Field Report: Binaural Stealth Recording Experiment

2011/09/21

Union Station Great Hall

Train station sound effects

My goal while field recording sound effects for Airborne Sound is to record beyond simple sound clips and capture vivid, evocative sound. My favorite method for accomplishing this is with stealth recording.

While stealth recording the recordist is secretly immersed in an environment. They have the potential to capture sound effects of people and cultures in their most natural, comfortable state.

Hear and download binaural train station sound effects.

Why equipment is important while stealth recording

Equipment plays a vital role while stealth recording:

  • using too much equipment will cause crowds to be self-conscious and unnatural
  • using basic, cheap equipment results in low-quality recordings
  • minimal equipment is key to allow the recordist to react and adapt to situations immediately

Because of these reasons I am always searching for a lighter, high-quality kit.

For a while I used portable recorders. Some that are popular with field recordists are the Zoom H4n and Sony’s PCM D50. These ‘prosumer’ recorders are small and include onboard microphones.

Unfortunately the only advantage these recorders provide is size. They are not useful for the best stealth recordings. The problem is that these microphones or preamps do not deliver the same quality sound as professional microphones and recorders.

A couple of weeks ago I decided to try another stealth recording option: a binaural microphone.

About binaural microphones

What are binaural microphones?

Binaural microphones are designed to record sound the same way our ears hear. Recordings from binaural microphones have the effect of creating a 3D stereo sound effect. The listener must use headphones to get the most from this effect; speaker cross-talk ruins the imaging effect. This doesn’t mean the effects sound poor over monitors, they just aren’t as evocative.

If done properly, binaural recordings are incredibly immersive. Listeners can sense sounds moving throughout the stereo field, placing them deep within the recording. Binaural microphones are typically small.

Based on this, it would seem that binaural microphones would be a perfect match for evocative stealth field recordings. So why wouldn’t stealth recordists use binaural microphones all the time?

Pros and cons on binaural recording

There are valid arguments for and against binaural microphones.

Pros:

  • inconspcuous
  • creates evocative, immersive recordings when heard through headphones
  • compatible with stereo monitors if binaural aspect is not necessary

Cons:

  • headworn binaural microphones can lose stereo image with the slightest head movement
  • consumer jacks – most have minijack connectors
  • poor performance outdoors with wind

The Shoot

Binaural DSM Microphone

I recently dusted off my Sonic Studio DSM 6S/EH binaural microphone. I had shelved this microphone years ago. I remember that the microphone quality was good. One of its selling points was that when worn it would look like walkman headphones. However the strange powering requirements, lack of native pro jacks had relegated it to the closet. For a ~$700 microphone it had some drawbacks:

  • conspicuous frame
  • poor frame construction
  • odd powering requirements

It also had some advantages:

  • decent sound quality, as I recalled
  • would work with a professional recorder when using the Sonic Studios PA-10PFC adapter

I went to Toronto’s central train station, Union Station, and recorded ambiences.

Results



You are welcome to download and use these sound effects in your personal projects as long as you do not redistribute them, even for free.

If you find them useful, please retweet this post and share it with as many people as you can. Also subscribe to our RSS feed or Twitter. This really helps us!

A handful of workers were repairing the departure area. In this construciton sound effect you can hear hammering and some medium distant speech.

This sound clip is the train station’s squeaky baggage claim conveyor belt. I’m standing to the right of it, so you’ll hear the effect veering on the left channel. There’s also some activity in the background.

This next crowd sound effect was recorded in Union Station’s Great Hall, a vast, high-ceilinged area (see the image at the start of this post). This gives an idea of how a mic of this calibre performes in huge spaces with spread out crowd ‘wash’. You can hear a boy wandering and shouting.

This crowd sound effect is in a hall leading into the Great Hall. Pedestrians are passing by with prominent high heels. There are a few faint voices and distant activity.

Some thoughts

Some people point out that the weakest aspect of headworn binaural microphones is how easy the stereo image can be corrupted. This is one reason that binaural mics are best used on dummy heads. Moving your head can alter the image and ruin the recording.

Typically this requires the recordist to remain stock still to get the best recordings. It’s possible that this posture will look unnatural and cause the recordist to become conspicuous. I tried a few tricks to compensate for this and didn’t have a problem with imaging.

I thought the quality of the microphone was fine for capturing ambiences. I found that binaural microphones shine when embedded within an immediate crowd. For me they gradually lose their sparkle when the crowd is medium distant or further.

I found that I prefer more depth and width to the recordings. The construction sound clip above gives a decent impression of depth and space. It wasn’t a match however for the depth produced by my Neumann RSM 191-i.

Admittedly, comparing the DSM to the 191 or other high end microphones isn’t quite fair. Binaural microphones perform a different role.

As a stealth recording microphone it is a decent option if a more conspicious microphone would compromise a recording. If the situation would allow for a more noticable microphone without damaging a recording, I would use it.

Notes

Gear Used

  • Sonic Studios DSM 6S/EH
  • Sonic Studios PA-10PFC
  • Sound Devices MixPre
  • Sound Devices 722

Links





To stay in touch, receive free updates by email newsletter or RSS feed.  |  Follow on Twitter, Facebook, YouTube, or SoundCloud.

4 responses to Field Report: Binaural Stealth Recording Experiment

  1. The Train Station Crowd Sound Effect sounds like the old days of the Cleveland Terminal — after most of the trains were gone. The separation of the little boy from the crowd as he moves away from the recorder is nice.

    It’s too bad that the new, small still/video cameras have such crappy analog audio performance as they would make good stealth recorders. I am able to get good quality video “street photos” and videos with mine.

    • Thanks, Speed. Those old stations have a great feel to them.

      A video camera is a great idea. Makes me wonder if there is some way to adapt the frame to accommodate a higher-calibre microphone.

      Sort of what Sonic Fields did in his post here:
      http://audiofieldrecordings.wordpress.com/2011/08/25/raw-street-recording-a-near-coincident-spectacle/

      • My experience is limited to the Canon 5D MkII which is too big for stealth but people don’t get too excited if it’s just hanging around your neck or sitting in your lap.

        “But the BIG story is audio. The 5D Mark II gets a sampling bump from 44.1KHz to the more professional 48KHz. And — drum roll, please — you can manually set your recording levels with an on-screen sound meter. Plug in a stereo mic or receiver. You’ll get a visual representation of both left and right channels. Tweak your audio levels as needed, and enjoy pro-grade stereo sound — in camera. If you’re a solo documentarian or indie filmmaker, this is a killer new feature.”
        http://photography.bhinsights.com/content/canon-eos-5d-mark-ii-reborn.html
        http://pro-audio.bhinsights.com/content/mic-shockmounts-canon-5d-mark-ii.html

        More stealthy is the Sony NEX series. I have some experience with the NEX-5 using the built in stereo microphones — not real good. Lots of wind noise and automatic gain control. Stereo separation is surprisingly good for two holes on the top of the camera body. An external mic is an option.

        • I’ll have to try this option for stealth… I’m interested in comparing the preamp quality and stereo image of these units.

          Thanks for the suggestions and links.