Sound Production

Sound can be produced in a variety of ways

Humans

The larynx

The larynx is a complex structure located at the front of the throat - neck.


The larynx is part of the trachea a passageway surrounded by rings of cartilage which is connected to the oral cavity and the lungs. The major function of the larynx is to produce sound. Sound is produced through many different structures which make up the larynx. The larynx is made up of nine different cartilages. The vocal chords are connected to some of these cartilages and extend across the tracheal opening. These vocal chords are made up of elastic fibres. As air rushes up from the lungs the vocal chords vibrate which results in the production of sound. The vocal chords and larynx surround a narrow opening of the trachea called the glottis.


Speech involves the passage of air passing through the glottis. The pitch of the sound is altered by the length and tension of the vocal chords as well as the degree of the opening of the glottis. High pitched noises are due to the following structural characteristics; tense short vocal chords, vocal chords that vibrate at a fast rate and the glottis forming a narrow passage for air to pass through. Low pitched noises are due to the opposite; relaxed long vocal chords that vibrate at a slow rate with the glottis forming a large passage for air to pass through.


Louder noises are produced by the amount of air being forced through the and across the vocal chords.


The other structures associated with the production of sound in humans are:

  • The tongue
  • soft palate
  • hard palate

Frogs, Reptiles and Birds

Frogs

  • Male frogs produce a croaking noise for various forms of communication, for reproduction or the marking or territory by various males.
  • The croak is generated by vocal sacs and their mouth cavity.
  • Sound is produced by forcing air out of the lungs across the vocal chords causing them to vibrate. Muscles in the surrounding trunk area contract to expel the large amounts of air to produce a croaking noise.
  • Croaking is species – specific meaning that each individual species produces a croak at a different frequency compared to that of different male frogs
Bull Frog Call

Reptiles

  • Reptiles produce sound for various forms of communication such as for reproduction or warning off other predators.

  • Sound is produced similar to that of the frog. Depending on the size and shape of the vocal chords air is expelled from the lungs to produce a sound. For example a snake will “hiss” to scare off predators, a gecko will “chirp” to call other geckos and a crocodile can produce a variety of sounds including “roar,” “hiss,” and “bark.”
Tokay Gecko mating call

Birds

  • Birds produce various calls or songs to warn others of predators or for calling a mate.
  • To produce these calls birds have a special structure known as a syrinx.
  • The syrinx is generally located at the base of the trachea.
  • The rings of cartilage the surround the bronchi and trachea are modified in the syrinx. They have partially become muscular in nature which results in the “bird call.”
  • Different vibrations of the membranes and the amount of air expelled causes different sounds produced by different birds.
Amazing! Bird sounds from the lyre bird - David Attenborough - BBC wildlife