“Every person constantly encounters sound. Without sound there would be neither communication nor music”, says Peter Balazs, director of the Acoustics Research Institute of the Austrian Academy of Sciences (OeAW) in Vienna. Although sound is so common and was already studied by Pythagoras, there is still a lot for researchers to do. “We mainly work with sound in the everyday sense, i.e., a longitudinal wave that spreads as pressure differences in the air. The basic principle has long been understood, of course, but the field is so broad that we are far from finished”, Balazs says.
There are open questions, among other things, about the storage and visualization of sound signals, the simulation of sounds and possible therapeutic approaches for people with partial or complete hearing loss. “There is still a need for basic research in all areas, from sound generation to its propagation and perception. We therefore pursue an interdisciplinary approach at the institute, between mathematics, physics, biology, music, linguistics and psychology”, Balazs says.
Sound as a tool
With this approach, the researchers have developed a new way of visualizing sound signals. Such tools can be used to better analyze the relevant data, for example to examine materials for weak points. In addition, the scientists are working on improving cochlear implants, which allow some people with total or severe hearing damage to perceive and understand acoustic signals again.
Everyone hears differently because the pinna and the auditory canal are unique.
“How sound is perceived is very interesting. Everyone hears differently because the pinna and the auditory canal are unique. This also helps us to determine where a sound source is, because the signal spreads in a certain way in the ear depending on the direction. Of course, we recognize left and right mainly by the difference in signal delay and volume between our two ears”, Balazs explains.
Budgerigars and octaves
How people perceive sounds is also the subject of active research. “We are trying to find out, for example, whether we can reconstruct a natural listening experience in headphones that also allows the localization of sound sources. If you try this with headphones, then the sound often seems to be coming from in your own head”, Balazs says. In addition to a natural listening experience, the quality of the sounds also plays a role in research. Large companies now meticulously design the sounds that products make. “Sound can transport emotions very quickly. Large car companies spend a lot of money developing the noise that a car door makes when it closes”, Balazs says.
We know that people perceive octaves as similar tones. We have found that this is not the case with budgies.
With music, the question arises as to which listening habits are learned or cultural, and which ones animals can also have. “We know that people perceive octaves as similar notes. We have found that this is not the case with budgies”, Balazs says. The production of music in the laboratory is somewhat simpler. Machine learning is used to fill in errors in pieces of music, like those resulting from scratches in a record, so that the listener does not notice them. “This works very well even for long disturbances if the listeners are not experts in the music concerned”, Balazs says.
Music and noise
In a next step, algorithms that are capable of learning can also make music themselves. “For instance, we try to solve the digital synthesis of opera singers that way. An algorithm that has learned how to sound like Pavarotti could then sing, for example, ‘Enter Sandman’ from Metallica”, Balazs says. From a scientific point of view, how noise differs from, for example, music is difficult to answer objectively. “I have carried out surveys with examples here at our open day for the International Noise Awareness Day and have never got uniform results”, Balazs says.
Sound can also cause damage. With loud sounds, damage can be done very quickly. Long-term, moderate noise pollution can result in stress and thus also physiological problems.
Noise can be defined as “unwanted sound” and is also the subject of research at the institute. “Sound can also cause damage. With loud sounds, damage can be done very quickly. Long-term, moderate noise pollution can result in stress and thus also physiological problems. To assess the risk, we need to know more about how sound is generated, propagated, perceived and how it can best be modeled and calculated”, Balazs says.
If your curiosity has been aroused and you want to know more about sound, then the International Noise Awareness Day is on April 29, 2020. Numerous stations at the Acoustics Research Institute of the OeAW invite adults and children to join in and listen.