Contact microphones are actually piezoelectric transducers and are mostly used for producing sound as buzzers, beepers and small speakers in electronic devices. If the signal is reversed using a piezo transducer as a mic, you’re actually picking up vibrations and having it produce voltage. Connecting this to a recording device or mixer allows you to hear the vibrations as sound. Piezo transducers come in all shapes and sizes, the most common ones ranging from 25-50 mm in diameter. They can be ordered from electronics components distributors such as Maplin in the UK or DigiKey in the US. As for what kind of disc to buy this is a question of great debate, but I generally stick to mid sized discs of 30-40mm with a resonant frequency of 1khz. Best of all they are cheap, usually 50 cents or so.

As for building contact mics, the process is fairly simple. A soldering iron and raw solder is needed. Some flux paste is helpful for getting the wires to stick more firmly. As you can see some piezos come with leads already attached. All you need to do is connect then to a wire and the appropriate plug. The center circle of the disc is the ceramic piezo element (what produces voltage). The ‘hot’ lead needs to be connected to this and the ground needs to be connected to the outer metal part.

What plug you use depends on what kind of device you use for the signal. Most likely you will connect your contact mic to a mixer or directly to a recording device such as a flash recorder (Sony PCM-D50, Edirol R-9, Zoom H4 etc.) or Minidisc. I often work in the field and connect my contact mics as a stereo pair to a flash recorder with a 1/8″ mini-jack.

To make a stereo pair, simply solder up two single discs and attach the ‘hot’ leads to the two center signal leads on the mini-jack plug. Be sure to insulate any contact to avoid shorting the signal.

Finalizing your contact mics is an important step. Piezo transducers tend to be fragile. If the ceramic crystal is damaged in any way you’ll immediately know it. At the very minimum its good to put some kind of glue over the back of the disc to protect the crystal. I sometimes put the felt furniture pads that are used on chair leg bottoms over the crystal to protect it then I cover the whole disc with electrical tape. I also glue a thin piece of wood to the front side with epoxy. This is to make sure the disc does not bend and crack. The wood also “softens” the sound as piezos tend to have a sharp metallic sound (since they are actually made of metal). Some people also coat their mics with something like plastidip which makes a nice clean protective finish.

Another reason to protect the piezos is because they tend to work better when a bit of pressure is applied. The sensitivity increases and you tend to get much better bass response. With the felt furniture pad backing and wood front I’m not afraid of bending the disc or crushing the ceramic part when using clamps or clips. Its also handy to use something like blue-tack to make a firm connection to the surface of what you are trying to record.

It is good to carry around a number of different clips and clamps for the materials and situations you might encounter. Most of these are cheap and lightweight and can be found from most building supply stores.

Lastly, this is a device I often use when recording with my contact mics. The FEL Microphone Amplifier is small, runs from a 9V battery and can boost a stereo signal up to 50dB. This really helps when the source is more quiet or you want to pull some bass out. Most of the time I need to boost the signal about +15-30dB, but occasionally you need more.

For examples of my recordings using contact mics check the posts with the tag *contact mics*

The two digital recording devices used are the Edirol R-09 and a Sony PCM-D50. For some some microphone tests and personal commentary on these check here and here.

Hopefully this helps anyone who is interested in working more with contact mics. Most importantly, remember there are no fixed rules about the best ways to use contact mics and it a matter of continuous experimentation. I will update this page if more questions or info comes in.

*UPDATE*

I made a simple set of contact mics for XLR plugs. I search around for some basic designs and didn’t find much. Here is what I came up with for a setup. I used 2 piezos instead of 1. The center ‘positive’ leads of each piezo are connected to the 2 and 3 leads of the XLR cable, while the outer ring (ground) of both piezos are connected to the 1 (ground) lead of the XLR cable. The diagram can be seen in the first photo. Some have noted that this wiring should ‘phase cancel’ yet for some reason it works. If you encounter problems, simply use a single piezo and do not connect anything to the negative #3 lead.

The tops faces of the piezos are turned inward toward each other. On each face is a self-adhesive felt circle (for furniture legs). Once the two felt circles are in place they can be glued together with a semi-flexible glue like ‘moment glue’. In this case the felt circles were smaller than the piezos so I wrapped the edges with nylon string and filled it with epoxy for strength. When this was done and all glues were dried I wrapped everything with electrical tape. The result is sensitive, low noise, contact mics. All this (good cable, neutrik plugs, piezos, felt) still cost lest than 20 euros.

Click here to view the embedded video.

Recording a suspension bridge (above).

Below is a video from MAKE Magazine about building a contact microphone that includes the schematic plan for a 9V powered amplifier. The amplifier can be handy if you don’t have a suitable amplifier on your recorder.

Click here to view the embedded video.

Recording fences in Avebury UK (below).

This is a great hydrophone recording I made last week in the local Mooste lake. The sun was shining brightly so the plants were giving off plenty of oxygen. There are also a number of sqeaks and buzzes I cannot yet identify. The hydrophone is made by the avid field recordist Jez riley French who spent a few weeks in the MoKS residency. I can reccomend these hydrophones for those who want to try out under water recordings and are on a budget (yes, this is a small but honest advertisement for Jez’s product which he sells to help fund concet events he organizes).

hydrophone recording of Mooste lake #2: download link

For now I decided to focus on the Sony PCM-D50 and what kind of recorder you get “out of the box”. I don’t have a new Edirol HR-09 to test and I wouldn’t recommend getting the old model. The Sony unit feels sturdy and seems well made, even more so than my old Sony minidisc machine that lasted 8 years (and still somewhat works). My dream is to have a modern electronic device that lasts more than 10 years. Is that so much to ask? I don’t think so since the first recordings I ever made (in the late 80′s) were on a reel-to-reel tape recorder that my father bought in the early 1960′s and still worked fine. Anyway, I went out today to make some “field recording” tests, particularly in quiet conditions. As you can see from the photos, everything is covered in snow, which heavily dampens nearly all sound reflections (I love this effect). On the first recording I’ll highlight the general capability of the built-in mics, which is that they are very sensitive and pick up distant sounds fairly well. For all these recordings the mics were placed in the 120 degree ‘open’ position.

General ambient sounds in the village with some close sounds coming from dripping drains (I even boosted the levels a bit):
dripping water drains with ambient sounds

The last two recordings reveal some problems. One big problem is that with really quiet sound sources you can’t hold the recorder without getting some form of body noise. Even when I put it on a tripod I had to be careful not to move at all otherwise it would pick up vibrations. Also some self-noise from the mics starts to appear. Ambient recording near frozen lake:
ambient recording near frozen lake

Even more problematic though, for recording is wind. While this is normal, one would think that the (totally over priced) wind screen would help. It could be that, the mics are so sensitive, any wind will affect them. That’s understandable to a certain extent, but the “wind” in this case was a light breeze, something you would expect on any normal day. The wind screen didn’t seem to help much. I turned on the low cut and limiter switches, but the recording is still seriously affected by the mics totally blowing out:
ambient recording near frozen lake in a light breeze

The solution of course is to use external microphones. No problem really except that you might want to occasionally take advantage of having built-in mics for certain spontaneous situations. The dilema here is if you can really depend on them if it’s not a perfect wind-less day.

When dealing with recorded sound, technology plays an essential role in nearly every step of the process. While I focus a great deal of attention on acoustic sound, the capturing, editing, processing, compressing and sharing of those sounds, all relies on and is affected by, technology. This is a very general intro and overview to some basic recording technology that I use. The methods used here are definitely not scientific by any means. With a bit of searching you can find more in depth reviews as well as well researched technical analysis of these devices. What’s shown here is just to give an impression. All this equipment is reasonably affordable and can help beginners get a start on working with sound as well as keep artists like myself busy. The main point I feel is accessibility and ease of use.

The two digital recording devices used are an Edirol R-09 and a Sony PCM-D50. The Edirol unit I’ve had for almost 2 years and I can say its a handy little unit that works well for most occasions. One of the main reasons I bought it was to be able to use rechargeable AA batteries so I wouldn’t have to worry about running low on power if I kept extra batteries handy. Its well worth it for the quality and flexibility it offers. The main drawbacks are durability and a weak preamp for mics. The device is pretty much made of plastic. While nothing has broken so far, I’m constantly concerned about how long it will last. As for the preamp it just doesn’t ever seem to have enough power and is a bit too noisy. For this reason I bought a FEL Battery Preamp, a great device for boosting any any signal to line level, including contact mics (to bypass the mic input). I think the revised R-09HR model made by Edirol has improved some of these issues.

The Sony PCM-D50 is still new for me, but immediately I can say it feels much more sturdy than the Edirol and has better quality built-in microphones. This of course makes it slightly larger and more heavy if you’re concerned about portability. For external microphones I’ve used a selection of cheap to mid-level to compare (and also because it’s what I have around). I started with the mics built into the recording units themselves. These are good for general use but you will definitely need to have a few different kinds of mics around for recording specific types of sounds or sound environments. Here’s the breakdown:

• Audio-Technica AT822 – well made single point X/Y stereo mic, good for general use and capturing close sound sources.

• Sound Professionals SP-BMC-12 mini-binaural mics with Audio-Technica capsules (discontinued?). I’ve had these mics for over a year and have enjoyed using them. The problem you will notice is that they are not very well matched. The left mic is louder than the right one.

• Homemade binaural microphones with Panasonic WM-61A capsules. There is a lot of info on the internet regarding these capsules. In short, they are one of the best deals in audio recording, with their open sound and flat response. These binaurals cost me about 7 euros in arts and sound as good as anything you can find up to 150 euros.

The sound clips below are divided into 15 second segments and are repeated twice, once to compare recorders and once to compare microphones. Again this is not done in any scientific manner. I just placed the mics about 1 meter away from the sound source. In this case it was a fire for the oven that heats our house. The high pitched noise is a refrigerator on the other side of the room.

Recorder | mics:

Sony PCM-D50 | built-in mics, Panasonic binaurals, Sound Professionals, Audio Technica AT822 (15 seconds each): Sony PCM-D50

Edirol R-09 | built-in mics, Panasonic binaurals, Sound Professionals, Audio Technica AT822 (15 seconds each): Edirol R-09

Edirol R-09 with FEL preamp | built-in mics, Panasonic binaurals, Sound Professionals, Audio Technica AT822 (15 seconds each). note: I think the battery in the preamp was low giving weaker levels than normal: Edirol R-09 with FEL preamp

Mics | recorder:

Built-in microphones | Sony PCM-D50, Edirol R-09 (15 seconds each): Built-in microphones

Panasonic binaurals | Sony PCM-D50, Edirol R-09, Edirol R-09 with FEL Preamp (15 seconds each): Panasonic binaurals

Sound Professionals SP-BMC-12 | Sony PCM-D50, Edirol R-09, Edirol R-09 with FEL Preamp (15 seconds each): Sound Professionals SP-BMC-12

Audio-Technica AT822 | Sony PCM-D50, Edirol R-09, Edirol R-09 with FEL Preamp (15 seconds each): Audio-Technica AT822

notes: Plug-in power was used on the Sony and Edirol recorder sn all cases. It is possible to change the direction of the built-in mics on the Sony from a 90 degree X/Y pattern to a wide 120 degree L/R pattern. For this test I kept the mics in the X/Y position. All MP3 files are compressed at 160kbps. In the second part I will use recordings of more ambient/environmental sounds.

This past weekend was in Madrid for the Sonikas festival where I performed. While there, I learned about several sound-mapping projects in Spain. As some know, I contribute to Radio Aporee Maps, a growing collection of sounds from around the world which are playable in several ways. The projects linked below are more regional, focusing on specific areas within Spain. With sound-mapping being an expanding phenomenon, it will be interesting to see how it develops.

Escoitar http://www.escoitar.org/
Soinumapa http://soinumapa.net/
Madrid Soundscape http://www.madridsoundscape.org/

Special thanks to Mikel for introducing me to these projects and to Alfonso, Juan Carlos and Molino for their sincere organizational efforts. Below is a recording of a pet shop in Madrid that specialized in singing birds.

birds in pet shop

This is a question I’ve been asking myself ever since I realized that “field recording” was something of a viable genre for many working with sound. Before hearing the term “field recording” (and I’ll throw in Phonography), I never thought much in making a distinction between working in or out in the field. I recorded what I wanted and where I wanted (and still do).

While some view it as a recording technique for any place other than the studio, others seem dedicated to the cause and strive to reach new levels of purity. The spectrum of approaches is wide from scientific ‘nature recording’, and commercial ‘relaxation environments’ (some may know the interesting ‘environments’ series from the 70s) to weekend hobbyists who simply like to get our and record sounds they like.

Like any term, the definition is open to interpretation. The artist Jez Riley French has opened up the discussion with his ‘four questions’ series regarding sound artists/musicians and their use of “field recording” in their work. Below is the current list of artists Jez has included in his survey which I feel is more than worthy to help promote. I’m sure more are on the way, but this should be more than enough to start with:

• Andreas Bick
• Cedric Peyronnet / toy.bizarre
• Eric Cordier
• Goh Lee Kwang
• Jean Francois Cavro
• Jez riley French
• Jez riley French interviewed by John Grzinich
• John Grzinich
• Kiyoshi Mizutani
• Lawrence English
• Maksims Shentelevs
• Marc Namblard
• Matt Davis
• noid (Arnold Haberl)
• Patrick Farmer
• Rob Curgenven
• Simon Whetham
• Thomas Tilly
• Zoe Irvine

Yannick Dauby makes and important point  in his description of “Field recording and phonography” as to why we who record sounds in the field are shaping the sound as much as we are simply capturing it:

“The couple microphone/headphone acts as a filter and an enhancer for perception. The use of these tools is absolutely not neutral : the choices of the place and the moment, the gestures, the technical limitations and the zoom/macro effects of the microphone affect the result of the recording. The recordist makes a series of decisions in his practice, and these decisions are related to his own subjectivity.”

Numerous other in depth perspectives on the practice have emerged in recent years, I suspect due to the availability and ease of use of digital technology. People like Aaron Ximm (Quiet American) and Patrick McGinley (murmer/framework) have been long term proponents of creative uses of filed recordings and seem to have inspied many through their output. As the “field recording” bug spreads I suspect we may see ever more variations and mutations on what this is about. As for listening to field recordings it’s a fertile matter for another post.

Taking sound as an artistic medium unto itself, what interests or motivates you to work with sound? Is it some form of “musical” drive or is it a more abstract and less tangible means of expressing something?

JrF: well, with this first question I already feel the weight of the limits of language for me. I find it quite odd to explain really. I just started making music when I was quite young & for me I believe I have progressed naturally to the point that I’m at now. By ‘naturally’ I mean that I gave myself time, I worked intuitively and whilst that means a longer journey than perhaps achievable by constant formal study, I feel this was the only way for me to be. So I make the music that I enjoy making. I engage in the creative act when I am moved to do so – it feels natural and a part of my way of being. I think music is a part of it all – the way I think and feel, the way I read, the way I cook and eat, the way I watch, the way I take photographs etc. etc. So I guess, going back to your question, what motivates me is as abstract and intangible as life is and as tangible as the moment to moment way we find to enjoy or cope with life. Working with music / sound & simple visual elements (photography, drawing) is the way I feel able to express myself.

What are some of the challenges in working with sound, both personally for yourself and for what you present to the public (live for an audience or as published work)?

JrF: These are good questions ! you see I really feel that the challenges, the ebb and flow of undertaking these things are private. I could say that, for example, I only make recordings when I feel ‘right’. Sometimes I come across a sound that I like to listen to but I don’t record it – I don’t feel right about it. I don’t really give myself any set expectations. I’m not someone who goes out hunting for an unusual sound. I just live and my creativity is an emotive response. That’s a term I use a lot because it’s the most descriptive phrase I can think of to explain.

In terms of releases, I simply put out the recordings I enjoy and that remain enjoyable or that I instinctively feel are right to release. Perhaps this is where the element of the unexplainable starts to make a difference – like a photographer who is said to have ‘an eye’ I suppose I trust my ear & am quite happy to stand by those choices.

Live performance has always been part of my musical life. I started out playing guitar & was in bands & performing solo from early on. I got really into music around the time that new wave / punk music hit the UK so it was all about just getting out there & playing. These days I have a fully formed set of things that cause me stress when performing, but those relate mainly to the organisational aspects. I like to have a nice, friendly time with the folks arranging the concert / event & a stress free soundcheck + an audience who respect music / sound. So all the challenges relate to aspects other than the actual music. Once I’m performing, working with intuitive composition, it all boils down to whether the piece ‘works’ or doesn’t & whilst one always hopes it does I suppose I rely on my instinct. There might be challenges but again, I feel these are private and more to the point are different with each performance.

I understand you do a lot of site-specific work, recording in particular locations and improvising with what you find. Can you talk about why this type of field work is interesting for you as opposed to, let’s say, only making studio based work? Are you attracted to certain locations more than others or do you look for certain types of locations?

JrF: it’s a simple story – I often found myself performing in spaces that I liked & wanted to record the sounds I found. I did that for a long time & avoided using the term ‘site-specific’ – by & large I have a difficult relationship with what I term ‘art speak’ but that’s a different story. I suppose when I improvise or compose live with instruments the sound of the space one is in has a direct effect & so, when using field recordings I find it enjoyable to incorporate the sound of the performance space too if possible. It’s not something I always do – again, it has to feel right.

I don’t really look for locations all the time. Sometimes I will go out with the intention of recording a church or some water (a river or the sea for example) but I often find that these more deliberate attempts result in recordings that might be ok but perhaps lack a certain something. It’s nearly always the happy accidents, the sounds one stumbles across that provide the most pleasing results.

I am attracted to the locations that I like – simple as that. What I’m trying to say is that I am attracted to places as a person & not as a field recordist.

Continuing with the topic of site-specific work and field recording… What is it you like others to hear from the places you visit and record? Why should we at all record the sounds we hear or the music we experiment with in these places?

JrF: well, putting aside the question of whether one can ever know or control what the audience hears, I always hope that an emotive impression is communicated to those who are able to listen in that way. It’s not possible if the audience is full of males who are more interested in the equipment being used than the music though ! or indeed if one is performing to fellow field recordists who are just waiting to hear something they haven’t heard before. This is one reason why I use the term ‘music’ rather than a term such as ‘sound art’ – for me it is that essential quality that makes music ‘sing’ that is the key.

I think, as I said earlier, the music and sound of places is enjoyable whether it is recorded or not of course. For me, the act of recording is a gentle intervention and I never force it – if I don’t feel right recording then I won’t.

What is your relationship to the technology you use for recording and listening? How dependent are you on technology and what kind of standards do you have?

JrF: I would describe myself as an technophobe ! I like equipment that I can be intuitive with and that is immediate. I started out using portable tape recorders back in the early 1980’s & then moved to minidisk – which I still use because I like the portability. I have never been one to rush out & buy the latest bit of kit – I prefer to fully explore the possibilities of the equipment I have. In fact I have a guitar multi-effect unit that I’ve had for about 10 years I guess & it’s still on the first patch !

However, as my interest in recording very quiet sounds – audible silence & sonic architecture – has developed I have invested in a high quality CF recorder (Sound Devices) & a variety of different mics.

I make my own contact mics & hydrophones too. I guess I’m a bit like the stereotype Yorkshireman – never spend a pound unless you have to!

I treasure the exploration & the moment of discovery so in that respect the technology involved isn’t key. I capture those moments using whatever kit I have with me & I’m really not someone who spends hours setting up a recording in order to capture some perception of a ‘perfect’ recording. For me not only do I believe that that doesn’t exist, but even if it did I wouldn’t find it interesting for long. Much of what I don’t like in terms of music, sound & in this context, field recording is technically very high quality but lacks the emotional aspect, lacks the sense of having been captured by a person with a mind and a heart, with strengths and faults – I guess I feel it is dishonest in some way. So my standards would seem lower to some other artists who value the technical perhaps, but I feel my standards are very high – you can easily buy better equipment but you can’t buy better ears or a better connection to your emotions and inspirations !

The material list is as follows: shielded stereo cable (at least 2m), 2 plastic ‘feet’ (for table or chair legs. make sure one is slightly smaller than the other so as to fit inside the larger), 2 small piezos (21mm), stereo mini-jack plug (use whatever plug you need), 1 or 2 nuts, epoxy (for plastic). Besides this you will need a soldering iron and some solder to connect the cable to the plug and piezos.

To start with you need to solder the piezo to the cable. The center goes to the positive and the ground goes to the outer ring.

The first question most people will have is, why am I trying to make a stereo contact mic? The answer is, I’m not. Most portable recorders use a stereo mini-jack input but not all allow mono recording (at least my Sony PCM-D50 doesn’t) so wiring this in stereo is better than making a mono one and only monitoring in one ear. Besides, for this simple design, maybe 2 surfaces is better than one. If you have a mono input on your recorder than you can simply use one piezo. Before you move on, test the piezo to make sure it works.

Once the piezos are properly soldered the hydrophone is ready for assembly. Epoxy is great but its toxic so be sure to work in a well ventilated space. I put things together in this order to insure a solid construction.

1) epoxy the piezos to the bottom surface of the plastic feet. Push it down firmly as to have as much full contact as possible. Allow the epoxy to harden
2) mix a little bit of epoxy and cover the backs of the piezos to make sure the solder connections are covered. Allow the epoxy to harden
3) Epoxy a metal nut (or lead fishing weight) inside the smaller foot. Allow the epoxy to harden
4) Use a generous amount of epoxy to cover the inside surface of the larger plastic foot. Then carefully slide the smaller foot into the larger one until the two are firmly sealed together.
5) seal the outer edge with a small amount of epoxy. Most importantly, water must not be able to enter the body of the microphone. If it does the solder connection at the piezos may short and you will not get any signal.
6) Once all the cracks or holes are sealed and the epoxy is set, the hydrophone is ready to use!

Original pair of hydrophones I decided to build (but then lost) after hearing some good recordings and discussing with others their experiences. There are several design plans offered on the web. Due to simplicity and availability of materials I settled for the Hydrophone Construction Manual. Below are two recording samples I made recently. While my results may not meet any scientific standards I’m still fairly impressed with what I was able to hear.

It is spring time in Estonia so the local lakes provide a good source of sounds. Hydrophone recording of Mooste lake: mp3 file

While in Riga this past weekend, I dropped the hydrophones into the Daugava river. Sounds of motor boats in the Daugava river: mp3 file