Was ist eine akustische Täuschung?

What is an auditory illusion?

Maybe you know that you can't always rely on your sensory perception 100%. Surely you know the typical phenomenon of optical illusion. Also a Fata Morgana is surely a term for you. Here the illusion of proportions or spaces is created. There are also intentional representations, which are used, for example, very popular in art, on postcards or in calendars.

Much less known, however, is that there are also acoustic illusions. The sounds that you perceive from your environment, you sometimes interpret quite differently than they are in reality. In our guide, you'll learn about some examples of this.

Hidden tones

It happens that you can hear two tones at the same time, which differ only very little in terms of pitch. Then you consciously perceive only the louder stimulus. The decisive factor is that one of these two tones is much louder than the other.

The clever inventors of the MP3 format took advantage of this acoustic illusion. When music is played, some of the sounds can simply be omitted. After all, humans hardly perceive some sounds anyway. This plays an important role in digitization. Data transmission is also affected in the process. The smaller the files, the better. After all, then only a minimal amount of space is needed to store music files or transfer them faster on the Internet.

The acoustic phenomenon of the Shepard scale

The so-called Shepard Scale deals with an acoustic phenomenon in which multiple targets are played simultaneously. The sounds are different in the process. Because the volume changes however temporally shifted, you have as a listener the feeling, you would hear a scale. In reality, however, you only hear the same tones, and each of these tones has a different volume. You can find many beautiful sound examples on the Internet. Some of the effects you can perceive are very futuristic. Artists also imitate this illusion, for example in piano pieces. This phenomenon is sometimes even used by organ pipes in certain melodies. This creates a very floating sound experience.

Melodies with a mysterious background

Diana Deutsch is a well-known American music psychologist. She has found in her studies that it is usually not possible to recognize randomly chosen fragments from a melody without a coherent context. However, once the subject has heard the complete piece of music, it is possible for him to deduce the entire melody from the fragments. Your brain can fill in the missing passages as needed. In your head, you then hear the whole song, although you can only perceive individual notes of it.

Spatial sound effect through stereophony

A special spatial sound effect can be created with the help of stereophony. Basically, only two different speaker systems are needed for this, which reproduce the sounds. With a clever control, the illusion is created that the sound source would be somewhere else in the room than is actually the case. This special effect is often used in the cinema or at a concert.

With 3D animations, it becomes particularly interesting. This is because a spatial image is then added to the optical illusion. The prerequisite is that the sounds are placed in exactly the right place. You feel the resulting impression as even more realistic, and sometimes you can almost no longer distinguish between film and reality.

The special McGurk effect

Do you know for sure that you can hear exactly what someone is saying? If you are really so sure, you can try it once with the McGurk effect. This is a very interesting acoustic illusion: An auditory experience is superimposed by the optical perception. The decisive factor is always which movement the speaker makes with his mouth. You then actually believe that you are hearing different words. The deposited sound sequence, however, does not change at all.

With this effect, you find that you can even read lips unconsciously, but for accurate recognition you need some practice.

The tinnitus as a delusion

One of the best-known and most unpleasant acoustic illusions is tinnitus. This is actually pure phantom sounds in your ear. You can hear them, but they do not really exist. Tinnitus can be very disturbing for you. Especially when the tinnitus turns out to be permanent, it becomes really uncomfortable.

Triggers for tinnitus include:

  • accidents
  • Trauma to the hearing due to short- or long-term overuse
  • Stress

Different treatment approaches may be considered for tinnitus, such as drug, psychological or physiological therapies.

A hearing aid can also contribute to the successful treatment of your tinnitus