An area of contention is becoming prevalent among those who investigate the EVP phenomenon. It has to do with whether or not certain types of sensors or microphones can detect EVP. The disagreement has to do with whether EVP is an acoustic phenomenon or something else. This article addresses that issue.
The short answer is "We don't know". There are some who theorize EVP is the result of an EM Field. They claim that the only type of microphone that can pick up EVP is a dynamic or inductive type. While these certainly can pick up EVPs, in order for that claim to be the case one would have to rule out all EVPs which originate from other sources. Clearly valid EVPs have been picked up in other ways, so we must consider EVPs may not always be associated with EM Fields.
Why do they make this claim?
The argument against any acoustic origin of an EVP is that the source is a spirit, and spirits lack any physical body or larynx. Sound, they argue correctly, is the result of air pressure waves. They say that since the spirit lacks a physical body it also lacks any way to place the air in motion.
But stop for a minute. Let's assume for discussion they are correct that since a spirit has no physical body it is unable to interact with air. Yet these same people will claim that a spirit can hear us when we speak. They will attempt verbal communication. But then, how does a spirit, lacking a physical body, hear us? They also don't have an eardrum so how do they hear the air pressure waves we generate by speaking? Sound is air movement and pressure whether spoken or heard. So do spirits interact with air or not? We can't have it both ways.
Another consideration is that there are alternate ways to put air in motion that do not require a physical body. An ionization boundry is one method. While of course that raises the issue of how might a spirit create such a boundry, it also demonstrates that other methods besides a physical body can produce sound. The easiest way to demonstrate such a boundry is with the Flame Speaker experiment. That is where the output of an audio amplifier is connected to two probes in a candle flame and music is played through the amplifier. The flame itself will produce the sound of the music. And of course the flame is not a physical body.
Is there any evidence against the EMF / EVP theory?
I have conducted experiments using various methods of reception in different combinations. One experiment which obtained an EVP used two microphones side by side. One microphone was an electret condenser mic, the other an inductive dynamic type. Both were fed into identical amplifiers and on to a dual channel recorder. Gain and passband settings were the same on both channels. Over multiple attempts several possible EVPs were detected, however crital evaluation was unable to validate most of them. One in particular though did meet the standards to be declared a probable valid EVP. It was heard on both microphones at the same time. If the EMF theory were correct the electret element should have failed to pick it up since they lack any inductive capability. In fact though the signal level from the electret mic. was 6 db higher than that from the dynamic mic. Based on this, at the current state of research it appears that all detection methods are still in play, and more research is required to determine the true nature of an EVP.
So What do you recommend?
I currently use four detection methods for EVPs. They have been used in various combinations at different times to attempt to pick up EVP based on different types of source. I currently recommend that those who study EVP utilize each and compile their own success ratio for each. Below I have outlined each, along with a bit about its benefits and problems as well as my success or failure with them.
Electret / Condenser microphone. This is probably the most common type used today. The overall quality ranges from cheap to high end. They are generally immune to inductive or magnetic signals. Interference from stray RF fields is unlikely provided the cable is properly shielded. They have a wide frequency response and easily cover the entire audio frequency spectrum. They do require a source of phantom power so unless your amplifier is designed to provide this, or your electret mic contains its own internal battery, they will not work.
Electret Mics consist of two plates with a DC potential across them. One is fixed, the other consists of the diaphragm. Sound pressure causes the diaphragm plate to move in response and varies the capacitance between them thus creating an audio signal. Most are enclosed in a metal shield so stray EM Fields are usually blocked. It is said if you utilize one of these you will get only Audio Voice Phenomena.
But will you? Physically, how large is a spirit? How close to the electret element might it get? For sake of discussion let's assume a spirit is very small in size. Now suppose this spirit is able to pass through the case of an electret mic element and position itself near the diaphragm of the microphone. The spirit varies its charge in a voice pattern, electrostatic in nature. This could definitely cause the microphone to respond to changes in the charge level, and if the changes were voice modulated an EVP would be picked up. And if you are recording in stereo using two mics it is evident the spirit only would be in one or the other. As such the EVP would only be on one channel, not both. Of course this is only hypothetical, but it does raise a possible explanation that may cast doubt on the theory that an electret mic cannot pick up EVP.
Inductive / Dynamic microphone. These are generally high end mics and are used by those doing quality work. They are however susceptible to magnetic fields which may compromise the enclosure on all but the high quality ones. Interference from stray RF fields is unlikely provided the cable is properly shielded. They have a wide frequency response and generally cover the entire audio spectrum. No source of phantom power is required.
Many say these are the only type that can be used for EVP work. They are capable of picking up both audio and EM Fields as EVPs. Audio is generated in the normal manner and any EM Field that interacts with the coil may also cause a response. But notice, they do not respond to an electrostatic field since there is no DC potential nor capacitance involved. Since the reach of a magnetic field can extend some distance from the source, it is claimed that inductive microphones might pick up EVP some distance away, over a greater range than the capacitive effect noted in the electret microphone. This neglects to take into consideration the internal shielding of these mics though, and in reality, while still present, the likelyhood of such EM Field interference is very low. If two mics are used in stereo, and both are near each other , it is probable both will be about the same audio level if the source was acoustic. If it was an EM Field the levels may differ considerably depending on distance from the source and mic orientation.
Inductive pickup. A third method is similar to the inductive microphone only without the diaphragm. The inductive pickup consists of simply a coil of wire, sometimes wound over a ferromagnetic core. Any EM Field that interacts with this will generate a signal. If this field contains speech patterns the output signal will consist of this speech. In a stereo configuration both inductors should detect the signal although one may be stronger than the other based on distance from the source and positioning of the coils.
Since there is no diaphragm his type of sensor is immune to any audio signal; Anything detected consists of only EVP, not AVP. As such this can tell us something about the source when it is utilized. It should also be pointed out though that one drawback to using these is that they do have a susceptibility to stray Radio Frequency signals. They may act as an antenna for these signals unless steps are taken to use low pass filters to block any RF.
Electrostatic Field detector. This type of detector will pick up any EVP which may originate via an electrostatic charge or voltage field. By nature it is very susceptible to stray RF therefore provisions must be made to provide a bandpass filter to block undesired signals. They are immune any acoustic audio or sound which is helpful to rule out conventional audio as a source of EVP. There are actually two types of these currently under test. The first uses a very high impedance input and a single ended input J-Fet amplifier. Phantom power is required. This has the advantage of simplicity but is also the least credible due to its propensity for outside interference. An improvement uses three screens positioned near each other. The two outside screens are connected to a differential input amplifier, the center one to a positive DC source with a bypass filter to ground. The amplifier is a high impedance differential type which provides excellent common mode rejection. Any static fields will upset the charge balance between the plates and provide a signal. Of the four methods the electrostatic is the least dependable due to the possibility of false positives caused by static electricity in the air, but when used in conjunction with one of the other methods it can become a way of validating the relationship between electrostatic fields and an EVP.
Photonic Detector While I do not currently use this method it does have merit for exploring the theory that a spirit can generate visible light. If it is possible for a spirit to modulate this visible light, or even UV / IR with speech patterns, this detector would allow us to hear them. A detector for this type of signal would consist of a phototransistor properly shielded against EMF and connected to the input of a high gain amplifier. As such any modulation of the light intensity would be detected and the audio amplified. A spirit could communicate in this manner, and as such, since electronics is involved would also be considered EVP. This detector would be immune to Audio Phenomena, and if properly shielded also EMF and ESF.
And what does all this mean to us who search for EVP?
Several things. First we may need to reconsider exactly what is responsible for an EVP. The popular theory of course is spirit communication. But how do we know that? What proof do we have that spirits even exist in this plane? Maybe we are dealing with something totally different. Consider, what if we are communicating with a living interdimensional entity? Maybe no one who has died at all. Suppose a portal opens allowing actual sound to come through instead of an EM Field. If that is the case the argument for the lack of a larynx falls through. These entities may well have physical being, quite capable of speaking, just in a different dimension.
Or suppose an EM Field is responsible. It is true that an EM Field cannot be heard. But it could well interact with something physical and create sound as a byproduct. This happens regularly in any loudspeaker. What if an EM Field caused a wire in a wall to resonate? Sound results. And while the eletrostatic detectors have only been marginally successful, it still is a viable means of communication. Perhaps some refinement in the methodology may improve their validity. Or maybe someone reading this has an idea for a completely different form of sensor. If so, drop a note and we'll see if we can develop it!
Perhaps there is no one answer. What if the term EVP is in reality a summary of several different types of communication? Maybe some EVPs are acoustic, others electromagnetic, and still others electrostatic in nature. If that were the case then no single method would be effective in all cases. The investigator may need to try multiple methods on each case to determine the most reliable. This actually the approach I am taking currently. I use multiple sensors recording into a multitrack recorder system. My results are currently being evaluated. Sometimes acoustic methods seem better, other times electromagnetic. And at times both are effective, other times neither. This is an area where more research is definitely needed.