Category: Sound

Ultrasound Scanning

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The ultrasound source produce vibrations at periodic intervals, causing the surrounding tissue particles to be disturbed, and also vibrates in a direction parallel to the direction of the sound waves.

As the tissue particles nearest to the ultrasound source vibrates due to the disturbance from the sound source, they will collide against neighbouring particles, transferring the vibrations from one particle to the next, producing alternate regions of compressions and rarefactions, transmitting the sound waves through the tissues, until the waves eventually reach the fetus, and reflect off the fetus body back to the receiver.

Movement of air particles in sound waves

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A sound wave in air is illustrated below.

Points A, B, C and D are all the centers of regions of compression in the sound wave.
Describe what happens as one complete sound wave moves past a point.

The particles in the air are disturbed by the sound waves and vibrates to and fro, in a direction parallel to the direction of the sound waves.
An air particle in the sound wave will vibrate from its rest position to the left, until it reaches its maximum displacement to the left, then vibrate towards the right, move past its rest position, until it reaches its maximum displacement to the right. Then it vibrates to the left, until it returns back to its original rest position to complete one wave motion of the sound wave.

Why does an echo fill an empty room, but not one that is fully furnished?

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In an empty room, the hard and solid walls, floors and ceilings act as good reflectors of sound, so the sound waves reflect repeatedly off these surfaces, creating echo.

In a fully furnished room, there are usually soft, hollow surfaces, like the fabric sofa; the thick curtains; the wardrobe, etc, that act as good absorbers of sound. This reduces the effect of echo.

How is sound transmitted through a medium?

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When the source of a sound wave vibrates, the surrounding particles are disturbed and vibrates in a direction parallel to the direction of the sound waves.

The vibrations are passed on from one particle to the next in a series of alternate regions of compressions and rarefactions, transmitting the sound waves through the medium.