on Physical Acoustics

The 39th Scandinavian Symposium on Physical Acoustics was held at Geilo, Norway from January 31 to February 3, 2016. It was organised by Ulf Kristiansen and Erlend Magnus Viggen, both part of the Acoustics Research Centre. This year we had 48 participants holding 31 presentations, and 9 papers were written for the proceedings, which have been published through arXiv.org.

This link takes you to the proceedings.

Thanks to Sverre Holm and Josephine Børvan for the photo

ARC på NRK P2 for å snakke om stillhet

Sist lørdag tok programmet Ekko Helg på NRK P2 opp temaet stillhet. Som gjest hadde de filosof Kaja Melsom og vår egen Odd Pettersen. Både de filosofiske og de akustiske sidene av hva støy og stillhet gjør med oss ble dermed diskutert.

Du kan høre diskusjonen på NRKs nettsider, opptil seks måneder etter sending.

Bilde fra Microsoft Clip Art

App basert på lydteknologi fra SINTEF kan gi bedre hørsel

De tre norske gründerne Snorre Vevstad, Ralph Bernstein og Jørgen Myrland i Listen AS er i ferd med å lansere en ny hørselsapp. Appen er laget av SINTEF Akustikk og basert på vår erfaring innen hørselsteknologi og høreapparater.

I dag koster det mange tusen kroner å få et høreapparat, og det kan ta 6-18 måneder å få et godt tilpasset apparat gjennom det offentlige systemet. Listen AS ønsker å snu opp ned på dette markedet, med raskere og billigere tilgang til hørselshjelpemidler. På verdensbasis er det kun 10 % av de som trenger et høreapparat som har tilgang til det.

Appen har tre hovedkomponenter:

  • Hørselstest
  • Sanntidsprosessering av lydsignalet basert på resultater av hørselstesten
  • Fjernhjelptjeneste

Les hele artikkelen på digi.no.

Program of the 39th Scandinavian Symposium on Physical Acoustics

The 39th Scandinavian Symposium on Physical Acoustics will be held at Geilo Hotel from January 31st to February 3rd, 2016, and is organised by Ulf Kristiansen and Erlend Magnus Viggen at ARC. This year, there are 50 registered participants who will be holding a total of 32 talks on various topics such as sound propagation, ultrasonics, sonar technology, acoustics in solids, petroleum-related acoustics, and more. You can find the entire conference program below, and a printable version can be downloaded here.

Read more…Program of the 39th Scandinavian Symposium on Physical Acoustics

Presenting the MAUS project on traffic auralisation

In the MAUS project, we have developed a prototype of a traffic auralisation tool. The idea is to realistically imitate the sound of traffic, to give an idea of how it will sound in cases that have not been realised yet, and to show the effects of various noise-reducing measures. We have previously given a simple description of how the tool works together with sound examples on this blog.

In early December, we presented a paper and a poster on the MAUS auralisation tool at the 18th International Conference on Digital Audio Effects (DAFx-15) here in Trondheim. This conference was organized by the Music Technology and Acoustics groups at NTNU.

Read more…Presenting the MAUS project on traffic auralisation

Project: Next Step

Noise induced hearing loss (NIHL) is one of the most common occupational diseases. This is a fact even if most countries have legislations specifying how much sound employees can be exposed to. Therefore new models for NIHL seem to be necessary to reduce the risk of developing hearing disorders.

In the Norwegian petroleum industry much attention has been paid to occupational noise and hearing damage in the last decade. Statoil ASA has, in collaboration with Honeywell, been involved in several projects at SINTEF with this in mind. The current ongoing project is called Next Step (Noise Exposure Tackled Safely Through Ear Protection).

Read more…Project: Next Step

Hvor kommer lyden fra?

Lukk øynene dine og hør på lydene rundt deg. Kan du høre hvor de kommer fra? Hvilken retning, og hvor langt unna lydkilden er? Hørselen vår er et eksepsjonelt instrument som ikke bare har et stort dynamisk område, men også evnen til å lokalisere lydkilder. Vi kan faktisk oppfatte retningen til en lydkilde med en nøyaktighet ned mot én grad. Denne evnen er i stor grad mulig fordi vi ikke bare har ett øre – men to! Dette gjør at vi klarer ganske så godt å skille lyder vi er interessert i, typisk tale og musikk, fra uønsket lyd som kommer fra andre retninger.

Read more…Hvor kommer lyden fra?

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

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

A brief history of electroacoustics, pt. 8:
Horns: Early development

It is hard to tell when horns first were used. They have been in use for thousands of years as instruments, and man must early have discovered the amplifying effect of a pair of cupped hands in front of his mouth, or behind his ears. Ear trumpets were early implementations of this, and the first hearing aids.

Horns were used on phonographs and gramophones from the start. This was the only way to get the required volume from the tiny motions of the needle. The theoretical understanding of horns was still small though, and most of the work was experimental. Early models used conical horns, but as theory progressed, the superiority of the exponential horn was recognized.

Read more…A brief history of electroacoustics, pt. 8:
Horns: Early development