With headphones on, it is often difficult to distinguish from which direction an external sound is coming. Researchers have now presented a filter that should help to better assess this. Through special structures, it restores acoustic modulations that reveal the source of a sound. This can be a major safety aspect in everyday life, especially when there are dangers in the blind spot.
Podcasts, music, phone calls: Many people use headphones on a daily basis and listen to music or conversations. However, this often leads to dangerous situations and accidents, especially on the road. This is partly due to the fact that headphones restrict the auditory perception of the outside world, making it difficult for the wearer to recognize the direction from which a noise is coming. In particular, the question of whether a sound source is approaching from the front or behind is almost impossible to answer with music playing.
The problem from the front and back
Scientists refer to this effect as “front-back confusion”. In particular, this confusion stems from the fact that the human brain can no longer rely on so-called “head-related transfer functions (HRTFs)” through the headphones. While it is relatively easy to determine from which side a sound is coming from the time difference between the left and right ear, the brain relies on empirical values to distinguish between front and back.
One of the ways the brain does this is by evaluating the HRTFs that are typical for different directions. These complex changes in the incoming sound are primarily related to resonance effects that occur when the sound waves interact with the head, body, and outer ear. However, these changes in sound quality are significantly influenced by the headphones, making localization more difficult.
Filter element reduces ambiguity
Researchers at the University of Ulm have now developed a filter element that can restore these modulations. Similar to a human ear, it is placed on the outside of the headphones around a microphone input, where it can reduce acoustic ambiguities, regardless of the spectral composition of the noise.
This is primarily achieved through the specifically shaped structures of the filter element. They influence the outside noise in such a way that spatially dependent frequency modulations arise. The resulting HRTFs then enable the wearer to precisely localize the sound source and thus resolve the “front-back confusion”.
Researchers see great potential
The Ulm scientists hope that in this way auditory objects in particular in the blind spot of the respective user can be better recognized, which would increase the safety of headphones in everyday life and on the road. In addition, it is possible to integrate the filter element in all different models such as circumaural, in-ear or even bone conduction headphones. The researchers see a future for filter elements, particularly in the market for innovative headphone designs that is likely to continue to grow.
Source: Technology License Office (TLB) of Baden-Württembergische Hochschulen GmbH
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