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Podcasting Hacks
By Jack Herrington
August 2005
More Info

HACK
#16
Podcast in Surround Sound
Use binaural microphones to give your podcast a three-dimensional sound field
[Discuss (0) | Link to this hack]

Podcasting brings listeners into your life. Podcasting with binaural microphones brings listeners into your head. The idea is simple: use two microphones to simulate your ears. The microphones are usually small lavalier omnidirectionals that should sit as close to your ears as possible. Some people have even rewired headphones so that embedded lavaliers sit right on top of their ears. Others have gone as far as to build models of the human head with microphones that sit inside the ear canals.

Ideally, the two microphones will be matched exactly. Enthusiasts will go as far as to request two microphones with sequential serial numbers. Of course, this perfect matching costs money. A matched set starts at around $200 or $300. But cheaper unmatched sets that are suitable for experimentation and podcasting are available in the $30 range.

shows the Low Cost Binaural Set ($75) from Core Sound (http://core-sound.com/), hooked up through its filter and into a Marantz 660 solid-state recorder . The recorder has a left and right XLR input, both of which are tied into the microphones that connect to either side of the glasses right above your ears.

Figure 1. A set of binaural microphones on glasses, attached to a Marantz 660

The signal from the left lavalier goes into the left channel of a stereo recording, and the signal from the right goes into the right channel. The recording must be in stereo, with no mix between the two channels. When you edit these files, apply effects to both channels equally. When you make cuts, be sure to cut from both channels equally.

You can connect the headset to your computer and record that way, just as you would with a standard stereo microphone. This type of recording is best suited for fieldwork, where you can share your world in stereo just as you experience it. You can attach a binaural headset to the line-in of your portable recording unit. If it sounds underpowered, you will need to buy the battery kit that is sold along with the binaural headset.

Because the idea of binaural recordings is to simulate your ears, you need to both record at your ears and play back at your ears. So, use headphones when listening to binaural recordings to get the full stereo effect, with no balance or fade adjustments.

Here are some fun things to do with binaural podcasts:

Soundseeing tours
Round tables

Interview a group of folks and have some seated to your left and others to your right. Your listeners will be able to distinguish guests by their location.

Parties

Go to a party and take in the small talk and conversation happening all around you.

Concerts and sporting events

Binaural recording opens up a world of podcasting opportunities. For a small investment, you can get some binaural microphones, or make your own from instructions on the Web using microphones from RadioShack.


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