Waves - 6.1.4 Sound Waves (Physics Only) (HT Only) (GCSE Physics AQA)

Sound Waves (Physics Only) (HT Only)

Travelling Through Solids

• Sound waves are longitudinal. Sound waves are longitudinal waves, which means they vibrate in the same line as the wave direction. These waves can travel through solids.

• Sound travels at different speeds. Sounds can travel at different speeds in different substances. Sounds travel fastest in solids, and slowest in gases.

• Particles must vibrate. Sounds need particles to vibrate and carry the wave. They travel by causing vibrations in the solid. This is why sound waves cannot travel in space.

Human Hearing

For AQA exams, you need to know about the process of human hearing.

• Sound waves reach the ear drum. When sound waves travel through the air, they will reach the ear drum. This is the first step in human hearing.
• Sound waves convert into ear drum vibrations. Once the sound waves have reached the ear drum, they will make the ear drum vibrate. The vibrations pass through the ear drum, causing bones to vibrate.

• Signals are sent to the brain. As the bones in the ear vibrate, the vibrations pass through a series of structures in the ear. Eventually these vibrations will reach the brain in the form of electrical signals. These electrical signals allow you to ‘hear’ the sound.

• The process works over limited frequencies. This process of hearing in humans will only occur over a limited frequency range. Since the frequency range is limited, this means that humans can hear some sounds but not others, so we are said to have a restricted range of hearing.

Frequency Range

• The range for hearing is 20Hz to 20kHz. In the human ear, the frequency range is between 20 Hertz and 20 kiloHertz. We could also say this as 20-20,000 Hz. This is the normal human hearing range. The human ear hears best at about 3,000 Hz.
• Frequency is limited. The frequency range of human hearing is limited to the values described above. The reason behind this is due to the shape and size of the human ear. It is relatively small, meaning that it can only transfer a certain amount of energy without being damaged.