Loudness is measured in decibels (dB) and is the change of air pressure created by a sound wave. The bigger a sound wave, the more energy (intensity) it carries and the louder the noise. The smaller the sound wave the quieter the noise. 

Extremely loud noises can create so much pressure they can damage the hearing. The closer we get to the source of the sound the higher the intensity of sound.

The height of a sound wave is called amplitude. Waves with higher amplitude have higher intensity. Different levels of loudness are created by different amplitudes.

The quietest sound our ears can detect measures 0 dB. When we speak our voice tends to be between 50 dB and 60 dB. When babies cry it’s around 110 dB. Sounds louder than 120 dB can hurt the ears. 



The launch of a rocket can be up to 190 dB! That’s so loud it can permanently damage someone’s hearing. 

 

Amplitude

When sound waves reach our ears they put pressure on our eardrums. Louder sounds push harder against the eardrums. This pressure is measured as amplitude. The louder a sound the greater the amplitude. When sounds reach 120-140 decibels it can be painful. Very loud music can even cause temporary or permanent damage to our hearing.



Pilots wear special headphones to reduce the sound of the aeroplane’s engines. Each earpiece has electronics that produce sound waves with the exact opposite shape as those coming from the engine, this cancels out the noise protecting the pilot’s hearing.