Basics of Sound

There is a reason why most objects surrounding us seem to generate sound. Running water, wind, cell phones, and voices are all examples of sounds that you hear on a daily basis and understanding the basics of sound is best achieved by getting familiar with sound waves.

The noises you hear around you are waves that travel through a medium such as air or water. These waves produce vibrations that run longitudinal to the direction they are travelling in, meaning that there is a back and forth motion happening in the direction they are travelling in.

A great example of how soundwaves work is when a smartphone receives a text message from a sender.

In this instance, the smartphone contains a diaphragm, which is a piece of cone-shaped material that has electronics inside designed to make the diaphragm move back and forth when it receives a text message.

During this movement, the atoms and the molecules in the air surrounding the diaphragm create a soundwave that works to spread out in a mini explosion. Physicists in the past have described soundwaves in terms of the movement of their particles in the air.

This movement has been defined as a Displacement Wave, which causes the surrounding air to expand and compress, while spreading outwards.

Soundwaves can be described as pressure waves because devices have been built to detect those changes in pressure.

Devices such as microphones use a diaphragm to sense soundwaves that create areas of high or low pressure that causes the diaphragm to vibrate. The electronics in the microphone uses this vibration to translate the soundwaves into audio.

Interesting Facts About Soundwaves

  • A person’s eardrums work basically the same as a microphone because when soundwaves create pressure around eardrums, they vibrate while allowing the brain to interpret those vibrations as audible sound.
  • Not all sounds are the same as they contain certain features such as loudness and pitch. The study of these features would later define what we know as music.
  • Sound pitch produces high and low Frequencies, which move their surrounding air back and forth. The more vibration the frequencies are creating, the higher the pitch of the sound and the lesser the vibration means a lower pitch of sound.
  • Humans hear sound best when soundwaves vibrate between 20 per second on low frequencies and 20,000 per second on the high frequencies.
  • Many buildings around the world today use devices that emit high-pitched noises that cannot be heard by people over the age of 25. These devices work to annoy teenagers and turn them away from loitering around the buildings.
  • There are sounds that are too high and too low for humans to hear. These sounds are referred to as Ultrasonic and Infrasonic.
  • Elephants have the ability to communicate with each other over long distances. This ability is the use of Infrasonic soundwave frequencies.
  • Elephants can communicate with each other over the span of several kilometers away from each other.

Why do humans tend to become deaf as they get older?

As humans age, they lose specific cells that work to detect sound. This results in the eardrums losing the ability to detect higher pitched soundwaves.

Pitch perception

Why are humans unable to hear dog whistles? 

Dog whistles create higher soundwaves with frequencies that humans cannot hear. These frequencies are known as Ultrasonic frequencies.

How is sound measured?

The measurement of sound is measured through units known as Decibels.

Why do ambulances sound louder as they approach?

Ambulances continuously emit soundwaves at a certain frequency through a siren. As the ambulance approaches you, the siren creates more soundwaves that are higher in pitch. The pitch of these soundwaves will decrease as the ambulance moves away from you and this occurrence is known as the Doppler Effect.