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Occasional posts on subjects including field recording, London history and literature, other websites worth looking at, articles in the press, and news of sound-related events.

24 June 2017

Long in the tooth

THE FIRST proper field recording I made was in April 2008 and it featured the sounds of Petticoat Lane market on a Sunday morning. Since then I’ve tried to come up with a variety of ways both to guide the making of recordings and present them on webpages. I hope my efforts have given at least some pleasure to site visitors over the years.

The website is becoming a bit long in the tooth now, and needs to have its content management system upgraded if it’s to keep working. This will mean it going offline for around a week sometime soon while all the templates are rejigged. The audio players too will need a lot of attention to make them compatible with the ever-growing variety of tablets and smartphones.

Another long-hoped-for change will be a move from field recording to oral history interviewing. Seeking out and presenting the city’s sounds can be very enjoyable but subject to the law of diminishing returns, so that the site ends up like an obsessively detailed theatre set onto which no actors ever emerge. Time for a change of approach.

Interviews for the first oral history project begin in July this year so hopefully it shouldn’t be too long before you can start to see and hear the results.

16 January 2017

Against the wind: Rycote Cyclone windshields and a new baffle

A CONDENSER MICROPHONE has a diaphragm that’s open to the air, a backplate hidden out of view behind it, and a voltage across them. Sound waves impact on the diaphragm and make it move nearer to and further from the backplate, causing fluctuations in electrical capacitance.

In an ideal world sound waves alone would make the diaphragm move, but that’s not how it works out in real life. Sudden jolts, tapping the mic’s casing, and vibrations propagated along the cable can all produce unwelcome noises. So too can the wind and, more specifically, the turbulence in the air stream which batters away at the diaphragm. The solution is to absorb as much of that energy as possible before it can be transferred to the diaphragm, like the way a harbour breakwater is there to absorb the energy of the sea’s waves.

Any mic used outdoors needs some kind of protection from the wind. Furry windcovers are made for the mic pairs at the business ends of pocket-sized recorders. A larger mic can be mounted inside a mesh windshield equipped with a handle or stuck on the end of a boom pole: a standard arrangement for many professional field recordists.

I’m more of a hobbyist who’s become wedded to using omnidirectional mics in pairs. These can produce an appealing stereo image when used with some sort of acoustic baffle between them: this old blog post goes into more detail about that. One of the problems of this approach is that it’s not easy to protect the mics against wind because one side of them is up against your head or some head-substitute, like a wooden or closed-cell foam block.

A way around this presented itself when Rycote introduced their new Cyclone windshields. I noticed that they split lengthways into two and thought you could make an acoustic baffle out of a wooden block with one half of a windshield shell attached to each side, covering and protecting the mics under them. However, the Cyclone halves are asymmetric: the port side (relative to the mic facing forward) has the whole rear end-cap, and the starboard side has the larger front end-cap.

Rycote kindly agreed to supply me with two starboard sides, thus saving me the expense of buying a pair of complete windshields. I then set about making the baffle, starting with a wooden chopping board as the core, with most of the baffle’s volume comprised of balsa wood, given about six coats of varnish to toughen it up. This is what it looks like from the front.

The back shows (a) no great prizes for woodwork skills and (b) how the cables are carried beneath removable side blocks to exit at the rear. At its widest point the baffle is about one foot or 30cm across.

With the windshield covers removed, you can see how the mics are held in place with tool clips, and the covers are positioned with the help of metal pegs (cheap drill bits embedded and glued into the wood). Black sticky-backed foam makes for a more draught-tight surface for the edges of the Cyclone halve to come into contact with.

Tony at the Wire magazine asked if I wore it on my head, perhaps hoping for an amusing photo opportunity. No, it goes on top of a tripod. I mean, like, obviously! Here it is with some camo scrim wrapped round it at an RSPB nature reserve in Suffolk. Without the camo it looks maybe a bit alarming to birds, and several people have pointed out that it also resembles a big pair of stupendous breasts and, even though form strictly follows function, this is true. It’s not a bad thing in my view and, in fact, I’m proud to be doing my part to help redress the balance against countless consumer products which have a distinctly phallic appearance. But maybe sometimes modesty’s the better policy.

The tool clips allow a small degree of latitude in sliding the mics backwards and forwards. If they’re too far back, then the recording might suggest an acoustic hole-in-the-middle, with plenty of sound at each side but not much sense of anything happening directly in front. This seems to be happening with the first trial recordings I made in Suffolk.

The mics used on the baffle are Sennheiser MKH 8020s which have low self-noise, making them suitable for very quiet environments. Here’s a later attempt along the Thames estuary, with the mics moved forwards perhaps half an inch.

Neither of those recordings address the issue of wind, as the Suffolk one was made on quite a still day, and the Shornemead Fort one was made during blustery weather, but where the fort’s structure made an effective windbreak. The other day I saw that the weather forecast was predicting gusts of up to 37 miles per hour along the Thames estuary, so I went to Rainham to see how things would work out. It really was windy that day and only the baffle’s weight prevented the tripod from toppling over.

There is wind noise in that recording, but it’s produced more by the wind’s action on and around the baffle than on the mic diaphragms themselves. The Rycote Cyclone windshield halves seem to work well. Later, I moved the baffle to beside the long concrete wall bordering the Tilda rice factory nearby, and here the wind speed increases, perhaps by being funnelled along the wall. Close up I could see that the baffle was starting to shake and vibrate, and on that recording it began to produce brief audio drop-out where the diaphragms had likely hit their backplates. So 40mph gusts probably mark the maximum limit beyond which the baffle’s no good.

All sorts of improvements suggest themselves: carrying the rear-exiting cables beneath the surface of the wood, various ways to cut down on the baffle’s nearly six pounds (2.6kg) of weight, using Rycote lyre suspensions to deal with vibration, and making a fake fur cover to fit over the whole thing.

But, in the meantime, it is quite satisfying to have made something myself, and that does go against the grain of many hobby activities, which increasingly seem to be about simply buying the right components to fit together.

19 November 2016

Making a simple clamp for the Sound Devices MixPre-D

SOUND DEVICES are a US-based firm who make digital sound recorders. These are very expensive: even their entry-level two-channel recorder, the basic 702 model, costs around £2,700. They’re attractive and robust little machines filled with top-notch electronics ensuring extremely good signal quality. But, still, for that amount you could buy a saloon in reasonable nick and start work as a minicab driver.

Cost-conscious amateur recordists wanting to sprinkle a little Sound Devices stardust on their work can team the slightly more affordable MixPre-D with an inexpensive pocket-sized recorder, connecting the two via the latter’s line-in socket. This poor recordist’s 702 is capable of very good results. Some say the MixPre-D has the same preamps as the full-size recorders, others disagree, but I doubt I could hear the difference between the two.

Suppose you’d like to attach and detach the recorder from the MixPre-D in a quick and easy way. You could try gluing strips of velcro onto each, but this seems a crude approach. An alternative is to exploit a feature Sound Devices have built into the machine.

The upper side of the MixPre-D has two little holes for bolts for fixing on a special camera clamp, also made by Sound Devices. The clamp has to be bought separately and it costs around £130. It has to be a pretty amazing piece of kit for that much. Maybe it’s got an inbuilt talking spirit level urging you to go left a bit, up a bit, with Fenella Fielding’s voice. You can see for yourself on this webpage.

Or you can make one out of a small piece of 6mm plywood, two UNC No.6 bolts (this is a US-style thread size available from good hardware shops in the UK), some UNC No.6 nuts to make up to the bolts’ standard 50mm length, and a cheap quick-release camera clamp.

Cheap clamp for the MixPre-D

Just about all pocket-sized recorders have a camera tripod socket on their undersides, to which the quick-release plate can be screwed into. Now you can change in a couple of seconds from having the recorder securely attached to the MixPre-D to using the recorder freely on its own.

Cheap clamp for the MixPre-D with recorder attached

Total cost: about £10.

12 November 2016

A visit to the old nuclear weapons development site at Orford Ness

MY FRIENDS Iain Chambers and Kate Romano recently invited me to go along with them to Orford Ness on the Suffolk Coast. It’s a long shingly spit of land, the northern end of which extends to Aldeburgh, out of sight in the aerial view below.

Orford Ness can be reached by car and then a very short ferry trip across the river Alde. It’s owned by the National Trust who run it as a nature reserve. Many people will also know it as the kind of mysterious forbidden area which might have appeared in an old film like Quatermass 2, because it’s where nuclear weapons research was once carried out. Rutted roads and crumbling buildings are all that remain of a busy scientific and engineering community.

Public access to Orford Ness is allowed during daylight hours on some days of the week: most of the year it’s limited to Saturdays only. You can look at the bunkers from the outside but you’re usually not allowed inside, in case a rusting piece of pipework falls on your head. We were lucky in being given supervised access to the insides of the bunkers, some of which are called ‘pagodas’. Here are a few of the photos I took.

Below is the outside of a pagoda. The heavy roof is supported on concrete pillars and this was to minimise damage in case of an explosion inside the building: the blast wave would be easily vented to the outside well above ground level.

Inside was rusting switch-gear and other equipment.

The pagoda seen across an expanse of wind-swept shingle.

Inside the remains of a laboratory and administrative block.

More old equipment, possibly the remains of a heat exchanger.

Inside a workshop. The more luxuriant vegetation on the right-hand side conceals a deep, water-filled trough. H-bomb casings would have been assembled here.

There was quite a lot to look at, but not much to hear. The railings of a small lookout tower hummed and whined in the brisk wind. Inside some of the bunkers and other buildings there was the occasional clatter from loose fittings on ceilings being blown to and fro. Wading birds called out. Otherwise, near silence.

Orford Ness is probably worth a visit during fine weather if you’re already a fan of bleak-looking, peripheral areas like Dungeness. The National Trust’s approach here is one of managed decay with a welcome lack of obtrusive signage.

For a livelier, though not fatal, dose of Cold War nostalgia, you might also wish to consider a visit to the bunker at Kelvedon Hatch in Essex. I’m a big fan of those leaflets you find in hotels advertising local attractions, often with a scowling child in a pirate’s hat on the front, or a man my age pretending to be a Viking – Grimwald the Grizzled.

However, Kelvedon Hatch’s flyer takes some beating, with its lurid photo of an H-bomb explosion:

I went a few years ago and had an enjoyable afternoon. Also, keep an eye out if you’re driving there for an old-school roadside cafe nearby. It’s built to resemble a log cabin and there are few places like that left now.

19 August 2016

Audio problems for Android users

AN EMAIL ARRIVES from the United States helpfully pointing out that this site’s audio players won’t work on an Android tablet. I’ve since checked it on someone’s Android smartphone and find the same thing happening, or rather not happening.

Once upon a time the audio player, in its different visual forms, did work with Android but evidently times have changed. The only solution is for me to change all the players for a much newer version, which means redesigning and reinstalling them all from scratch. That’s not quite as bad as it sounds, since the pages here are dynamically generated, meaning only the templates need adjusting, but it’ll still take a while to get everything sorted.

For those interested in such things, the now-obsolete player was called Pickle Player. I’ll be replacing it with Wimpy Player, which is made by the same company. It looks pretty versatile and should allow for playback on just about every device around.