The new lab mimics the sound of any room
Researchers at Aalborg University, in collaboration with Bang & Olufsen in Denmark, have developed a sound lab capable of reproducing the acoustics of any environment, from cars to concert halls. One of the goals is better design of audio systems for cars.
In the basement beneath Aalborg University are 40 small loudspeakers and three subwoofers placed around a narrow walkway with just enough room for a chair. The space is an anechoic chamber where the walls, ceiling, and floor are covered in thick, pointed sheets of foam that absorb sound that hits the walls.
The 43 loudspeakers are configured in such a way that with a newly developed recording system and an advanced computer program, they can reproduce the exact acoustic conditions of any other room. If you insert a CD into the drive or play an audio file on a computer, it will sound entirely as it would in the space simulated by the lab.
The sound laboratory is the latest in the faithful reproduction of acoustic conditions. Years ago, Aalborg University together with Brüel & Kjær, Delta Akustik and Bang & Olufsen developed an artificial head with built-in microphones that could record how the human ear perceives sounds from different places. The artificial head was then developed to rotate to either side and accurately map how room acoustics affect sound as you move.
By playing sound through a pair of headphones with a head-tracker, you can make it sound like you’re in the room. Perceived acoustics are very close to those of the real room, so you can simulate how speakers and audio systems work in different rooms.
Not the same with headphones
Recordings with artificial head technology have been used for a number of years to reproduce various acoustic conditions, but the problem has always been that we don’t usually experience the sounds of our surroundings through a pair of headphones on a daily basis. In order to more accurately reproduce an acoustic environment, you can greatly enhance the experience by using a speaker setup in an anechoic environment to create an accurate spatial illusion. The idea and system was originally developed by researchers at Aalto University in Finland for studies of sound in concert halls. The AAU system is an advancement intended for small spaces such as living rooms and automotive interiors.
“With headphones it often feels like all the sounds are pretty close or inside the head. You don’t feel like anything is coming from further away – the spatial element is very difficult recreate”, explains doctoral student Neo Kaplanis. who developed the new sound reproduction system at AAU.
“The same goes for the experience of a powerful bass. It’s not something we just hear with our ears; it’s something that can be felt throughout the body. not reproduce it with a pair of headphones. However, in the precise positioning of speakers in the new sound lab, you can. Using recordings made with the appropriate recording method, we can recreate the sound of any room. If you’re wearing a blindfold or turning off all the lights in the lab, your ears are telling you that you’re in a completely different place; in fact, that’s how we conduct the experiments,” explains Neo Kaplanis.
Better sound in the car
Right now, the lab is designed to replicate the acoustic space of a car, and for good reason. The university’s partner, Bang & Olufsen, was until recently one of the world’s leading manufacturers of Hi-Fi audio for luxury cars. The automotive department was recently sold to American loudspeaker manufacturer Harman, but their development department is now located in Struer, right next to B&O headquarters.
When you develop an audio system for a brand new car, it takes a lot of time because you are testing the car with many different speaker systems that need to be changed along the way. It’s a long and expensive affair, but since all new car production is top secret, audio system manufacturers usually only have a prototype of the car available for a few days.
“With the new system, we will be able to map the acoustic conditions of the car, send the car back to the factory, and then adapt and adjust the audio system with measurements in the laboratory. This makes it possible to develop a much better sound quality.” says Søren Bech, director of research at Bang & Olufsen, who divides his time between the Struer company and a professorship in the Department of Electronic Systems at AAU.
The possibilities of the sound lab are not limited to the best speaker solutions for luxury cars. With the new system, we can in principle reproduce the sound of all kinds of spaces, from concert halls to living rooms, including buildings that are still on the drawing board. The installation will therefore be an important tool in future research/development projects.
- Audio systems are a big selling point in luxury cars. In partnership with Bang & Olufsen, car manufacturer Audi has mapped the acoustic conditions in most model series. Potential buyers can put on a pair of headphones and virtual reality goggles and click through the interiors – and soundscapes – of different cars.
- A scientific paper by the researchers presented at the 60th International Conference of the Audio Engineering Society in Belgium earlier this year describes the design and implementation of a method to perceptually assess the acoustic properties of a car interior and subsequent sound reproduction properties of automotive audio systems. Read more: http://vbn.aau.dk/da/publications/a-method-for-perceptual-assessment-of-automotive-audio-systems-and-cabin-acoustics(901487d0-014d-4b45-96be-5678443656ef).html