About Sound

The speed of a sound wave is measured as a "frequency", which is also called "pitch" in music. When we make a deep sound (like the sound a tuba makes), the sound waves vibrate slowly. The frequency is low and the sound is called "low-pitch".

When we hear a high-pitched sound (like birds chirping), the sound waves are vibrating fast. This means the frequency is high.

The "size" of a sound wave is called "amplitude". The amplitude determines how loud the sound is. A loud sound has a high (big) amplitude.

A quiet sound has a low (small) amplitude.

The outer ear

The outer ear, also called the "pinna", catches the sound wave and funnels it through the ear canal. The human pinna is pointed forward. Therefore, we hear sounds in front of us better than sounds behind us. Many animals, such as cats and dogs, can move their pinna. In this way, they can focus on sounds from any direction, just by moving their pinna.

The eardrum marks the boundary to the middle ear. It is stretched tight, just like the skin of a real drum, and it is very sensitive.

Another job of the eardrum is to stop noisy, low-pitched background sounds that come in through the ear canal. The eardrum takes these away so that we can concentrate on more important sounds such as what people are saying. This helps us keep conversations going even when we are in a loud place like on a busy street or on a bus.

The middle ear

The three tiny bones in the middle ear are called ossicles, or the ossicular chain (because they connect up to one another like links of a chain).

The hammer is connected to the inner wall of the ear drum. On the other side, the hammer is attached to the anvil. The anvil is connected to the stirrup on the other side. When sound comes in and makes the ear drum move, the ear drum pushes on the hammer and the three bones of the ossicular chain start to move. In this way, vibrations from sound travel all the way to the inner ear through the ossicular chain of the middle ear. The ossicles are pushed harder for louder sounds and softer for softer sounds.

The inner ear

The inner ear is the most complex part of the ear. The cochlea is the part of the inner ear that is responsible for hearing. But there is another system at work in the inner ear, too. Next to the cochlea, there are 3 arches filled with fluid. This part of the inner ear is called the vestibular system and it is actually responsible for the sense of balance.

The fluid in the inner ear passes the sound vibrations on to the tiny hairs which sit on top of the fine fibres called hair cells.

The hair cells have the important task of making electrical signals out of the movement of its hairs. This is important because electrical signals are the way that sound travels to the brain.

Since the hair cells are connected to the hearing nerve, the electrical signals are able to travel through the hearing nerve to the brain. That is how the brain finally receives sound.

Our amazing brain works like an enormous computer. It can analyse the signals from both ears so that we can determine from which direction the sound is coming. Also, our brain makes us understand speech and music and allows us to memorise sounds.