Radio Microphones and Field Recording

I have been wanting to test the use of radio microphones for my field recording work for a while now. I finally got round to it.

Radio mics or wireless microphones are two terms commonly used for a number of different types of devices. In the broad sense the terms refer to any wireless system used to transmit audio signals over a wireless connection. In a narrow sense the terms refer to a wireless enabled microphone such as the Shure SM58.

Wireless systems are common in concert, drama and film applications both for PA and monitoring. Singers performing on stage use dynamic or condenser hand held microphones with a wireless transmitter built in. In drama/theatre or film it is mostly lavalier microphones connected to a wireless transmitter body pack that are being used. All of these systems usually use the UHF 470 MHz to 870 MHz bands for transmission. Which frequencies you will be able to use is dependent on country specific regulations. Often you will need a license to be allowed use of the equipment.

Wireless microphone systems operate in the same frequency ranges as TV channels and wireless internet (wireless DSL). As of 2012 the new LTE (4G) mobile phone networks will impact the usage of wireless mics and wireless personal monitors quite heavily. Strict usage regulations to be expected.

Manufacturers like AKG, Sennheiser and Shure have wireless systems in their product offering but these are geared toward stage performance. For field recording one needs to look at wireless systems for ENG/ EFP applications. To me only two manufacturers offer systems potentially of interest to the field recordist: Lectrosonics and Micron. Their hardware fits in an audio bag, the build quality is rock solid and the audio quality is excellent. I am ruling out Zaxcom because their systems low pass everything at 16kHz.

The obvious advantage of wireless is mobility. No cable clutter and less weight to carry around. But what about audio quality?

I tested the Micron TX700B transmitter SDR550 receiver combination with a DPA 4060 miniature microphone.

Frequency response of this system is 80Hz to 20kHz. S/N ratio is better then 100dB. The receiver uses a diversity design meaning two antennas are used to prevent audio from dropping out. This works really well. I have experienced no audio drop-outs even in the RF hostile city where I live.

Much of the discussion on audio quality in wireless systems evolves around the companding that is used on the radio connection. The dynamic range of the audio is compressed on the transmitter side, usually in a 2:1 ratio. An expander restores the audio to the original values at the receiver side. Depending on the technology used side effects referred to as “breathing” can sometimes be heard as a result of this signal processing. The “breathing” can occur by a sudden rise in the noise floor on quiet sections of the audio.

Here again the Micron system performed extremely well without any side effects.

In all I am quite happy using this system for field recording use. I can position the DPA microphones in locations I would be unable to reach using cables. The audio quality is more then acceptable. I have had no trouble with signal strength with distances as far as 80 meters.

I will continue the testing with phantom powered condenser microphones, probably the Sennheiser MKH 8020.

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Audio Media 2010 Top 5

2010 also was the year where more musical inspiration and ideas came to me through on-line media then ever before. Probably why I have six entries in the top 5. Some of the entries are on-the-air radio stations with internet presence, others are streaming media only. And it’s not just audio either. In my view important curatorial work and sustained effort is done here:

Framework Radio; http://www.frameworkradio.net; run by Patrick McGinley and broadcast on-line on Resonance 104.4 FM. Dedicated to phonography, field recording and it’s use in composition,

Fluid Radio; http://www.fluid-radio.co.uk; true internet radio for experimental acoustic and vocal work,

Klara; radio.klara.be; the Brussels, Belgium based radio station’s Mixtuur show airs and streams live Monday though Thursday. Arnold Schönberg to Max Richter and everything in between and on the side,

Mixcloud; http://www.mixcloud.com; while very diverse in broadcast categories has selections brought together by Taylor Deupree, Seaworthy and Matt Rösner, Celer, … and check out Mary Ann Hobbs,

Take Away Shows; http://www.takeawayshows.com; music video documentaries from all over produced and directed by Vincent Moon (and others). A minimal approach brings out the love for the artists and the artists’ passion for their music,

Touch Radio; http://www.touchradio.org.uk; published by Touch at regular intervals always comes up with creative work in areas such as field recording, sound installations and performances. New and unexpected with every issue.

Field Recording 2010 Top 10

2010 has been a year with amazing field recording work hitting my radar screen. So much so I decided to compile a top 10 of the year with the work that has made the most impression on me or influenced me to considerable extent.

Not all of the work listed was published in 2010. And not all of the work are albums or CD releases. Field recording artists use Bandcamp and Soundcloud as much as any other artist. Perhaps even these media are more important to sound artists compared to others to get their work the exposure it deserves.

My selection is not exclusively ‘field recording’. Some of the releases are musical compositions that take field recordings as their building blocks. All of the releases I feel are explorations in sound.

Jana Winderen, Energy Field, Touch
Seattle Phonographers Union, Seattle Phonographers Union,  and/OAR
Chris Watson, Jana Winderen and others, Sleppet, +3dB Records
Francisco Lopèz and others, Dérives, Universinternational
Seaworthy & Matt Rösner, Two Lakes, 12k
Richard Ranft, Rainforest Requiem, British Library Sound Archive
Solo Andata, Ritual, Desire Path Recordings
Mark Brennan, wildearthvoices, soundcloud.com/wildearthvoices
Louis Antero, Sound Narratives vol. 3, mimi
Surround2011, Zushi Sound Map, surround2011.bandcamp.com

Portable Audio Recorders

For a few years now we have seen a wealth of portable audio recorders appear in the market. Most record two tracks at 96 kHz, 24 bit and have integrated stereo microphones.

While the 96 kHz, 24 bit suggests high quality audio recordings it is the integrated microphones that spoil it all.  Unfortunately not many manufacturers document the specs of the microphones on their devices. Even elementary information like whether the mics are cardioid or omni is often lacking. Instead we are left with descriptions like “Internal Stereo Microphone”. No noise performance indications or frequency response information. Clearly a sign most of these devices are not positioned as devices for the professional sound recordist.

Luckily a few websites come to our rescue. Of note here are www.wingfieldaudio.com who provide excellent noise floor samples and www.avisoft.com who provide both noise floor samples for a few models and EIN data for a fairly complete range of portable recorders available in the market today.

In my experience an Equivalent Input Noise number of -120dBu, unweighted and at maximum gain setting is the minimum for the field recordist to be able to make decent recordings. Also, a frequency response of 40Hz through 20kHz is a minimum specification to be met.

On the noise spec that rules out popular recorders such as the M-Audio Micro Track II and the Edirol R-09HR. These might prove effective in high dBFS music recording environments but are pretty useless to record in quiet environments.

Two recorders in my view perform particularly well: the Sony PCM-M10 and the Sony PCM-D1.

The PCM-M10 has very quiet omnidirectional built in microphones. Omnidirectional microphones are less sensitive to handling noise (nice to have on a handheld device) and have extended low frequency response.

The PCM-D1 has Analog Devices pre-amps that are virtually noiseless. The microphones are cardioids mounted in an XY coincident pattern. While this would suggest a narrow stereo field Sony managed somehow to overcome this and give recordings made this device a wide stereo image. Might be a device that is hard to find these days as it seems to have been discontinued in some countries in favor of the PCM-D50.

The microphones on both recorders are high sensitivity so dealing with quiet environments is no problem. The D1 has better high-end response compared to the M10.

Samples of recordings I made:

PCM-M10: JanuarySleet.wav, ThunderandRain.wav

PCM-D1: QuietForestSpringEvening.aif, LakeSide2.wav

Esta casa está sonada sound art festival

March 5 through March 6 the Esta casa está sonada (This house is a sound experience) sound art event takes place in a house in el barrio de Santa Lucia, Maracaibo, Venezuela (UTC -4:30 hours). The event is part of the annual Veleda Santa Lucia art festival. During the festival residents of the Santa Lucia neighborhood make their house available for the exhibition.

One of the houses is transformed into a a space to experience sound: “The sound house will be a space for the transmission and experimentation of sound art during la Velada de Santa Lucia: a family home as a sound container.”

The event features my ‘ResonantAtrium’ sound piece on day two, 11PM local time.