THE LONDON SOUND SURVEY BLOG

Occasional posts on subjects like field recording, London sounds past and present, other websites worth looking at, articles in the press, and news of sound-related events.

Building a field recording system 3: recorder accessories

Posted by IMR on 21 January 2012

THE PREVIOUS POST in the field recording system series looked at the Sony PCM M10 recorder and introduced a few technical concepts which are good to know about.

There’s a YouTube genre in which new electronic products are unwrapped by their purchasers. The excitement is all in the slow revealing, consumerism’s striptease glimpse of paradise, like some old sultan taking delivery of his latest wife.

On the plus side the videos show you what accessories are in the box. The PCM M10 comes with an AC adaptor, a wired remote control which will be useful for recording interviews, a wrist strap, a USB cable, and a CD with a basic version of Sony’s Sound Forge audio editing program.

What’s not included are decent rechargeable batteries, a case and, most important of all, a windshield.

TROUBLED BY WIND

Photography can draw on glamour and urgency: paparazzis chasing celebrities, nocturnal mementos from the fleshpots of the Balearic islands. Field recording is more about patience and stillness. You can’t imagine a film like Blow Up being made about a field recordist.

Handling noise caused by fidgeting with the recorder while it’s doing its job, or other self-made sounds like loud breathing and rustling clothes, are the equivalent of taking a photo with your finger over the lens. They’re distracting and should be avoided. Another common problem is wind noise and to deal with it you’ll need to buy or make a fake-fur windshield for your recorder.

Wind noise is caused by turbulence in the airstream buffeting the microphone’s delicate diaphragm. It’s recorded as an intrusive low-frequency rumbling noise which is very hard to remove in post-production. The long fibres of a fake-fur windshield work to dissipate some of the energy of that turbulence. At the same time, the open weave of the fur’s base material allows air molecules to carry their bump-my-neighbour propagation of sound waves through to the recorder’s mics.

I was going to record a before-and-after demonstration of how effective a furry windshield can be. But Vimeo contributor Joshua Denny has already made one involving a PCM M10:


Note how the windshield can cope with a draught of whatever velocity a fan produces, but don’t expect miracles in a Force 8 gale. The breezy conditions common in our maritime climate or the gusts deflected downwards to street level by tall buildings are what a fake-fur windshield can usually handle.

Sony make one for their little recorder, but it costs at least £50. This is a ridiculous sum to pay for a scaled-down version of the fluffy pencil case with wobbling eye-buttons that you had as a kid. Three other firms also make furry windshields for the PCM M10. They’re all cheaper, but they’re not all as good as one another.

Three different furry windshields


The one at the top made by British firm Rycote seems to take its inspiration from Dennis the Menace and his doggy pal Gnasher. The fur is quite short, and the whole windshield maintains a tenuous grip on the top of the recorder. It falls off quite easily and for that reason it’s not recommended.

Redhead are based in Hawaii and their windshields have longer fur and an elasticated, um, sphincter-like opening which grips the recorder firmly. They work well, as you can see and hear in the video above. Mine took just under two weeks to arrive in the post.

Redhead’s products are made in a range of sober and manic shades. If you want to record birdsong it’s a good idea to resist the urge to buy a red windshield, as birds spot red very easily with their excellent colour vision. Troll dolls are one of Denmark’s gifts to the world, not Hawaii’s, so the local culture theory falls down here.

Furryhead windshields come from Michigan. Although much of the best music has emanated from Detroit, the state capital, Alice Cooper and Ted Nugent are also Michiganites. It’s obvious that Furryhead’s products are rock-influenced and pay homage to 1980s hair-metal bands like Tigertailz.

BATTERIES AND CASES

Batteries last a long time in the PCM M10, but the two AA alkalines supplied by Sony aren’t immortal. Standard rechargeable nickel-metal hydride (NiMH) batteries might seem the obvious way forward, but they lose much of their charge over a few weeks when left lying around unused. Sod’s Law dictates you’ll want your recorder in a hurry only to find the batteries have gone flat.

Sanyo developed low self-discharge NiMH batteries a few years ago and marketed them under the title of eneloop. These hold most of their charge for at least a year when left alone. You never see them in the shops in Britain. Instead, a brand with the slightly unfortunate name of ReCyKo uses the same technology and these can be found in high street and retail park stores like Currys.

ReCyKo batteries and charger


They need a special charger which you can buy in a blister-pack along with four AA-sized ReCyKo batteries. It’s a good investment.

If you want a little case for your PCM M10, then ones made for Tom Tom-style satnav devices should fit just fine. They’re about £20 from PC World, or else around £10 from street market stalls.

The next post in the field recording system series examines how you can capture vivid and realistic stereo soundscapes with your compact recorder by using binaural or headworn mics.

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Building a field recording system 2: the compact recorder

Posted by IMR on 19 January 2012

THE COMPACT DIGITAL recorder is a device small enough to stuff into a trouser or jacket pocket. It’s a minor miracle of convenience and versatility compared to bulkier analogue ancestors like the Sony Professional Walkman. Prices have fallen as more manufacturers have entered the contest and current makes include Marantz, Tascam, Roland, Sony, Olympus, Korg and Zoom.

All these recorders are self-contained devices with built-in microphones for recording in stereo. Even basic models can produce uncompressed WAV files at high sample rates, as well as MP3 files. They’ll store the recordings either in a fixed internal memory, or onto removeable SD cards, or both. They’ll also have a USB port so you can easily transfer the recordings to your computer.

The Zoom H1 is the cheapest at around £80. The most expensive is the exotic Korg MR-2 at £550 and I don’t know anyone who’s got one. Both the Zoom H1 and the Korg are outliers which aren’t worth considering. This leaves a range beginning with the Tascam DR-07 at around £120 and extending to the Olympus LS-11 and the Sony PCM M10, both at around £230.

Because the price gap across that range of devices is only just above £100, it really is worth getting either the Sony PCM M10 or the Olympus LS-11. They have better build quality and make cleaner-sounding recordings because they have higher-quality components. You get what you pay for.

Some online comparisons pit the Olympus LS-11 against the Sony PCM M10. By far the best is on Robin Parmar’s Theatre of Noise website. The Sony machine may be a tiny bit better than the Olympus for the field recording system we’re going to build up, so that’s the one that’s going to be looked at here.

CLOSE-UP ON THE SONY PCM M10

As you’d expect from Sony, the build quality is good. The front of the M10 is mostly made of aluminium. The sides and back are plastic. The machine fits quite well into the hand and if you squeeze it you don’t hear nearly so many of the little creaking noises that you get with cheaper recorders.

All the M10’s buttons on the front require a fair amount of pressure to work them, thus reducing the chances of accidentally stopping or starting a recording. The familiar transport buttons of record, play and pause light up from behind to help show what’s going on. The menu system is easy to use, although there are a couple of functions which could do with being brought forward rather than listed inside the ‘detail menu’ option.

Sony PCM M10 front and side


The M10 comes with a generous 4-gigabyte internal memory and that’s enough to capture around 3 hours 40 minutes of audio at a decent archival quality setting of 24bit/48kHz. Battery life is superb and you may start to wonder whether the two AAs you put in at the start will ever exhaust themselves. It’s also got a screw fitting on the back so you can mount it on a camera tripod.

AN EYE ON THE LEVELS

Like all compact recorders, the Sony’s backlit display tells you how much time has elapsed, the current filename, the recording mode selected, as well as giving a rough idea of how much battery life is left. One of the more significant parts of the display is the levels meter marked in decibels.

Anyone new to sound recording might reasonably be baffled by the decibel or ‘dB’ markings on the levels meter. If the loudness of normal conversation is reckoned to be around 65dB when heard from a few feet away while virtual silence is 0dB, how can there be such a level as minus 6 or minus 12dB? Why doesn’t the levels meter begin at 0dB and go up to, say, 120dB?

The simplest answer is that although it’s using decibels, the meter’s telling you about audio signal levels inside the machine, which you control, rather than the actual sound pressure levels in the air, which you don’t unless you’re recording yourself singing in the bath.

Sony PCM M10 display


Decibels are unlike the measurement units we’re most familiar with, such as inches or litres.  Each increase of 10dB over some lower value means a ten times increase in the power or intensity of the sound: 20dB is ten times more powerful than 10dB, and 30dB is a hundred times more powerful than 10dB. This is a good way of condensing into manageable units the huge range of differences in sound pressure levels detected by our sense of hearing.

Decibels can also express the differences in the strength of audio signals in an amplifier or other electronic circuit. In the case of the M10’s levels meter, 0db signifies maximum power or gain, and as they grow larger the minus decibel values represent an ever-greater attenuation of gain. Minus 3dB is 50% of maximum gain, minus 6dB is 25%, minus 12dB is 6% and minus 24dB is just 0.4%.

It’s important to get the levels right while recording. The M10 has two coloured lights by each microphone which can help. A green light comes on when the level on that particular channel, left or right, reaches minus 12dB. That’s a desirable level for at least some situations or subjects. A red light comes on when the gain for that channel has reached maximum: time to move away or turn the recording level wheel down a notch or two.

Over time you’ll develop an intuitive feel for how to set your levels depending on where you are and what you’re recording. Don’t ever rely on the M10’s automatic gain control, or indeed that of any other recorder. The results often sound artificial and unattractive. It’s much better to learn about levels through practice.

BUT HOW DOES IT SOUND?

Many reviews of the M10 have praised how quiet or clean its mics sound, meaning they don’t have as much of the hiss and sound colouration that’s noticeable with really cheap kit. Two little mics built into a £230 recorder aren’t going to sound as good as a £450 stereo mic like the Audio Technica BP4025 or a couple of DPA 2006C mics at £1,200 a pair. But they’re not bad and, as stated in the first post in the series, the best recording equipment is always what you’ve got on you at the time.

Here’s a couple of admittedly lazy, opportunistic tests edited together. The first part was made in a lift at work and the second at St Pancras station while waiting for the train home:


The lift recording isn’t particularly useful although there’s no apparent hiss in what was a fairly quiet environment, and the sound of someone jingling keys close by is reasonably well localised. The train station recording is lacking in drama and oomph – in reality people on the platforms at St Pancras often wince at the sharp squealing sounds of the wheels. It’s also hard to work out from the recording in what directions the trains were moving. The M10’s mics produced a poor stereo image in those surroundings.

The Wingfield Audio website has a very useful page of recording samples made with a range of recorders. The M10’s internal mics do well with the isolated, clearly-defined sound sources of a cello and someone talking.

GOING FOR GROWTH: MIC AND LINE INPUTS

One of the goals of the field recording system is to work towards bypassing the recorder’s internal mics and preamplifier in favour of higher-quality external devices made for doing those particular jobs and nothing else. The recorder will then be used for its handy display, analogue-to-digital converter, and file storage only.

On the top of the M10 are the mic and line sockets which will make this possible. It’s a convenient enough place to put them, too.

Sony PCM M10 top


The bottom of the M10 has a tiny loudspeaker which isn’t useful for much, except perhaps to reassure you that you have actually managed to record something other than silence.

The mic socket is the one on the left in the picture and it has two functions. First, it’s designed to deal with audio signals of mic level strength coming straight from an external microphone and hence relatively weak. The M10’s preamplifier, the same one used to increase the gain of its internal mics, will also increase the gain of a signal reaching it through the mic socket to line level.

The mic socket’s second purpose is to provide plug-in power for any external microphone which needs it. Plug-in power is a low-current supply of around 4 volts and it’s used to drive small microphones called electret condensers or just electrets for short. They’re commonly used as pairs for binaural recording, which we’ll examine in a later post. (The leads from a binaural pair will converge at a single 3.5 mm (1/8”) jack, so you don’t need two mic sockets.)

The line-in socket is a much simpler affair. It can’t provide plug-in power and it’s designed for audio signals which have already been raised by an external preamplifier to line level. A signal reaching the line-in socket therefore bypasses the M10’s preamp because it’s assumed that it doesn’t need to have its gain increased by a large amount.

Yet if you turn the recording level wheel while the M10 is recording an audio source connected to its line-in socket, the levels meter will show the gain increasing or decreasing accordingly. If the M10’s preamp has supposedly been bypassed, what’s causing this to happen? It may be that a different circuit is involved, and if so it’ll be simpler than the preamp because it isn’t designed to increase the gain nearly as much.

This post has touched on technical concepts such as decibels, gain, line level and mic level. It’s useful to have some idea at the outset of what they mean. Next up is a look at the most basic and essential accessories you’ll need to get the best out of your compact recorder.

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Building a field recording system 1: introduction

Posted by IMR on 12 January 2012

THIS IS THE first in a short series of blog posts in which I’ll present some thoughts on how to build a system of field recording equipment.

System, along with dynamic and terrain, is one of those decisive-looking words which is often used to prop up vague ideas. So why not talk about assembling a collection of field recording equipment?

A collection can be built up haphazardly without any forward planning. If you collect say, cigarette cards, you’ll often buy them as sets, which can lead to you owning duplicates. The loss from buying something which becomes a duplicate is the price of uncertainty. You can’t be sure what will turn up at the next auction or car boot sale.

Someone who wants to get into field recording faces the uncertainty of not knowing how far their interest is likely to develop. Perhaps the low-cost compact recorder they buy today will stop being satisfying to use after only a few months. It may even be that it isn’t equal to some specific recording goal from the very outset.

SIX BASIC GUIDELINES

The system of field recording equipment I’m going to describe over the next few posts is based on these rules of thumb:

1. The best field recording equipment is always that which you have on you at the time. The more bulky the equipment, the more reluctant you’ll be to use it regularly.

2. The cost of field recording equipment is generally a good predictor of the quality of the sound recordings it can produce . . .

3. . . . but there are situations and environments where this makes little perceptible difference, and where smaller and usually cheaper equipment will be more practical.

4. Building a system of field recording equipment means keeping an eye on future possibilities so you don’t waste money by making your early purchases redundant.

5. The foundation of the system is the compact recorder. With this alone you’ll be able to make enjoyable recordings. By adding new components you’ll expand the range of situations and environments in which you can make such recordings.

6. In its later stages the system involves spending the most money in total on the most important part of the recording chain, the microphone.

WHAT THIS ISN’T GOOD FOR

All this is based on my own experience as someone who enjoys field recording as a hobby. The work of professional field recordists in TV, radio or film can be very different and much more demanding than what I’m used to doing. So if you’re looking to earn a living from field recording, you’re better off seeking advice on something like the Social Sound Design website.

Gadgets are marketed by appealing to our desire to be thought of as competent by others. The success of that approach can be seen in the intense online arguments over the merits of different devices which are almost identical in function and quality.

But even the very best recording equipment cannot begin to fill in the gaps left by an indifference to sound, or where the urge to learn and experiment is lacking.

The next post in the series looks at the compact recorder, the seed from which the rest of the system will grow.

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Where Londoners come from

Posted by IMR on 11 January 2012

HERE’S ANOTHER RECORDING from the Waterways sound map made last Friday by the river Lea. The Lea remains London’s most industrialised minor river, even though most of the valley’s factories and paper mills have now disappeared.

Just north of the Cooks Ferry roundabout the Lea passes a collection of large waste recycling plants. A row of trees stands between them and the west bank of the Lea. Dozens of rooks had convened on the branches.


The rook’s efficient respiratory system absorbs atmospheric pollutants at a high rate. It expels them by hacking up rich gobbets of phlegm, accompanied by the rattling vocalisations you can hear in the recording.

On reaching the ground each phlegm-clot begins forcing a network of fine roots into the soil to extract trace nutrients such as cadmium and mercury. Meanwhile the clot becomes cold and firm to the touch as it swells into a puffball-like mass known as the sacculus. In time this ruptures and out crawls a new baby Londoner.

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Nice to meet you, London Historians

Posted by IMR on 05 January 2012

THE BAD WEATHER had stopped me finishing off the London Sound Survey’s Waterways soundmap. Instead, the week I’d booked off work was starting to feel more like living la vida doley. Hours spent indoors were broken only by raiding trips to the corner shop for biscuits and teabags.

High winds are usually the enemy of field recordists. Turbulence in the airstream moves chaotically over the microphone diaphragm and makes a low-frequency rumbling which is very hard to get rid of in post-production. Even the standard fake-fur-covered microphone windshield isn’t always of much use.

Away from built-up areas there are often trees and bushes nearby and their leaves make a featureless hissing when the wind agitates them. It’s one of those sounds which somehow doesn’t lend itself well to recording, like the way the iridescence is lost from an insect’s eyes when it’s dead and pinned as a museum specimen.

Instead of going stir-crazy though, I had last night’s London Historians pub meeting in Victoria to look forward to. Matt Brown of the mighty Londonist had told me all about it, and I was really glad I went. Not only was it in one of my favourite central London pubs, the Windsor Castle, but the people there were friendly, welcoming and interesting. It was a very pleasant evening and I’m already looking forward to the next London Historians pow-wow.

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