A binaural recording is designed to mimic as closely as possible the experience of listening through human ears, and thus binaural microphones are often shaped like the human head with the microphone cartridges placed where the ears would be. That’s not the only way to make a binaural microphone though, and the Crown Stereo Ambient Sampling System, or SASS, did the same thing with a pair of pressure zone microphones for outdoor recordings. [Filip Mulier] doesn’t have one of the originals, but he’s done his best to make a SASS-like microphone of his own.
The attractive thing about this design is its simplicity, making use of foam sheets for the main body, with packing board as a rain deflector and a couple of layers of non-woven cloth as a wind filter. Perhaps best of all though are the recordings, in which we hear ambient recording at its finest. Listen with headphones, we suggest the dawn chorus.
In our occasional series charting audio and Hi-Fi technology we have passed at a technical level the main components of a home audio set-up. In our last outing when we looked at cabling we left you with a promise of covering instrumentation, but now it’s time instead for a short digression into another topic: stereo. It’s a word so tied-in with Hi-Fi that “a stereo” is an alternative word for almost any music system, but what does it really mean? What makes a stereo recording, and how does it arrive at your ears?
From West London Trains, To 3D Audio
As most of you will know, a mono recording uses a single microphone and a single channel while a stereo one uses two microphones recording simultaneously a left and right channel. These are then played back through a pair of speakers, and the result is a sense of spatial field for the listener. Instruments appear to come from their relative positions when recorded, and the sense of being in the performance is enhanced.
Stereo recording as we know it was first perfected as one of the many inventions credited to Alan Blumlein, then working for EMI in London. We have one of his stereo demonstration films in “Trains at Hayes“, filmed from the EMI laboratories overlooking the Great Western Railway, and featuring a series of steam-hauled trains crossing the field of view with a corresponding stereo sound field. His work laid down the fundamentals of stereo recording, including microphone configurations and what would become the standard for stereo audio recording on disk with the channels on the opposite sides of a 45 degree groove. Continue reading “Know Audio: Stereo”→
You don’t have two ears by accident. [Stoppi] has a great post about this, along with a video you can see below. (The text is in German, but that’s what translation is for.) The point to having two ears is that you receive audio information from slightly different angles and distances in each ear and your amazing brain can deduce a lot of spatial information from that data.
For the Arduino demonstration, cheap microphone boards take the place of your ears. A servo motor points to the direction of sound. This would be a good gimmick for a Halloween prop or a noise-sensitive security camera.
We humans may not have superpowers, but the sensor suite we have is still pretty impressive. We have binocular vision that autofocuses and can detect a single photon, skin studded with sensors for touch, heat, and pain, and a sense of smell that can detect chemicals down to the parts per trillion range. Our sense of hearing is pretty powerful, too, allowing us to not only hear sounds over a 140 dB range, but also to locate its source with a fair degree of precision, thanks to the pair of ears on our heads.
Attached to the sides of the foam head once it got the [Van Gogh] treatment, the ears funnel sound to tiny electret cartridge microphones. [Leo] learned the hard way that these little capsule mics can’t use the 48-volt phantom power that’s traditionally pumped up the cable to studio microphones; he fixed that problem with a resistor in parallel with the mic leads. A filtering capacitor, an RC network between the cold line and ground on the balanced audio line, and a shield cleverly fashioned from desoldering braid took care of the RF noise problem.
The video after the break shows the build and test results, which are pretty convincing with headphones on. If you want to build your own but need to learn more about balanced audio and phantom power, we’ve got a short primer on the topic that might help.
[Matt] likes to make videos (and he’s pretty good at it judging by the quality of his videos). But video isn’t much without audio. Handheld recorders with small built-in microphones have a fairly high noise floor so [Matt] has a Rode NT1-A — a pricey but very quiet microphone. However, for field work, it isn’t handy since it requires a power supply and preamp to go along with it.
Another problem is that for stereo recording you need two and because they are quiet, they tend to pick up handling noise so you probably need to mount them on tripods. That’s all too much to carry around, especially on a hike. So [Matt] cannibalized two microphones. He repackaged them in a shock mount (made from a bird feeder and elastic), and added a battery pack and a custom preamp. The shock mount eliminates the handling noise and the custom PC boards mean you don’t have to carry a lot of extra gear.
The end result (see the video below) looks like someone made a purse out of a tribble, but it does sound good. If you hang on through most of the video (of fast forward to about 7:25), you can hear the microphones picking up thunderstorms, the ocean, the wind, and even [Matt’s] heartbeat.
Binaural audio is probably the coolest thing you can listen to with a pair of headphones. Instead of just a single microphone, binaural recordings use two microphones, set inside an analog for a human head, to replicate exactly what you would hear if you were there.
The only way to record binaural audio is with fake plastic ears attached to a dummy head. Most of the famous microphone manufacturers have something like this, but with a 3D printer, anything is possible. [Carlos] created his own binaural microphone using a 3D printer and went through the trouble of creating a few audio demos. The results are weird, like [Carlos] is whispering into your ear.
The ears used in this microphone setup are taken from a Thingiverse project by [Jonathan March]. This model did not properly model the ear canal,and didn’t have any way to mask the sound from ear to ear; this is why the professional models also include a head. [Carlos] fixed these shortcomings and created a few 3D models that accurately model the human ear and head.
There’s also a simple stereo microphone amplifier for this project that is designed to fit right between the ears. This amplifier was designed in KiCAD, and the PCB is single sided. It’s not quite simple enough to assemble on a piece of stripboard, but [Carlos] did manage to manufacture it on some copper clad board in his mill.
The results? It sounds awesome. [Carlos] put together a demo of his microphone, link below, and it only works if you’re wearing headphones.
Aiming to be the leader in Virtual Reality horror experiences is the immersive VR haunted house in Seattle called ‘The Nightmare Machine’ which promises to be one of the most terrifying events this Halloween. But they need some assistance raising money to achieve the type of scale on a large public level that the project is attempting. The goal is $70,000 within a 30 day period which is quite the challenge, and the team will need to hustle every single day in order to accomplish it.
Yet the focus of the project looks good though, which is to lower the massive barriers of entry in VR that are associated with high hardware costs and provide people with a terrifying 5 minutes of nightmare-inducing experiences. This type of fidelity and range is usually only seen in military research facilities and university labs, like the MxR Lab at USC. And, their custom-built head mounted displays bring out this technology into the reach of the public ready to scare the pants off of anyone willing to put on the VR goggles.
The headsets are completely wireless, multi-player and contain immersive binaural audio inside. A motion sensing system has also been integrated that can track movements of the users within hundreds of square feet. Their platform is a combination of custom in-house and 3rd party hardware along with a slick software framework. The technology looks amazing, and the prizes given out through the Kickstarter are cool too! For example, anyone who puts in $175 or more gets to have their head 3D scanned and inserted into the Nightmare Machine. The rest of the prices include tickets to the October showcase where demos of the VR experience will be shown.