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07-03-2014 Post does not mapped to Knowledge Tree
Romy the Cat

Boston, MA
Posts 10,052
Joined on 05-28-2004

Post #: 1
Post ID: 21076
Reply to: 21076
NASA Reverberant Acoustic Test Facility.
I have no idea what that all about but it is nice to know that my taxes goes for somebody building horns.

"The Reverberant Acoustic Test Facilit (RATF) chamber is located within the Vibroacoustic Highbay, taking advantage of the 1.8 m (6 ft) thick surrounding concrete walls to help attenuate sound migration through the SPF. The highbay also serves as redundant protection from the RATF nitrogen atmosphere during operation. The RATF is a 2,860 m3 (101,189 ft3) reverberant acoustic chamber capable of achieving an empty-chamber acoustic overall sound pressure level (OASPL) of 163 dB. The facility structure is designed for a future upgrade to 166 dB OASPL, including areas in the horn room wall which have been left blank for future installation of additional modulators/horns. The RATF includes various supporting sub-systems including gaseous nitrogen generation system, horn room with acoustic modulators and horns, acoustic control system, and hydraulic supply system. Test articles are mounted onto elevated customer-provided mounting fixtures for testing. The chamber has been constructed with load-bearing wall attachments for future installation of a 5-ton interior bridge crane. The chamber can be operated as a Class 100,000 clean room once the access doors are closed and the facility is cleaned. The combinations of servo-hydraulic and electro-pneumatic noise modulators utilize gaseous nitrogen capable of producing a tailored wide-range of acoustic spectrums in the frequency range from 25 to 10,000 Hz. The RATF chamber internal dimensions are 11.4 m (37.5 ft) wide by 14.5 m (47.5 ft) deep by 17.4 m (57 ft) high.

A maximum of 19 control microphones can be placed around the test article for closed-loop control using the Acoustic Control System (ACS). The ACS, control microphones, or other response instrumentation (accelerometers, microphones) may be input into the Analog Abort System (AAS) to provide automatic shutdown capability. Each of twenty-three (23) servo-hydraulic acoustic modulators is coupled with individual horns of six different cut-off frequencies. Each of thirteen (13) electro-pneumatic acoustic modulators is coupled with individual horns of one cut-off frequency. This combination of modulators and horns provides for an extremely variable and tailored acoustic spectrum. Threaded inserts are located in the floor for attachment of test article mounting fixtures.

The East side of the chamber has a large rolling door and hinged door to provide access to the chamber up to 10.5 m (34.5 ft) in width. A 5.5 m (18 ft) wide by 4.2 m (14 ft) high door is located on the West side of the chamber for loading equipment when the vacuum chamber is occupied.
The Vibroacoustic Highbay is secured and support systems (hydraulics, compressed air, liquid nitrogen, gaseous nitrogen, HVAC systems, and video systems) are setup and energized. A watchdog Facility Control System (FCS) monitors these sub-systems and ensures that all permissives and interlocks are verified. The acoustic chamber is filled with a predetermined level of gaseous nitrogen. The FCS verifies that a matching modulator selection file agrees with the ACS and subsequently provides a Run Permit to the ACS. The ACS performs a self-check and the operator initiates testing using the tailored choice of modulators/horns. The nitrogen generation system automatically vaporizes liquid nitrogen into gaseous nitrogen as required up to 1,981 standard cubic meters per minute (70,000 scfm). At the conclusion of testing, fresh air is force-ventilated into the chamber via the HVAC system to purge the chamber of nitrogen for safe entry. Temperature, humidity and oxygen monitors are located in the chamber and highbay."



"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
07-04-2014 Post does not mapped to Knowledge Tree

Posts 440
Joined on 07-05-2012

Post #: 2
Post ID: 21077
Reply to: 21076
The Europeans only got 155dB
The main parameters of the LEAF are listed below:

Frequency Range 25Hz - 10KHz
Noise field homogeneity +/- 2dB
Control accuracy in 1/3 octave band:
• 25Hz - 40Hz
• 50Hz - 63Hz
• 80Hz - 800Hz
• 1000Hz - 2.5kHz
+/- 2dB
+/- 1dB
+/- 0.5dB
+/- 2dB
Chamber Dimensions 11 x 9 x 16.4m


Whenever I feel blue, I start breathing again.
07-07-2014 Post does not mapped to Knowledge Tree
Southern California
Posts 9
Joined on 10-23-2011

Post #: 3
Post ID: 21078
Reply to: 21076
Very curious...indeed.

Very best regards,
08-08-2014 Post does not mapped to Knowledge Tree
Posts 4
Joined on 12-29-2013

Post #: 4
Post ID: 21161
Reply to: 21078
A Sound System That's Loud Enough To Kill

This looks a bit like a giant ear canal, but in a way, it's the opposite. It's the largest horn in the most powerful sound system in Europe. The system's maximum output, according to the European Space Agency, would kill any human exposed to it. 

The horn is part of the European Space Agency's Large European Acoustic Facility in Noordwijk, the Netherlands. The facility blasts sound at spacecraft components to test whether they're able to withstand the intense noise of launch. There are four horns, to create sounds in a range of frequencies. ESA engineers send nitrogen gas through the horns to create noise of more than 154 decibels.

Whether that's enough to literally kill is unclear. (There are so many variables. Did the agency mean "kill you on contact" or "kill you if you're sealed inside the facility for a while"?) At the very least, it would cause some serious damage. The eardrums rupture at around 150 decibels. The lungs rupture at around 200 decibels.

For safety, the facility has half-meter-thick walls made of steel-reinforced concrete coated inside with epoxy resin, which reflects noise into the chamber. It also won't operate unless all of its doors are closed.

  leaf horn.jpg


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