Ultrasonic waves have many incredible applications across a wide variety of industries, ranging from medical science to manufacturing. Not least among these is ultrasonic cleaning, which uses ultrasonic sound waves traveling through liquid to produce cavitation bubbles that clean more thoroughly than solvents and scrubbing alone.

Ultrasonic waves can’t be heard by humans, though some animals, such as bats, can hear them. Their effects on materials and their abilities may look like magic, but they’re pure science.

Unlike normal ways of making sound, which often involve striking a surface, ultrasound is made using electrical equipment that vibrates with an extremely high frequency.

Crystals of materials such as quartz vibrate very fast when electricity is passed through them—an effect called “piezoelectricity.” As they vibrate, they manipulate the air around them and the fluids they come in contact with, producing ultrasound waves. Devices that produce ultrasound waves using piezoelectricity are known as piezoelectric transducers.

Ultrasonic cleaning requires high-frequency waves

The type of ultrasonic waves used for cleaning are high frequency, usually measuring between 20,000 Hz (20 kHz or 20,000 cycles per second) and 400,000 Hz (400 kHz or 400,000 cycles per second), which is much higher and more powerful than ultrasonic waves used for medical imaging or manufactured products flaw detection.

The reason for this high frequency is when these powerful ultrasonic waves pass through liquid and strike against the surface of an object, they produce cavitation bubbles, which are bubbles that collapse with high energy release. Millions of these tiny bubbles exploding per second have the combined effect of thoroughly cleaning objects. To find out more about how this works to clean even the toughest grime from parts, visit Omegasonics’ Ultrasonic Cleaning 101 page.

The power of piezoelectric transducers

When ultrasound is purposed for cleaning things, a high-frequency alternating electricity supply sends power to piezoelectric transducers. If mechanical pressure is applied to one pair of opposite faces of certain crystals like quartz, equal and opposite electrical charges appear across its other faces. This effect is called the piezoelectric effect. The converse of piezoelectric effect is also true, in that if an electric field is applied to one pair of faces, the corresponding changes in the dimensions of the other pair of faces of the crystal are produced. This effect is known as inverse piezoelectric effect.

As the piezoelectric transducers vibrate at ultrasonic frequencies, they send their vibrations to a thin, quartz glass plate. This plate transmits the ultrasonic waves into a basin filled with fluid into which the objects are placed to be cleaned.

It should be noted that ultrasound waves can also be produced using magnetism instead of electricity. Just as piezoelectric crystals produce ultrasound waves in response to electricity, so there are other crystals that make ultrasound in response to magnetism. These are called magnetostrictive crystals and the transducers that use them are called magnetostrictive transducers. (The magnetive effect is known as magnetostriction.)

Ultrasonic waves are an often-overlooked application of electrical and acoustic science which have a great effect in the manufacturing industry, among many other industries. To find out more, call Omegasonics at 888-989-5560 or email us at omegasonics@omegasonics.com