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.

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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.

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).

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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.

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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

A brief history of electroacoustics, pt. 7:
Loudspeaker enclosures

Reis’ telephone was perhaps the first loudspeaker of any kind, as it employed a magnetostriction driver mounted in a resonating box. But it would still take many years before inventors discovered the virtues of baffles and enclosures. As Hunt puts it, the baffle is probably the most frequently rediscovered feature of loudspeaker art. Stokes, in 1868, pointed out that the radiation efficiency could be improved by preventing air circulation around the edges of a vibrating surface (the acoustic short-circuit). Rayleigh, a few years later, gave the now classic analysis of the radiation from a piston in an infinite baffle. But by the time loudspeakers were being produced in great numbers, Rayleigh’s Theory of Sound had been out of print for more than two decades, and many inventors discovered the baffle before they discovered Rayleigh.

Read more…A brief history of electroacoustics, pt. 7:
Loudspeaker enclosures

Ørepluggenes ufortjent dårlige rykte

De siste årene har det vært et økt fokus på hvordan musikkspillere kan skade hørselen. WHO gikk i vår ut og sa at over 1 milliard ungdommer står i fare for å få hørselsskader som følge av for høy musikk på ørene. I den forbindelse har det stadig vekk vært slått opp i media, både nasjonalt og internasjonalt, at man bør unngå å bruke øreplugger, såkalte «earbuds» eller «in-ears».

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A brief history of electroacoustics, pt. 6:
Various loudspeaker mechanisms

The invention of the telephone set off a wave of creativity, and almost all conceivable transducer mechanisms were tried out in the 1870s and 80s. Some of them developed into usable devices, others serve mainly as illustrations of man’s creativity. In this part, some of them will be presented, ranging from useful, mainstream designs to the downright bizarre.

Read more…A brief history of electroacoustics, pt. 6:
Various loudspeaker mechanisms

A brief history of electroacoustics, pt. 5:
Moving coil loudspeakers of lasting impact

In Part 4, we looked at various early variants of moving coil (or moving conductor) loudspeakers, including predecessors of the modern moving coil cone driver. In this part I will present two specific designs that made a lasting impact on loudspeaker technology. One is a direct radiator; the other is a horn driver.

In the early part of the 1920s, many researchers were working on loudspeakers, based on various principles. E.C. Wente at the Western Electric Engineering Department (to become the Bell Telephone Laboratories) worked on a small direct radiating moving coil loudspeaker that was later patented (US patent 1812389, filed April 1, 1925 and granted the same date 1935). In England, Paul Gustavus Adolphus Helmuth Voigt at Edison Bell also worked on moving coil loudspeakers and microphones. In May 1924, he applied for a patent on a moving coil loudspeaker, but unfortunately a little to late. He was beaten at the finish line by two engineers at the General Electric Company, C.W. Rice and E.W. Kellogg.

Read more…A brief history of electroacoustics, pt. 5:
Moving coil loudspeakers of lasting impact