[thedoc (OP)]

Paul Anderson  asked the Naked Scientists:
   
Dear Chris and team,

A large dog barks once and it thinks it's the boss. A small dog yap yap yaps.

Is this genetics and could we engineer a big dog to yap and a small dog to bark once.

Could this technology be transferred to humans

Regards

Hen pecked husband

What do you think?

[chris]

This is to do with the way sound resonates and it's the same reason that children, and women, have higher pitched voices than adult men, and why helium makes your voice "sound" higher.

The vocal cords in the neck open and close to allow puffs of air into the mouth. These set up vibrations in the oral cavity and the bones of skull, which are transmitted to the outside world as compression waves that we experience as sound.

The "size" of the resonant cavity determines which frequencies resonate - and hence are relatively amplified - the most.

A big dog has a longer vocal tract and mouth than a small dog. This means that lower pitches will be relatively more amplified in the bigger dog's mouth compared with the smaller dog. Hence the "bark" will contain a relatively stronger representation of the lower frequencies  in the big dog, making it's bark sound more menacing!

It's the same in humans.

This naked science scrapbook episode explains the concept, including why helium has the effect that it does on the sound of your voice.