Report - - Pyestock Anechoic Facility - August 2017 | Industrial Sites | 28DaysLater.co.uk

Report - Pyestock Anechoic Facility - August 2017


Behind Closed Doors
Regular User
The last piece of Pye.

I’m sure everyone who visited Pyestock before it was demolished will remember the Anechoic Facility, that one last bit of the puzzle that couldn’t be visited. The blue-tailed building was still in use long after the demolition of the rest of the site, and is the only surviving part of Pyestock’s original host of facilities. This last part of the site has now also closed.

Visited with @SpiderMonkey and @darbians.


The National Gas Turbine Establishment.

For those who don’t know, NGTE Pyestock - The National Gas Turbine Establishment - was a huge industrial site in Fleet, Hampshire. The site was used to test jet engines during their development and could simulate the conditions of flight in huge wind tunnels. Large scale expansion took place throughout the 50s and 60s to facilitate the much larger jet engines being developed such as those used on Concorde. The site finally closed in 2000 due to a decline in jet engine development and the advent of computer aided simulations.

The Noise Test Facility

A lot of research into noise took place at NGTE over the years, and the first anechoic chamber was built in the early 1960s. The increasing demand for quieter aircraft stimulated the more research work, and as a result a larger test facility capable of undertaking large scale noise tests on a variety of gas turbine components opened in the 1970s.

The new facility consisted of two main laboratories, fully independent of each other. These were the Absorber Rig Facility and the Anechoic Chamber facility. The Absorber Rig Facility was the first to be completed and it came into service in the summer of 1972. The Anechoic Chamber Facility was commissioned just over one year later in early 1974.


The noise test facility in the 1970s before the blue inlets were installed​


The blue air intakes and associated fans were installed during a refit in the 1990s​

The plans below show the general layout of the building. The anechoic chamber is central with silenced air intakes to the left and the silenced exhaust duct and extraction fans to the right. The induced airflow passes through the anechoic chamber where the noise tests were conducted.


The Anechoic Facility has a 10,000 cubic metre chamber for noise testing in which the enclosed working volume has nearly zero noise reflection, thereby reproducing environmental conditions which can be compared to those in flight, and permits work to separately identify the source and direction of noise wave phenomena. The building is principally intended for the noise testing of jets, turbines and certain configurations of acoustically lined ducts.

Broadly, the facility consists of an acoustically lined main test chamber 85ft wide and 46ft high with an overall length of 88ft, but which is reduced to 52ft at the working section. The jet flow from the main noise source is projected towards an acoustically lined, flared duct 28ft diameter at inlet with a 20ft diameter throat, which acts as an exhaust inducer.


General view of the anechoic chamber with the exhaust duct to the left and working section to the right


View towards the exhaust duct showing fixed microphone towers





View from a hatch at the top of the working section, showing ceiling mounted crane​

Three observation galleries were positioned around the chamber. Each could be retracted to preserve the room's anechoic properties:


The most striking feature of the anechoic chamber itself is the sound reflecting wedges of which there are nearly 7,000 units covering the walls, ceiling and floor. Three individual wedges are mounted together on a base-frame to form each single unit 610mm square; these units are then arranged over the chamber surfaces so that each successive unit has its wedge peak edges at right angles to the neighbouring unit.


The working section was modified during refurbishment in the 1990s. A permanent nozzle was fitted through which high pressure air could be blown in using the blue external assembly shown in earlier pictures.



Inside the working section the area where jet engines would be positioned was replaced with a network of pipelines feeding the new nozzle.




Large air inlet pipe behind the nozzle


The rig room before the refit


The exhaust collector was responsible for transferring the jet engine exhaust gasses and induced air from the chamber to the exhaust silencing structure behind it. It is acoustically treated around its periphery, this lagging consists of heavy density rockwool 8in thick, faced with cotton sheeting and perforated galvanised mild steel sheet. The duct itself is prefabricated from 0.25in thick steel plate and has a total length of 35ft.


The exhaust collector


Selfie shows the scale of this huge hole in the wall


Behind the exhaust collector


Air and exhaust gasses then pass into the exhaust silencing structure. The main features of the structure, other than the exhaust collector are the acoustically slabbed walls of the concrete ducts which reverse the flowpath, two sets of silencing exit splitters, high and low frequency, and the ten exhaust extraction fans.


Low frequency splitters on the left, and one of the two sets of high frequency splitters on the right. The pole is a fixed microphone boom.


Another selfie showing scale​

The fan units themselves are double axial units having two counter-rotating six bladed fans in each pod, both with its own electric motor.


One of the two sets of five extract fans, plus one redundant space for an additional fan.


The new arrangement after the refit was particularly suited to testing ducts and propellers. One such item was found boxed up below the working section. This was possibly the last item to be tested at the site.


A separate building, houses the control and engineering service equipment. This building has three floors and the heavy service plant was originally installed on the lower floor with the service supplies fed to the rig room via an underground communication duct; the main control room is on the middle floor, while the upper floor houses the ancillary electronic equipment.


The control room and Fourier Analyser as originally fitted​

The control room was refitted with computerised equipment during the refurbishment in the 1990s. All that remains from the original control room is a single panel, the Plant Controller board.


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Camera Drowner
Regular User
Another cracker, brilliant report!
I was down this way the other day but assumed Pyestock was all long gone. Dammit.


Maglite size T-rex, It's time for urbex!
Regular User
Nice work, that looks awesome. Having never been I'd just assumed the whole place was gone, but evidently not.


Regular User
Wow, this is very nice. I expect it will get locked up now


28DL Regular User
Regular User
Wow, this is very nice. I expect it will get locked up now
If you take the old school approach to pyestock it will be perfectly fine. It's the ones who can't be bothered to get back out and get busted instead that will fuck it up. Or maybe the idiot who pulled a lever already has :banghead sorry :coat
Anyway great pics and it was great to get the final slice of pye with you.


Got Epic?
Regular User
Yeh this seems to have been doing the rounds for months now but a lot of stuff doesn't pop up on here for months anymore, if at all, which is a bit of a shame..? Still, good to see it in full, wish i had time to batter some of the recent epicness thats cropped up!

(Anyone else remember Aquilla? One of the first reports i ever read on Cornwell's site!)

professor frink

Reppin Bumbaclaat
28DL Full Member
You can't beat a bit of Pyestock :thumb
Millions of pounds spent on complex test rigs which could probably be replaced today by one modern laptop.
Need to move fast before it gets fooked.

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