Mireu-vos i escolteu-vos aquests vídeos. Ens serviran per fer la següent prova a classe.

[youtube]https://www.youtube.com/watch?v=EDtK7xUIDxk[/youtube]

[youtube]https://www.youtube.com/watch?v=8D3c23uM3Qk[/youtube]

[youtube]https://www.youtube.com/watch?v=pdBnNzQz67A[/youtube]

[youtube]https://www.youtube.com/watch?v=6pN7eNSFXEY[/youtube]