L'attirail

Acoustic seals are a form of door seal that are designed primarily to prevent the passage of noise into or out of a room. They work by sealing off air gaps so that the noise is unable to pass through any open gaps. One of the beneficial side effects of having acoustic seals installed in your home is that they also prevent the passage of dirt, dust, and even smoke through the same gaps. Acoustic seals can be used in residential, commercial, and retail properties to great effect.

Acoustic seals are a form of door seal that are designed primarily to prevent the passage of noise into or out of a room. They work by sealing off air gaps so that the noise is unable to pass through any open gaps. One of the beneficial side effects of having acoustic seals installed in your home is that they also prevent the passage of dirt, dust, and even smoke through the same gaps. Acoustic seals can be used in residential, commercial, and retail properties to great effect.

Sound Escape

Sound is most commonly lost through the door seal around the top, bottom, and sides of a door. Even the slightest gap that is left allows sound to travel from one area to another and without adequate sealing this will continue to be the case. No amount of soundproofing in the room, under the floors, or anywhere else around the area will fully prevent the escape or entry of noise.  Read more...

History of the acoustic metamaterials

Acoustic metamaterials actually began with electromagnetic metamaterials, and the construction of materials to control electromagnetic radiation before that.

Maxwell’s equations which predicted the existence of electromagnetic radiation propagating at the speed of light, by James Clerk Maxwell, were made public in 1865. In 1888 Hertz had demonstrated generation of electromagnetic waves, and showed that their properties were similar to those of light.

Before the start of the twentieth century, many of the concepts now familiar in microwaves had been developed. The list includes the cylindrical parabolic reflector, dielectric lens, microwave absorbers, the cavity radiator, the radiating iris and the pyramidal electromagnetic horn. Round square and rectangular waveguides were used, with experimental development anticipating by several years Rayleigh’s 1896 theoretical solution for waveguide modes.

Many microwave components in use were “quasi-optical”. Oliver Lodge first introduced the term – quasi-optical. A treatise on microwave optics was published by Righi in 1897.

Hertz had used a wavelength of 66 cm; other post-Hertzian pre-1900 experimenters used wavelengths well into the short cm-wave region, with Bose in Calcutta and Lebedew in Moscow independently performing experiments at wavelengths as short as 5 and 6 milimeters.

Jagadish Chandra Bose used waveguides, horn antennas, dielectric lenses, various polarizers and even semiconductors at frequencies as high as 60 GHz. In 1898 he tried to develop and did experiments with “constructed” twisted elements.  Read more...

There is a story that the first European college jazz course began in Frankfurt, Germany, in the early nineteen thirties, but was promptly closed down after Hitler seized power in January 1933!

The story, though difficult to confirm, has the ring of truth. Had Jazz Education been available so early in the history of jazz (the first jazz recordings appeared in 1917), the Jewish and Negro elements present in the music would have guaranteed the disapproval of the Nazis.

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Alas, they were not alone. Even Lord Reith’s BBC forbade the broadcasting of dance music on Sundays during the 1930′s.

Jazz has been the recipient of hostility and cultural philistinism throughout its eighty years.

Now it is pleasing to report to a steady post-war growth in opportunities for serious study of jazz at college level, leading to a current boom in provision.

In the nineteen forties America led the way, the most famous pioneer being the Berklee College of Music in Boston. Berklee still thrives today but has tough competition from numerous excellent courses, both in America and Europe. Jazz came from America and uses American popular song; so the language of jazz is English. The language of jazz education, from the blackboard to the bandstand (and vice versa) is also English. Couple with that fact the emergence of European Jazz as a distinctive genre, and study in Britain is increasingly seen as first choice for the international student wishing to combine the polishing of his or her English Language skills with the sharpening of jazz abilities.  Read more...

History and Design

An acoustic cleaner consists of 2 parts.

The wave generator which takes the compressed air and applies it to a diaphragm. The wave generator is usually made from solid machined stainless steel. The diaphragm within the generator is the only moving part within an acoustic cleaner and there is no danger of sparking.The diaphragm is usually manufactured from special aerospace grade titanium to ensure performance and longevity.

The bell, which is usually made from spun 316 grade stainless steel. The bell is a resonance section or amplifier and it will tune and direct the sound waves.

An acoustic cleaner is powered by compressed air with an operating range of between 4.8 to 6.2 bars or 70 to 90 psi. The resultant sound pressure level will be around 150 dB.

The overall length of the acoustic cleaner will range from between 430 mm to over 3 metres long.

There are generally 4 ways to control the operation of an acoustic cleaner.

The most common is by a simple timer.

SCADA.

PLC (programmable logic controller).

Manually by Ball valve.

An acoustic cleaner will typically sound for 10 seconds and then wait for a further 500 seconds before sounding again.

This ratio for on/off is approximately proportional to the working life of the diaphragm. Provided the operating environment is between 40 and 100 C a diaphragm should last between 3 and 5 years. The wave generator and the bell have a much longer life span and will often outlast the environment in which they operate.  Read more...