{"id":1232,"date":"2010-04-18T17:54:10","date_gmt":"2010-04-19T00:54:10","guid":{"rendered":"https:\/\/noisejockey.net\/blog\/?p=1232"},"modified":"2010-04-18T17:54:10","modified_gmt":"2010-04-19T00:54:10","slug":"ambiences-with-boundary-mics","status":"publish","type":"post","link":"https:\/\/noisejockey.net\/blog\/2010\/04\/18\/ambiences-with-boundary-mics\/","title":{"rendered":"Ambiences with Boundary Mics"},"content":{"rendered":"
\"Boundary

UFO or listening device?<\/p><\/div>\n

I learned a long time ago to share my mistakes with others. It keeps me humble, and reaches two groups of people: Those more experienced than me who can help correct my errors, and those who might not have tread these waters before and who can learn from my experiences.<\/p>\n

Which brings us to today’s post: recording ambiences using a pair of miniature omnidirectional microphones in boundary layer mounts. I learned a ton doing this, but the end results weren’t great. Today we’ll talk about what I accomplished and why it might not have worked out as well as I had hoped.<\/p>\n

After my recent post on urban ambiences<\/a>, I decided to record some fresh ambiences using a pair of DPA 4060 microphones<\/a> using two techniques I hadn’t tried before: spaced-pair stereo<\/em> and boundary-layer microphones<\/em>.<\/p>\n

Spaced-pair stereo<\/a> is a technique that’s based on both relative volume and delay of sound reaching two omni-directional<\/a> microphones several feet apart. This gives the sense of a stereo field. I was recording street-level ambiences from a third story of a building, and settled on about a 12′ distance between the microphones. (There are equilateral-triangle and 3:1 guidelines about intra-mic-and-subject spacing, but I did as best as the local architecture allowed!)<\/p>\n

After recording for a while, I mounted the DPA 4060’s into boundary layer mounts<\/a> (BLM’s) and kept them the same distance apart. Boundary microphones work by taking advantage of the boundary effect<\/a>, wherein sound undergoes natural amplification just a fraction of an inch above a large, solid surface. While certainly not as good as a dedicated boundary mic like a Sanken CUB-01<\/a>, it’s a nice way to start experimenting. So, I popped the 4060’s into the mounts, taped the mounts to my office windows, and got rolling.<\/p>\n

Today’s sound is simply comparing two sets of vehicle pass-by’s, taken from a much longer city-ambience recording. The first is with the standard DPA 4060’s in their foam windscreens and Remote Audio MicroCats<\/a> to eliminate wind noise. The second features the same mics in the same positions, but popped into the boundary layer mounts. For my part, I noticed two major things.<\/p>\n