For optimum performance the sonic horn manufactured by Primasonics® is exponential in shape, in other words it is designed in the shape of a 'bell' section. The reason for this shape is quite simple; the acoustic sound wave frequencies produced by each of our six selected frequency models are extremely pure in tone and powerful in performance due to this design. To understand better the need for the exponential, or bell shape of the sonic horn, a short interesting history of the bell may be helpful.
Firstly the definition of the bell as defined in the Encyclopaedia Britannica - "a special hollow vessel usually of metal, but sometimes of horn, wood, glass, or clay, struck near the rim by an interior clapper or exterior hammer or mallet to produce a pure ringing tone. Bells may be categorized as idiophones, instruments sounding by the vibration of resonant solid material, and more broadly as percussion instruments."
The early purpose of bells were to create clear power frequency tones which would travel long distances and therefore the exponential shape became established as the only way that all these goals could be met. For sonic horns, now referred to in industrial terms as acoustic cleaners, the important part in this definition is the vibration of resonant solid material, the bell shape resonates sound far more effectively.
The bell is primarily a musical instrument, designed to be used as part of a musical piece, or rung to invite parishioners near and far to their local Sunday service and as well as this the bell has been used to warn of impending danger.
The most famous bell in the United Kingdom is Big Ben and is housed in the tower below on the Houses of Parliament. Big Ben is 9'-0"/2.74m diameter, 7'-6"/2.3 high, and weighing in at 13 tons 10 cwts 3 qtrs 15lbs (13,760 Kg).
On the stroke of midnight every New Year's Eve people wait patiently to hear Big Ben chime in the New Year.
Pictured left is the Westminster Parliament Building and below right is the actual bell 'insitu'.
This bell has been consistently emitting true frequency tones across London since 31st May 1859, when the bells of the Great Clock of Westminster rang across London for the first time.
It is perhaps in the church where the bell is most recognisable. They have been used here for centuries to announce the beginning of the services that take place.
On a Sunday morning in villages all over the UK, bells can be heard ringing, the pure sound frequencies drifting through the air bringing the unmistakeable sound of the bell to the local people over a wide area.
Another famous bell is the Liberty bell. First chiming out true tones of frequency from the tower of Independence Hall it summoned the local citizens to be present for the first public reading of the Declaration of Independence by Colonel John Nixon on the 8th July 1776.
In actuality, bells have been used since more or less the beginning of civilisation. Amongst other things bells were used to frighten away unwanted and evil spirits and change the weather. By the time of the Middle Ages, the understanding of the mechanics of the bell improved, they were better crafted than their crude ancestor bells and even given their own towers.
The bell pictured is a Meneely made bell. The Meneely Company were the main manufactures of the bell in 19th and 20th century USA.
It is important to be aware that the shape of the bell has remained constant for centuries and centuries. This is because this shape, the exponential shape, is ideal for obtaining maximum acoustic power over long distances and at pure selected frequencies. Primasonics® utilised this bell shape and the bells ability to offer such clear tones at pre-selected wavelengths and at maximum power in the design of all their special range of acoustic cleaners. All our acoustic horn designs have pure fundamental frequencies of between 350 Hz and 60 Hz.
In the diagram below is shown the Primasonics® exponential sonic horn bell section on the left. Compare this with the cheaper, less effective conical bell section on the right. We would never use this straight conical design as we believe it to be detrimental to achieving both pure selected sound frequencies and also in utilising the maximum power of the particular Primasonics® Acoustic Cleaner.
To summarize, the correct design of the bell sections are critical. The history of the bell has proved that the exponential bell shape is the only true spare.
Thus the exponential shape of the bell sections in Primasonics® Acoustic Cleaners or Sonic Horns is vital in order to achieve both pure, powerful selected frequency tones and to cover a much larger area. Primasonics® Design Engineers have learned a powerful lesson from history which is now transposed into providing the best range of sonic horns available.
