As George Constantinesco pointed out in one of his papers, [10] perhaps it was Montgolfier who in 1797 invented the first sonic resonance machine, the hydraulic ram, although he was unaware that it would be classified as such more than 100 years later. The automatic action of the ram is due to the inertia forces of the water in the main supply pipeline. When the flow is suddenly stopped, the energy stored in the water cannot disappear and it causes water to rise in the delivery pipe to a higher level than its origin. In fact the hydraulic ram applied the principle of the conservation of energy. As early as 1864 the ram was showing efficiencies as high as 82%, better than any modern combination of engine and pump and comparable with the best turbines and centrifugal pumps.

As sonic energy is transmitted by periodic impulses an obvious application for it is in the operation of hammers of all kinds like rock drills and machines for riveting, chipping, crushing, piercing and for presses requiring rapid action. George Constantinesco applied sonic energy in this way to his rock drill as long ago as 1913 and to his synchronising gear for machine guns with devastating effect during World War I. The significance of these inventions in relation to drilling was soon recognized by engineers in the mining industry. The Romanians were first in the field with applications of sonics to deep drilling in the oil industry. They had taken note of George's encouragement and lectures during his visits to Romania and a Romanian translation of his book on The Theory of Sonics published in 1920.

During the 1930s the engineer Dr Ion Basgan was the first to introduce sonic vibrations in the drill pipe string of a conventional rotary drilling rig. The sonic currents caused the steel pipe string to oscillate up and down and thus to produce powerful blows on the bottom of the borehole through the rotating drill bit. This enabled the depth and speed of drilling to be greatly increased. It also enabled the drill to bore a truly vertical hole without distortion, which was not always possible with the old method. For example, at the Moreni oil fields in Romania in 1938 a bore hole was drilled 1,915 metres (6,300 feet) deep in 30 days by this method. Dr Basgan was granted patents on this technique in Romania and in the U.S.A. In 1933 he wrote a paper and in 1934 [11] published a book on the subject for which George Constantinesco wrote the Preface. The paper was presented in London at the first World Petroleum Congress in 1933 and was then published in 1935 in Moscow and Baku, under the title, 'The Foundations of Scientific Modern Drilling Methods'. Apart from the mining industry, small sonomechanical rotary hammer drills are now taken for granted as essential equipment in workshops, the building trade and private houses. They have greatly eased and speeded up the drilling process, particularly in rocks and masonry.

The frequency of sonic impulses for drilling can vary from only a few to more than 20,000 pulses per second which is in the ultrasonic range. The term "ultrasonic" was generally adopted after 1935 to replace "supersonic", which has since been confined to describing the speed of travel of objects in the air in excess of the speed of sound for example supersonic aircraft. The application of ultrasonics for deep drilling in the mining industry was developed largely in the USA, but from initial results obtained in the early 1960s, George concluded that the ultrasonic method would not be as efficient as the medium frequency sonic system originated in Romania.

Sonic pumps can be used to extract underground water or oil. These pumps dispense with cylinders, pistons, and rods. They consist of a steel tube inserted below the level of the liquid to be extracted, which is made to oscillate up and down by a sonic generator. At a series of junctions of the tube there are ball valves which open and close at the frequency of the vibrations imposed and this causes the liquid to move up the pipe. Numerous patents on the system have been taken out in the USA, Great Britain and Romania. Early tests showed the system could work satisfactorily to a depth of 6,000 feet or more. In one test a flow of six tons per day was obtained with a tube two and a half inches in diameter vibrating at 20 cycles per second and with half an inch motion up and down.

Sonic pumps also produce favourable conditions for the secondary recovery of the oil. This appears to be due to the vibratory action of the sonic waves diffused into the strata surrounding the tubing at the bottom of the hole and also to the heating or thermosonic effect which increases the fluidity of the oil. Thus, the use of sonic pumps provides a cheaper alternative to the costly method of flushing with vast amounts of water. The thermosonic effect also prevents paraffin wax deposits forming inside oil extraction tubes which would otherwise take place due to crystallization of the wax with failing temperatures. The sonic vibrations not only prevent deposits forming but also dissolve existing deposits back into the liquid. This whole process lasts only 30 to 50 minutes and may be repeated every three days, instead of the old system, which entailed pulling out the whole pipe-string for cleaning every four to five days.

It is strange that in spite of the major impact of sonics on the oil industry, it is seldom mentioned in modern literature that it was George Constantinesco who first developed the Theory of Sonics on which those applications are based. George complained about this himself in his paper on sonics read at the Society of Engineers in June 1959,  [2], and Charles Jaeger reminded the delegates of this fact at the International Congress on Hydrology in London in 1963.

Through his experiments and inventions, George demonstrated the generation and application of powerful waves of sonic energy in the medium frequency bands through air, liquids or underground rocks but he had also succeeded in generating ultrasonic frequencies up to 100,000 cycles per second in the early days of World War I, in which he had also noted a thermosonic effect. He reported upon these experiments in a lecture to the Romanian Academy of Science in 1919 and predicted many of the applications of ultrasonics in use today in industry and medicine. Many of the applications which have developed in recent years are in the field of applied acoustics and electroacoustics in which the amount of sonic power transmitted is small. It is however of interest that ultrasonics are now used extensively in industry for a variety of applications such as the machining and non-destructive testing of metals, the detection of flaws in materials and manufactured articles, the ageing of fermented beverages and the conversion and storage of electrical signals in radar and computers.

Ultrasonic vibrations generated by electroacoustic methods prevent the formation of large crystals and may be used in metallurgy, for example in refining aluminium and magnesium castings. On the other hand George found it was possible to obtain satisfactory results by using sonic currents of only a few hundred cycles per second but of much higher energy than obtainable by electroacoustic methods. In another experiment however he was able to produce ultrasonic waves cheaply with generators of the kind he had developed at West Drayton for use with ships and used them to precipitate particles of ashes from flue gases, acids from fog and carbon black from methane gas.

Sonic vibrations can also be used in medicine, with both low or high frequencies, for example in ultrasonic scanning, neurosurgery and therapy. The vibrations are not dangerous, like X-rays and can be beneficial. The sonic currents penetrate deeply through the tissues without danger of burning or shock. In therapy they are believed to have a beneficial effect by their deep seated massaging action and warming due to the thermosonic effect of the radiation.

At the other extreme, very low frequencies, or 'infrasonic' currents can be generated by slow moving machines such as water turbines, or windmills to work forging hammers, presses, pumps or machine tools. Applied to railway signalling, the passing of a rail coach or locomotive could operate a sonic generator fixed to the track to open and shut distant signals, road barriers or fog signals. George was granted a British patent on this idea in 1916, being a typical example of the application of percussive waves through liquid in a pipe to actuate a receiver or motor at a distance from the generator. The pulses produced by the generator are akin to sound waves and travel along the delivery pipe at the speed of sound applicable to the medium employed. This idea is a true hydrosonic application, the same as used for rock drills, the machine gun synchronising gear and Diesel engine fuel injection equipment, but of lower frequency.

The use of medium frequency bands of sonic energy in industry for percussive purposes and both ultrasonics and medium frequencies in metallurgy and medicine have been well researched and applied. However, the other major use of medium frequency sonic energy for the operation of rotary machines, comprising constant speed step-up and step-down and infinitely variable transmissions, appears to have been neglected! George Constantinesco was the path-finder in this respect with his inventions of hydrosonic and sonomechanical transmissions during the first quarter of this century. Sixty years later, which is not an unusual time lag for an invention to be forgotten and resurrected due to changing circumstances and needs, there is renewed interest in the possibilities of applying these kinds of transmission to both static machinery and vehicles of transport on land and water.