Hearing on both sides - Why do we have two ears?

The binaural hearing functions and their advantages easily explained

Humans generally have two ears - and for some hearing functions, both have to work simultaneously.

Is your cell phone ringing, but you can't remember where you last put it down? If you can hear with two ears, then you can probably also hear from which direction the ringing is coming.

In principle, we can also hear, understand speech and communicate using spoken language with just one ear. But with two functioning ears, we can hear in three dimensions, so to speak, and everything sounds fuller and more vivid. We can determine the direction of a sound source, we can concentrate on a specific direction and we can hear equally well from all sides. Skills that give us clear advantages in everyday life: Hearing becomes more reliable; listening becomes easier and more comfortable. Listen to a conversation in a pub as an example.

A cochlear implant on the deaf side can largely restore binaural hearing functions. A bone conduction system or implant on the deaf side can partially restore binaural hearing functions. In many cases, the combination of hearing aid and cochlear implant is effective.

Listen from all directions

As a rule, sound spreads in all directions, even around corners. However, there is also a so-called sound shadow: Behind an object, a sound can no longer be heard or is clearly muffled. Whether an object casts such a sound shadow depends on the dimensions of the object and the pitch of the sound. This is how soundproof walls work, for example. But our head also casts a sound shadow. While low-pitched sounds can easily get around our head, the human skull becomes an obstacle for higher-frequency sound components.

People who are deaf on one side do not realize when someone speaks to their hearing impaired side. Or they can hear what is being said but cannot understand it because some sounds are missing. Even if warning signals come from the deaf side, these are sometimes not perceived, only indistinctly or with a delay.

Understanding speech with background noise

In the central auditory system in the brain, the signals from both ears are compared with each other and shifted in time, i.e. delayed slightly if necessary, so that we can concentrate on a particular direction. This allows us to block out noise from other directions. People who can hear well on both sides can still communicate with each other as long as the background noise is not more than twice as loud as the volume of the conversation.

Most everyday conversations take place with more or less ambient noise: People are also talking at other tables in a restaurant, there are several conversations going on next to each other in a group, there is music playing in the shopping center, in the office, on the street, there is background noise everywhere. Easy speech intelligibility is particularly important when there is background noise at school.

Directional hearing

We only hear with both ears at the same time if the sound source is directly in front of or behind us. If sound comes from the side, it first reaches the ear facing us and then, with a minimal delay, the ear facing away. This minimal time difference varies depending on the direction of the sound source - our central auditory system can recognize the direction of the sound source from the time difference.

With only one hearing side, this is only possible to a limited extent. That can be annoying when I'm looking for the ringing phone. It can be annoying during group conversations when I have to search for who exactly is speaking. But it can be dangerous if I can't hear which direction the sound of an approaching car or the ringing of a bicycle bell is coming from.

You can also learn about the difference between hearing with one or two ears in the first three parts of the interactive game "Switch on Life".

Deaf or hard of hearing in one ear: you can avoid these problems!

Each ear with hearing problem should always be adequately supported. For children or adults with unilateral hearing loss or deafness, a suitable hearing system for the affected side and for those with bilateral hearing loss for both sides! Bimodal treatment is sometimes used for hearing loss of different severity: a hearing aid on one side and a cochlear implant on the other.