How do sound box of violin and other instrument amplify the sound wave?

Answer 1

The sound produced from a violin originates from the vibrations of its strings. When the bow is swept across a string, it is forced into vibration. Since the string is fixed at both ends, a standing wave is produced with nodes at the fixed ends, in the form of a fundamental note. This fundamental note determines the pitch of the vibration. At the same time, many other harmonics are formed along the vibrating string, but their differing pitches do not have much effect on the fundamental pitch – they only add a richness and complexity to the timbre, giving the violin its unique sound. As the string vibrates, compressions and rarefactions of air molecules around it are produced, which transmit the sound energy to our ears. But the string alone is too thin to produce much sound. To amplify the sound produced, the vibration of the string is transmitted to the body through the bridge and the soundpost, forcing the whole violin into vibration. Since the body has much greater area in contact with air than the string alone, a much stronger sound wave is produced. Furthermore, the wood of the violin is designed to have many resonance frequencies, so the wood can be set into resonance from almost any pitch of the vibrating strings. The soundholes and the air inside the hollow violin also add to the resonance, amplifying the sounds produced.


SOUND BOX'S ROLE:
the sound box is so constructed that the column of the air inside it,has a natural frequency same as that of the strings streched on it,so tha twhen they r put inot vibrations,the air column inside is set into resonation and it reinforces the sound

Answer 2

The hollow body of the violin is the sound box, and when the strings vibrate as they're played, the vibration is sort of transmitted so that the air in the sound box vibrates, making the sound louder. There're these f/s shaped holes at the sides of the violin that the sound comes out from.

The back plate's also supposed to be resonant and I think the sound's transmitted there by the sound post under the bridge or something.

(Sorry can't guarantee the accuracy of the technical terms, I just play it.)

Answer 3

They resonate.