Dynamic vs Electret Microphones

The following unique recorded event was captured on 2/20/2013, during an experimental audio recording session. This session was supposed to be a comparative experiment session deploying a dynamic microphone which is jacked in into a Sony IC digital audio recorder using and ART pre-amp; then compared with another Sony digital audio recorder, that is using only its stock electret condenser microphone. The set up was on a table in a small room within a building where all occupants were cleared out, and all lighting sources along with electrical appliances in the room turned off. The synthetic voice was played by a battery operated  MP3 player and speaker system. Before we get to those recordings, lets cover the basics of what was used here.

THE TYPES OF MICROPHONES USED.

(Text Source Wikipedia) Dynamic microphones work via electromagnetic induction. They are robust, relatively inexpensive and resistant to moisture. This, coupled with their potentially high gain before feedback, makes them ideal for on-stage use. Moving-coil microphones use the same dynamic principle as in a loudspeaker, only reversed. A small movable induction coil, positioned in the magnetic field of a permanent magnet, is attached to the diaphragm. When sound enters through the windscreen of the microphone, the sound wave moves the diaphragm. When the diaphragm vibrates, the coil moves in the magnetic field, producing a varying current in the coil through electromagnetic induction. A single dynamic membrane does not respond linearly to all audio frequencies.

(Source Wikipedia) An electret microphone is a type of condenser microphone, which eliminates the need for a polarizing power supply by using a permanently charged material. An electret is a stable dielectric material with a permanently embedded static electric charge (which, due to the high resistance and chemical stability of the material, will not decay for hundreds of years). The name comes from electrostatic and magnet; drawing analogy to the formation of a magnet by alignment of magnetic domains in a piece of iron. Electrets are commonly made by first melting a suitable dielectric material such as a plastic or wax that contains polar molecules, and then allowing it to re-solidify in a powerful electrostatic field. The polar molecules of the dielectric align themselves to the direction of the electrostatic field, producing a permanent electrostatic “bias”. Modern electret microphones use PTFE plastic, either in film or solute form, to form the electret. 

ANOMALOUS CAPTURE.

While the intent of this recording session was purely to observe differences in recording qualities… something unusual was caught. If you look closely at the top track in the waveform and spectrogram, there is a flutter of activity after the question is asked. Which to my ears almost sounds like tiny foot steps scampering across a the table where this experiment was occurring. However as you can observe in the waveform and spectrogram imagery of the bottom track; the event occurs only on the dynamic microphone.

If this had been caught on both microphones, I’d be inclined to say it might have actually been a mouse running across the table. Since the recordings are both of comparable audibility without software amplification; I am inclined to say this an event of either an EMF or RF emergence; whether or not this is a natural or paranormal event, is not absolutely provable either way at this point. Could it possibly have come from the mp3 player and speaker used several feet away…  maybe… but in the hour of mp3 player/speaker operation during this session, this is the only location on the files where this occurs… Nor have I seen this kind of event on my other recording sessions I’ve done using similar set ups… So I’ll leave it as anomalous in my books without other evidence.

Is this one experiment conclusive of anything? No… it is interesting, but as with any experiment, it needs to be replicated numerous times, and by people other than myself. So give it a try on your own, and see what you get! 

It is however something of interest for demonstrating that Dynamic Microphones do capture things that electret condenser microphones do not.

Additional experiments for trying to discern EMF Events from acoustic events would be to replace the condenser microphone with an EMF-Probe such as a coil antenna, a commercial probe like a magcheck-95, or even a simple RadioShack inductive phone recording pick up. These items would not record the waveform of a sound event at all, but the waveform pick up of EMF. Controlled experiments would include not using a mp3 player with speaker to play an audio track; but use a broadcast method that pumps out the track questions in emf vs. sound waves. Place this item near the two microphone set up and see which one captures the emf modulations.

When you listen to the files below you will notice that the electret microphone recording has less background noise giving an over all more quiet texture… This may be due to the inherent noise cancelling properties and emf/rf shielding that are built into modern electret condenser microphones/recorders. The Dynamic microphone is subject to pick up the noise floor threshold which is the  emf given off by computers, lighting systems, appliances, remnants of the big bang… etc… etc…

(Text Source Wikipedia) In signal theory, the noise floor is the measure of the signal created from the sum of all the noise sources and unwanted signals within a measurement system, where noise is defined as any signal other than the one being monitored. In radio communication and electronics, this may include thermal noise, blackbody, cosmic noise as well as atmospheric noise from distant thunderstorms and similar and any other unwanted man-made signals, sometimes referred to as incidental noise.

IMAGES AND SOUND FILES

Images can be enlarged by clicking upon them. It is also suggested that you listen to the following files with good quality speakers or set earphones. Do not use noise cancelling earhpones or speakers… they will block out sounds that may be integral in hearing whats on these files.

Comparative Waveform Views; (Top Track) Dynamic Microphone (Bottom Track) Electret Condenser Microphone)

Comparative Spectrogram Views; (Top Track) Dynamic Microphone (Bottom Track) Electret Condenser Microphone)

HERE IS HOW THE TOP TRACK SOUNDS – DYNAMIC MICROPHONE

HERE IS HOW THE BOTTOM TRACK SOUNDS – ELECTRET CONDENSER MICROPHONE

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