Two Ears Come As Standard Equipment Why hearing well with both ears is crucial, naturally and with aids

Read more Last updated: November 2019
In collection Kids
Reading duration: 4 minutes

If both ears are out of action, daily life becomes rather complicated. Even if only one ear gives out, a crucial ‘something’ is missing.

Directional hearing

Where does that sound come from? Left or right? Up or down? For people with normal hearing, locating sound is as easy as kicking a ball is for footballer David Beckham. But for someone who has hearing only in one ear, it is difficult to locate a mobile phone in a room from its sound alone.

This is also the case for anyone who suffers from impaired hearing in both ears, but only wears a hearing aid or implant in one of them. Determining the location of a sound is simple with the joint help of your eyes and ears. With both ears open and your eyes closed, it is still easy to pinpoint it. But close your eyes, put a finger in one ear and ask someone to click their fingers different places around the room, and you will find it hard to know where the sound is coming from.

Binaural hearing

Built-in stereo

Identifying the source of a sound can only be determined properly with two functioning ears. Experts call this skill ‘spatial hearing’ or ‘sound localisation’. For example, when a sound is generated on our left side, it arrives sooner at the left ear. It is also louder than on the right because the head acts as a buffer, as the sound travels to the other ear. This is known as the ‘acoustic shadow’. From all these subtle forms of information the brain identifies the source of the sound and we can orientate ourselves.

There are other reasons why we are born with two ears – loudness is almost doubled. While we may be able to hear a sound from 10 metres perfectly with two ears, it can be less easy with only one. This natural amplification is known as ‘binaural summation of loudness’. With two ears, background noise can be filtered and toned down. In this way we can understand each other, even in a packed restaurant with people telling stories, laughing, discussing and ordering food. This can only work because sound waves at varying intensities reach our ears at different times. From this sound cocktail, the brain can determine which message is wanted and which to reject.

Music is better appreciated with two ears than with one. The sound is fuller, more spacious and rich. The stereo system works on the basic principle of two speakers generating sound to create a feeling of space. Our ears work in a similar way – acting as our built-in stereo system.


About Hearing

Explore MED-ELs animated guide to how hearing works and learn more about the different types of hearing loss.

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Origins of speech

Whilst hearing is important in every adult‘s daily life, it is even more crucial for infants who are only just beginning to understand what their parents are talking about and how their mothers tone of voice changes when she is cheerful or tired. They learn to distinguish one sound source from another and realise that stamping on a wooden floor sounds different from on grass, that a feather falls silently, whilst an iron crashes down with a loud bang.

The brain learns to perceive information with both ears and to interpret it. With each sound that the developing brain takes in, new neural connections are formed, just as with every other learning process. The nerve tracts in the brain grow, join and become more stable. All this happens before the child has even spoken a single word.

Speaking starts with hearing. Only when we hear can we develop spoken language. Two ears are ideal, but essentially, one is enough, as long as the learning environment is quiet. Later, at school or university, things can become complicated. Classrooms can be loud, and auditoriums large. This can make it difficult to understand the teacher. We can get by with just one ear, but there are good reasons why we were designed with two. The use of both ears means a greater opportunity to take in essential information and have a greater awareness of our world.

Two girls helping each other to look over a fence
© Corbis

Two ears, two aids

If a person has hearing problems with both ears, two hearing aids or implants are beneficial. In many countries, this is becoming common practice, especially with children. Scientific studies show that hearing-impaired children benefit from a second device. If sound signals come in through both ears, the brain‘s hearing centre is optimally activated. Children learn to hear in a more natural way than with only one device such as a cochlear implant.

As a consequence, they have an improved understanding of speech and can express themselves better verbally. Using for example two hearing implants, as opposed to just one, leads to two clear benefits – children understand speech well, even in loud environments, and the localisation of sound is much improved. Parents report that their children are less tired after school, once they have been fitted with a second hearing implant.

Hearing With Only One Ear: Binaural Hearing vs. Unilateral Hearing Loss

What happens when you can only hear with one ear? This hearing loss in only one ear is often known as unilateral hearing loss or single-sided deafness.


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