By George Hutchinson, Vice President Engineering
Ultrasound is sound with a frequency greater than the upper limit of human hearing, this being approximately 20 kilohertz (20,000 hertz). Ultrasound is generated by the Sonic Solutions® transducer that converts low power electrical energy into a high frequency acoustical sound wave. These sounds are thus a form of transmitted mechanical energy projected through a body of water. The device actually operates in the same general frequency range as a sonar device or a boat depth/fish finder.
There are a broad range of ultrasonic applications. They range from healing technologies to weapons used in the military. The medical applications can range from low intensity to high intensity. The industrial industry uses ultrasound to find flaws in materials. Sonochemistry is used to enhance chemical reactions. High powered ultrasonic devices can lyse (break apart) cells for oil extraction techniques to harvest algae oil through a phenomenon called cavitation.
When you hear of harm being caused by ultrasound it is typically due to induced cavitation
(micro-bubble boiling) that can cause cell damage. This requires a very high power output. The Sonic Solutions® devices while approaching the threshold of cavitation do not operate within this ultrasonic intensity region.
High intensity focused ultrasound applications include breaking up kidney stones and dental hygiene teeth cleaning process. The ultrasound imaging used on an unborn fetus utilizes 2000 watts of power. Cleaning jewelry or surgical instruments are done at the 20 – 40 Kilohertz range. Benign and malignant tumors are treated via a process known as Focused Ultrasound Surgery which generally use lower frequencies than medical diagnostic ultrasound (from 250 - 2000 kHz), but significantly higher time averaged intensities. The treatment is often guided by MRI, as in Magnetic Resonance guided Focused Ultrasound.
Everything on the earth vibrates and has a resonance frequency which can be affected by sound waves. At the same time each living organism on earth has a “critical” resonance frequency which when subject to that particular sound wave can do damage to it. For example, Ella Fitzgerald can break a crystal glass by singing at its critical resonance frequency.
In sound applications, a resonance frequency is a natural frequency of vibration determined by the physical parameters of the vibrating object. Some of the implications of resonant frequencies are:
It is easy to get an object to vibrate at its resonant frequencies, but hard to get it to vibrate at other frequencies.
Most vibrating objects have multiple resonant frequencies. For example: an out of balance car tire.
To cause a harmful vibrational effect, a combination of the resonance frequency and sufficient power must be applied. For example, one can draw an analogy to the electromagnetic waves in a microwave that match the same natural frequency of water. With humans having the majority of their body makeup as water – microwaves will harm humans due to our bodies matching the resonance frequency of water. If the frequency generated by sound or electromagnetic waves does not match a critical frequency in a living thing – it has little to no effect on it. For example radio waves pass through human bodies and do us no harm because we do not synchronize with that frequency. Plastic in a microwave oven does not heat up because its natural frequency is different than water.
The Sonic Solutions® unit outputs multiple frequencies throughout a range to match the critical resonance frequency of green algae contractual vacuole cell walls and also blue-green gas vesicle walls – thus causing the walls in these organelles to break.
When an output frequency with sufficient power is close to that of an algae contractual vacuole, the vibrational force causes it to tear from the surrounding inner cell wall called the plasmalemma. The inner cell wall holds the fluid pressure inside the cell. The pressure is provided by the contractual vacuole. Without this simple attachment, the cell cannot grow and soon dies as fluid transfer is disrupted inside the cell.
In blue-green algae, the impact is much different. The hundreds of gas vesicles in each algae cell that are broken normally provide buoyancy allowing the cells to reach the surface to get sunlight. Without them they sink out of light and slowly die. The gas vesicles are not critical life function devices, such that the cells will continue to survive if nutrients and sunlight are sufficient. In most ponds and lakes, the sinking effect is enough to cause death due to lake of sunlight.
Since life forms and organisms of a higher order do not match the critical resonance frequency of an algae vacuole it has no affect on them. The 5 models of Sonic Solutions available address the size of the body of water by applying sufficient power of the sound wave to cover the desired area.
This technology since its beginnings nearly 15 years ago, has never recorded damage to higher order life forms. Likewise, the Sonic Solutions® devices operate at a frequency and intensity that is harmful to algae, yet at a power output level that does no harm to other life forms.