United States Patent |
6,017,302
|
Loos |
January 25, 2000 |
Subliminal acoustic manipulation of nervous systems
Abstract
In human subjects, sensory resonances can be excited by subliminal
atmospheric acoustic pulses that are tuned to the resonance frequency. The 1/2
Hz sensory resonance affects the autonomic nervous system and may cause
relaxation, drowsiness, or sexual excitement, depending on the precise acoustic
frequency near 1/2 Hz used. The effects of the 2.5 Hz resonance include slowing
of certain cortical processes, sleepiness, and disorientation. For these effects
to occur, the acoustic intensity must lie in a certain deeply subliminal range.
Suitable apparatus consists of a portable battery-powered source of weak
subaudio acoustic radiation. The method and apparatus can be used by the general
public as an aid to relaxation, sleep, or sexual arousal, and clinically for the
control and perhaps treatment of insomnia, tremors, epileptic seizures, and
anxiety disorders. There is further application as a nonlethal weapon that can
be used in law enforcement standoff situations, for causing drowsiness and
disorientation in targeted subjects. It is then preferable to use venting
acoustic monopoles in the form of a device that inhales and exhales air with
subaudio frequency.
Inventors: |
Loos; Hendricus G. (3019 Cresta Wy.,
Laguna Beach, CA 92651) |
Appl. No.: |
961907 |
Filed: |
October 31, 1997 |
U.S. Class: |
600/28 |
Intern'l Class: |
A61B 005/00 |
Field of Search: |
600/26-28 128/897,898
|
References Cited [Referenced
By]
U.S. Patent Documents
Primary
Examiner: Gilbert; Samuel
Claims
1. Apparatus for manipulating the nervous system of a subject, the
subject having an ear, comprising:
generator means for generating
voltage pulses;
induction means, connected to the generator means and
responsive to the voltage pulses, for inducing at the ear subliminal atmospheric
acoustic pulses with a pulse frequency less than 15 Hz.
2. The apparatus
according to claim 1, further comprising means for automatically controlling the
voltage pulses.
3. The apparatus according to claim 1, further
comprising means for monitoring the voltage pulses.
4. The apparatus
according to claim 1, for exciting in the subject a sensory resonance that
occurs at a resonance frequency less than 15 Hz, the apparatus further
comprising tuning means for enabling a user to tune the pulse frequency to the
resonance frequency.
5. The apparatus according to claim 4, further
including a casing for containing the generator means, the induction means and
the tuning means.
6. The apparatus according to claim 1, wherein said
induction means comprise:
means for generating in the atmosphere a gas
jet, the latter having a momentum flux; and
modulation means, connected
to the generator means and responsive to said voltage pulses, for pulsing the
momentum flux with a frequency less than 15 Hz;
whereby subaudio
acoustic pulses are induced in the atmosphere.
7. Apparatus for
manipulating the nervous system of a subject, the subject having an ear,
comprising:
generator means for generating voltage pulses;
a
source of gas at a pressure different from the ambient atmospheric pressure;
a conduit having an orifice open to the atmosphere for passing a gaseous
flux;
valve means, connected to the source of gas and the conduit to
control the gaseous flux;
means, connected to the generator means and
responsive to said voltage pulses, for operating the valve means to provide an
oscillation of the gaseous flux with a frequency less than 15 Hz.
8. The
apparatus according to claim 7, further comprising vessel means for smoothing
fluctuations of the gaseous flux caused by fluctuations in the pressure of the
source of gas.
9. A method for manipulating the nervous system of a
subject, the subject having an ear, comprising the steps of:
generating
voltage pulses; and
inducing, in a manner responsive to the voltage
pulses, at the ear subliminal atmospheric acoustic pulses with a pulse frequency
less than 15 Hz.
10. The method according to claim 9, for exciting in
the subject a sensory resonance that occurs at a resonance frequency less than
15 Hz, further comprising the step of tuning the pulse frequency to the
resonance frequency.
11. The method according to claim 9, wherein said
inducing comprises the steps of:
generating in the atmosphere a gas jet,
the latter having a momentum flux; and
modulating the momentum flux in
pulse-wise fashion in a manner responsive to the voltage pulses.
12. The
method according to claim 11, further comprising the step of directing the gas
jet at a material surface.
13. The method according to claim 9, wherein
said inducing comprises the steps of:
generating a gas flow through a
conduit orifice that is open to the atmosphere; and
modulating the gas
flow to produce flow pulsations, in a manner responsive to the voltage pulses.
14. A method for remotely manipulating the nervous system of a subject
in the course of law enforcement in a standoff situation, the subject having an
ear, comprising the steps of:
generating voltage pulses;
generating, in a manner responsive to the voltage pulses, atmospheric
acoustic signals at a plurality of locations remote from the subject for
inducing at the ear subliminal atmospheric acoustic pulses with a pulse
frequency less than 15 Hz, the signals having phase differences with respect to
each other arranged to cause constructive acoustic wave interference at the
subject.
15. A method for exciting in a subject a sensory resonance
having a resonance frequency less than 15 Hz, the subject having an ear,
comprising the steps of:
generating voltage pulses;
inducing, in
a manner responsive to the voltage pulses, at the ear subliminal atmospheric
acoustic pulses with a pulse frequency less than 15 Hz;
tuning the pulse
frequency to the resonance frequency; and also
inducing audible
audio-frequency atmospheric acoustic signals at the ear.
16. A method
for controlling in a subject neurological disorders that involve pathological
oscillatory activity of neural circuits, the subject having an ear, comprising
the steps of:
generating voltage pulses;
inducing, in a manner
responsive to the voltage pulses, at the ear subliminal atmospheric acoustic
pulses with a pulse frequency less than 15 Hz; and
arranging said pulse
frequency to detune the pathological oscillatory activity.
17. A method
for controlling in a subject epileptic seizures, the subject having an ear,
comprising the steps of:
generating voltage pulses;
inducing in
a manner responsive to the voltage pulses, at the ear subliminal atmospheric
acoustic pulses with a pulse frequency less than 15 Hz; and
initiating
said inducing when a seizure precursor is felt by the subject.
Description
BACKGROUND OF THE INVENTION
The central nervous system can be
manipulated via sensory pathways. Of interest here is a resonance method wherein
periodic sensory stimulation evokes a physiological response that peaks at
certain stimulus frequencies. This occurs for instance when rocking a baby,
which typically provides relaxation at frequencies near 1/2 Hz. The peaking of
the physiological response versus frequency suggests that one is dealing here
with a resonance mechanism, wherein the periodic sensory signals evoke an
excitation of oscillatory modes in certain neural circuits. The sensory pathway
involved in the rocking example is the vestibular nerve. However, a similar
relaxing response at much the same frequencies can be obtained by gently
stroking a child's hair, or by administering weak heat pulses to the skin, as
discussed in U.S. Pat. No. 5,800,481, Sep. 1, 1998. These three types of
stimulation involve different sensory modalities, but the similarity in
responses and effective frequencies suggests that the resonant neural circuitry
is the same. Apparently, the resonance can be excited either via vestibular
pathways or via cutaneous sensory pathways that carry tactile or temperature
information.
Near 2.5 Hz another sensory resonance has been found that
can be excited by weak heat pulses induced in the skin, as discussed in U.S.
Pat. No. 5,800,481, Sep. 1, 1998. This sensory resonance brings on a slowing of
certain cortical functions, as indicated by a pronounced increase in the time
needed to silently count backward from 100 to 70 with the eyes closed. The
effect is sharply dependent on frequency, as shown by a response peak a mere
0.13 Hz wide. The thermally excited 2.5 Hz resonance was found to also cause
sleepiness, and after long exposure, dizziness and disorientation.
Other, more obscure types of stimulation in the form of weak magnetic
fields or weak external electric fields can also cause the excitation of sensory
resonances, as
SUMMARY OF THE INVENTION
Experiments have shown
that atmospheric acoustic stimulation of deeply subliminal intensity can excite
in a human subject the sensory resonances near 1/2 Hz and 2.5 Hz. The 1/2 Hz
resonance is characterized by ptosis of the eyelids, relaxation, drowsiness, a
tonic smile, tenseness, or sexual excitement, depending on the precise acoustic
frequency near 1/2 Hz that is used. The observable effects of the 2.5 Hz
resonance include a slowing of certain cortical functions, sleepiness, and,
after long exposure, dizziness and disorientation. The finding that these
sensory resonances can be excited by atmospheric acoustic signals of deeply
subliminal intensity opens the way to an apparatus and method for acoustic
manipulation of a subject's nervous system, wherein weak acoustic pulses are
induced in the atmosphere at the subject's ears, and the pulse frequency is
tuned to the resonance frequency of the selected sensory resonance. The method
can be used by the general public for control of insomnia and anxiety, and for
facilitation of relaxation and sexual arousal. Clinical use of the method
includes the control and perhaps a treatment of anxiety disorders, tremors, and
seizures. A suitable embodiment for these applications is a small portable
battery-powered subaudio acoustic radiator which can be tuned to the resonance
frequency of the selected sensory resonance.
There is an embodiment
suitable for law enforcement operations in which a subject's nervous system is
manipulated from a considerable distance, as in a standoff situation. Subliminal
subaudio acoustic pulses at the subject's location may then be induced by
acoustic waves radiating from a venting acoustic monopole, or by a pulsed air
jet, especially when aimed at the subject or at another material surface, where
the jet velocity fluctuations are wholly or partly converted into static
pressure fluctuations.
The described physiological effects occur only if
the intensity of the acoustic stimulation falls in a certain range, called the
effective intensity window. This window has been measured in exploratory fashion
for the 2.5 Hz resonance.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG.
1 illustrates a preferred embodiment wherein a modulated air jet is used for
inducing subliminal acoustic pulses in the atmosphere at the subject's ears, for
the purpose of manipulating the subject's nervous system.
FIG. 2 shows
an embodiment in which a pulsed air jet is produced by modulating the flow from
a fan by a cylindrical sheet valve that is driven by a voice coil.
FIG.
3 shows schematically an acoustic monopole operated by a solenoid valve.
FIG. 4 shows the circuit of a simple generator for producing voltage
pulses that drive a piezoelectric speaker.
FIG. 5 depicts a portable
battery-powered device that contains the circuit and the piezoelectric speaker
of FIG. 4.
FIG. 6 shows schematically a generator for chaotic pulses.
FIG. 7 depicts a circuit for generating a complex wave.
FIG. 8
illustrates an application in a law enforcement standoff situation.
FIG.
9 contains experimental data that show excitation of the sensory resonance near
2.5 Hz, and the effective intensity window.
FIG. 10 depicts experimental
data showing that the sensory excitation occurs via the ear canal.
FIG.
11 shows the buildup of the physiological response to the acoustic stimulation.
FIG. 12 shows schematically an acoustic monopole operated by a rotating
valve.
DETAILED DESCRIPTION OF THE INVENTION
It has been found
in our laboratory that deeply subliminal atmospheric acoustic pulses with
frequency near 1/2 Hz can evoke in a human subject a nervous system response
that includes ptosis of the eyelids, relaxation, drowsiness, the feeling of
pressure at a centered spot on the brow, seeing moving patterns of dark purple
and greenish yellow with the eyes closed, a soft warm feeling in the stomach, a
tonic smile, a "knot" in the stomach, sudden loose stool, and sexual excitement,
depending on the precise acoustic frequency used. These responses show that this
sensory resonance involves the autonomic nervous system.
The sharp
peaking of the physiological effects with frequency is suggestive of a resonance
mechanism, wherein the acoustic stimulation, although subliminal, causes
excitation of a resonance in certain neural circuits. Since the frequencies and
responses are similar to those for the 1/2 Hz sensory resonance discussed in the
Background Section, it appears that the resonance excited by the described
acoustic stimulation is indeed the 1/2 Hz sensory resonance. It has been found
that the 2.5 Hz sensory resonance can be excited acoustically as well. This
sensory resonance causes the slowing of certain cortical processes, sleepiness,
and eventually dizziness and disorientation.
One can avoid the described
physiological responses by wearing snugly fitting ear plugs. This shows that the
excitation occurs via the external ear canal, so that the stimulation proceeds
either through the auditory nerve or the vestibular nerve. Frequencies near 1/2
Hz or 2.5 Hz are far too low for stimulating the cochlear apparatus, but they
are within the response range of hair cells in the vestibular end organ. Also,
there exists a low-frequency acoustic path to the vestibular end organ by virtue
of the ductus reuniens which provides a fluid connection between the cochlea and
the vestibular organ. The narrow duct severely attenuates acoustic signals and
acts as a low pass filter with a very low cutoff frequency. Subaudio acoustic
signals, i.e., acoustic signals with frequencies up to 15 Hz, may perhaps
penetrate to the vestibular organ with sufficient strength for stimulating the
exquisitely sensitive vestibular hair cells.
For the 1/2 Hz and 2.5 Hz
resonances, the described physiological responses are observed only if the
acoustic intensity lies in a certain interval, called the effective intensity
window. The acoustic intensity levels in this window are far below the human
auditory threshold, so that exposed subjects do not sense the acoustic pulses in
any other way than through the mentioned physiological effects. The upper limit
of the effective intensity window is believed to be due to nuisance-guarding
neural circuitry that blocks repeditive nuisance signals from higher processing.
The acoustic signals used for the excitation of sensory resonances have
the nature of pulses. The pulses may be square, trapezoid, or triangle, or
rounded versions of these shapes. However, depending on the pulse frequency,
strong harmonics with frequencies in the audible range could stimulate the
cochlear apparatus. This may be avoided by using sine waves or appropriately
rounded other waves with low harmonic content.
The acoustic pulses occur
in the atmosphere air; even when administered with earphones, the pulses at the
subject's ear constitute pressure and flow pulses in the local atmospheric air.
The resonance frequencies of the 1/2 Hz and 2.5 Hz sensory resonances
lie respectively near 1/2 and 2.5 Hz. The different physiological effects
mentioned occur at slightly different frequencies. Thus, one can tune for
drowsiness or sexual excitement, as desired. The precise resonance frequency is
also expected to depend slightly on the subject and the state of the nervous and
endocrine systems, but it can be measured readily by tuning the acoustic pulse
frequency for maximum physiological effect. Besides the resonances near 1/2 and
2.5 Hz, other sensory resonances may perhaps be found, and those with resonance
frequencies below 15 Hz are expected to be excitable acoustically via the
vestibular nerve, since the vestibular hair cells are sensitive in this
frequency range.
The finding that deeply subliminal subaudio acoustic
stimulation can influence the central nervous system suggests a method and
apparatus for manipulating the nervous system of a subject by inducing
subliminal atmospheric acoustic pulses of subaudio frequency at the subject's
ears. In doing so, one may in addition exploit the sensory resonance mechanism,
but there are important applications where this is not done. For example, the
subliminal acoustic manipulation of the nervous system may be used clinically
for the control of tremors and seizures, by detuning the pathological
oscillatory activity of neural circuits that occurs in these disorders. This may
be done by choosing an acoustic frequency that is slightly different from the
frequency of the pathological oscillation. The evoked neural signals then cause
phase shifts which may diminish or quench the oscillation. Exploitation of the
resonance mechanism by tuning the acoustic signals to the resonance frequency of
a selected sensory resonance affords other forms of manipulation, such as
control of insomnia and anxiety, or facilitation of sexual arousal.
For
both types of manipulation, the required subliminal subaudio acoustic pulses may
be induced at one or both of the subject's ears by earphones with a proper
low-frequency response, acoustic waves generated by an acoustic source and
propagated through the atmosphere, or by a pulsed jet of gas (which may be air),
preferably directed at a material surface open to the atmosphere, such as a wall
or the subject's skin or clothing. In the area of impact, especially where the
surface is oriented substantially perpendicular to the jet, atmospheric pressure
pulses are then generated by virtue of the ram effect, wherein flow velocity
fluctuations are wholly or partly converted into static pressure fluctuations.
If the material surface on which the jet impinges includes the subject's ears,
then these pressure pulses cause direct stimulation of the subject, but the
pulses also propagate through the atmosphere to the subject's ears by virtue of
acoustic wave propagation along accessible paths.
The induction of
atmospheric acoustic pulses by a pulsed air jet proceeding in the atmosphere and
directed at a subject is shown in FIG. 1, where a blower 1, labeled "FAN",
produces an air jet 2 that is directed at a subject 3. The fan is powered by a
power supply 4, labelled "SUPPLY". At the fan, the supply voltage is modulated
in pulsed fashion by a relay 5 controlled by the generator 6, labelled
"GENERATOR", through voltage pulses 7 supplied to electromagnet windings 8. A
user can adjust the frequency of the pulses with the tuning control 9. The
pulsing of the voltage supplied to the fan causes the momentum flux 10 of the
air jet to be modulated in a pulsed manner. Upon impinging on a material surface
such as the skin of the subject 3, the pulsed jet induces acoustic pressure
pulses at the ears 11 of the subject. The atmospheric acoustic effect of the jet
is complicated by the fact that the region of the fan inlet undergoes a
fluctuation of static pressure as the result of the modulation of jet momentum
flux. There thus are two distinct acoustic monopoles, one at the fan inlet and
the other in the area of impact of the jet on the material surface. The
monopoles radiate with a phase difference that is determined by the jet
velocity, the modulation frequency, and the distance between fan and impact
area. The resulting sound pressure at the subject's ears can be analyzed with
retarded potentials as discussed for instance by Morse and Feshbach (1953). Even
a jet which does not impinge on a material surface radiates by virtue of the
acoustic monopole at the fan inlet.
When skin of the subject is exposed
to gas flow of the jet, or to the flow of atmospheric air entrained by the jet,
the flow will fluctuate in pulsed fashion, so that a periodic heat flux occurs
by convective transport and evaporation of sweat. The resulting periodic
fluctuation of the skin temperature can excite a sensory resonance, as discussed
in U.S. Pat. No. 5,800,481, Sep. 1, 1998. Hence, the apparatus of FIG. 1 can
cause excitation of a sensory resonance via two separate sensory pathways, viz.,
the vestibular nerve and the afferents from cutaneous temperature receptors. The
strength of the thermal stimulation depends on the skin area and type of skin
exposed to the fluctuating flow. The face is particularly sensitive, especially
the lips. The two-channel excitation of sensory resonances needs further
investigation. In any particular situation, the vestibular channel can be
blocked by using earplugs.
An air jet with pulsed momentum flux can also
be obtained as illustrated in FIG. 2. Shown is a fan 1, labelled "FAN", which
discharges into manifold 12. The air flow in the manifold can be partially
obstructed by a sheet valve 13 in the form of a perforated cylindrical sheet.
The sheet valve carries a voice coil 14 which is situated in the field of a
permanent magnet 15, in the manner of conventional electromagnetic loudspeakers.
When no current flows through the voice coil, the sheet valve is held in
equilibrium position by springs 16. In this position, the perforation 17 in the
sheet is lined up with the flow passage allowing essentially unimpeded flow
through the manifold and out the exit 18, such as to form a jet 19 in the
atmosphere. Sending a current pulse through the voice coil 14 causes the sheet
valve to be displayed in the axial direction, thereby partially obstructing the
air flow through the manifold. Owing to the low inertia of the sheet valve, the
arrangement allows efficient pulse modulation of the jet momentum flux.
A somewhat different modulation system can be obtained with a rotating
cylindrical sheet valve that has one or more holes along its periphery, and
which is adjacent to a stationary cylindrical shroud that has corresponding
holes, so that rotation of the valve causes modulation of the air flow through
the holes. The valve is rotated by a stepper motor driven by voltage pulses. The
latter are obtained from a generator that is controlled by a tuner.
One
can also use direct acoustic wave propagation for inducing the required
atmospheric acoustic pulses. It is then advantageous to employ as the source of
the waves an acoustic monopole, since for these the acoustic pressure does not
fall off as fast with increasing distance as for dipoles. Moreover, at the very
low frequencies involved, acoustic pressure shorting across a conventional
loudspeaker baffle is very severe. A sealed loudspeaker mounted in an airtight
box eliminates this pressure shorting, and radiates acoustic waves with a
relatively large monopole component.
An acoustic monopole may also be
produced by having a source of pressurized gas vent through an orifice into the
atmosphere in a pulsed fashion. The gas may be air. Alternatively, one may have
a source of low-pressure air inhale atmospheric air through an orifice in pulsed
fashion. These actions are easily achieved by an oscillating or rotating valve.
For purposes of discussion it is convenient to introduce the concept of gaseous
flux through the orifice, defined as the integral of the normal flow velocity
component over an imagined surface that tightly caps the orifice, the normal
component being perpendicular to the local surface element, and reckoned
positive if the flow is directed into the ambient atmosphere. The gaseous flux
has the dimension of m.sup.3 /s. For the case with a source of pressurized gas,
the gaseous flux is positive and due to gas venting to the atmosphere. For the
case with a source of vacuum, the gaseous flux is negative and due to
atmospheric air entering the orifice. The strength of the acoustic monopole is
expressed as the amplitude of the gaseous flux fluctuation, amplitude being
defined as half the peak-to-peak variation. The concept of gaseous flux allows a
unified discussion of venting acoustic monopoles that use a source of
pressurized gas or a source of vacuum, or both.
The source of
pressurized air could be a cylinder with pressurized gas, such as a CO.sub.2
cartridge. For personal use, such a cartridge may last a long time because only
very small acoustic monopole strengths are needed for the induction of the
required weak acoustic signals. For long term and long range operation, the
exhaust port of an air pump may serve as a source of pressurized air, and the
intake port could be used as a source of vacuum.
A simple venting
acoustic monopole is shown in FIG. 12, where the source 63 of pressurized gas,
which may be air, is connected to a conduit 69 which has an orifice 65 that is
open to the atmosphere. A rotating valve 66 labelled "VALVE" controls the
gaseous flux through the orifice. The valve is rotated by a stepper motor 67
labelled "MOTOR", driven by voltage pulses from the generator 68 labelled
"GENERATOR". The motor speed is determined by the frequency of the voltage
pulses. This frequency can be selected by the tuner 70, which therefore controls
the frequency of the acoustic pulses emited by the orifice 65. For the simple
orifice shown, boundary layer separation may occur in the outflow, so that the
air pulses emerge in the form of jets. This causes dipole and higher multipole
components in the radiated acoustic field. If desired, such radiation components
can be avoided or diminished by placing a spherically or dome shaped fine mesh
screen over the orifice 65. Instead of holding pressurized gas, the source 63
may hold a vacuum. In either case, the pulsing of the gaseous flux causes
radiation of monopole-type acoustic waves. The source 63 may be replenished by a
pump.
Push-pull operation can be achieved in the manner shown in FIG. 3.
An air pump 20, labelled "PUMP", with flow ports 64, pressurizes the pressure
vessel 21 while drawing a vacuum in the vacuum vessel 22. A valve 23 is operated
by the solenoid 24 such as to alternately admit high and low pressure air to the
conduit 26. The latter vents to the atmosphere through a screen 55 placed across
an orifice 27 that is open to the atmosphere. The valve is controlled by an
oscillator consisting of the solenoid 24, which is connected to the pulse
generator 6, labelled "GENERATOR". The frequency of the electric current pulses
through the solenoid is determined by the setting of the tuning control 9. This
frequency is to be tuned to the resonance frequency of the sensory resonance
that is to be excited. The tuning may be done manually by a user. The conduit 26
is structured as a diffuser in order to avoid boundary layer separation during
the exhaust phase; the screen across the orifice 27 inhibits formation of a jet,
thereby providing more nearly for a monopole type acoustic wave. During the
intake phase the orifice acts as a sink; streamlines 28 of the resulting flow
are illustrated. The vessels 21 and 22 smooth the flow fluctuations through the
orifice that are due to the flow fluctuations through the pump; they are drawn
at a relatively small scale for compactness sake. Instead of the oscillating
valve 23, a rotating valve may be used, driven by a stepper motor powered by
voltage pulses from a generator.
Conventional loudspeakers may be used
as well as the source of acoustic radiation. An example is shown in FIG. 4,
where the piezoelectric transducer 37 is driven by a simple battery-powered
pulse generator built around two RC timers 30 and 31. Timer 30 (Intersil
ICM7555, for instance) is hooked up for astable operation; it produces a square
wave voltage with a frequency determined by capacitor 33 and the potentiometer
32, which serves as a tuner that may be operated by a user. The square wave
voltage at output 34 drives the LED 35, and appears at one of the output
terminals 36, after voltage division by potentiometer 71. The other output is
connected to the negative supply. The output terminals 36 are connected to the
piezoelectric speaker. Automatic shutoff of the voltage that powers the timer 30
at point 38 is provided by a second timer 31, hooked up for monostable
operation. Shutoff occurs after a time interval determined by resistor 39 and
capacitor 40. Timer 31 is powered by a 9 Volt battery 41, via a switch 42.
Optional rounding of the square wave is done by an RC circuit consisting of a
resistor 43 and capacitor 44. An optional airtight enclosure 29 may be used for
the speaker 37, in order to enhance the monopole component of the radiated
acoustic signal. Instead of a piezoelectric speaker one may use an
electromagnetic loudspeaker with a voice coil. Because of the low impedance of
the voice coil, a resistor must then be included in the output circuitry in
order to keep the output currents to low values such as to allow battery
powering of the device. Small voice coil currents are sufficient for the low
acoustic powers required.
Low pulse frequencies can be monitored with
the LED 35 of FIG. 3. The LED blinks on and off with the square wave, and it
doubles as a power indicator. The pulse frequency can be determined by reading a
clock and counting the LED light pulses. For higher frequencies a monitoring LED
can still be used, if it is driven by a signal obtained by frequency division of
the generator signal.
The automatic shutoff described above is an
example for automatic control of the generated voltage; more sophisticated forms
of control involve automatic frequency sequences. A computer that runs a simple
timing program can be used for the generation of all sorts of square waves that
can be made available at a computer port. An economic and compact version of
such arrangement is provided by the Basic Stamp manufactured by Parallax Inc,
Rocklin, Calif., which has an onboard EEPROM that can be programmed for the
automatic control of the generated pulses, such as to provide desired on/off
times, frequency schedules, or chaotic waves. The square waves can be rounded by
RC circuits, and further smoothed by integration and filtering.
A
compact packaging of the device such as shown of FIG. 4 is depicted in FIG. 5
where all circuit parts and the speaker, piezoelectric or voice-coil type, are
contained in a small casing 62. Shown are the speaker 37, labelled "SPEAKER",
driven by the generator 6, labeled "GENERATOR", with tuning control 9, LED 35,
battery 41, and power switch 42. The LED doubles as a mark for the tuning
control dial. With the circuit of FIG. 4, the device draws so little current
that it can be used for several months as a sleeping aid, with a single 9 Volt
battery.
For the purpose of thwarting habituation to the stimulation,
irregular features may be introduced in the pulse train, such as small
short-term variations of frequency of a chaotic or stochastic nature. Such
chaotic or stochastic acoustic pulses can cause excitation of a sensory
resonance, provided that the average pulse frequency is close to the appropriate
sensory resonance frequency. A chaotic square wave can be generated simply by
cross coupling of two timers. FIG. 6 shows such a hookup, where timers 72 and
73, each labeled "TIMER", have their output pins 74 and 75 connected crosswise
to each other's control voltage pins 76 and 77, via resistors 78 and 79. The
control voltage pins 76 and 75 have capacitors 80 and 81 to ground. If the
timers are hooked up for astable operation with slightly different frequencies,
and appropriate values are chosen for the coupling resistors and capacitors, the
output of either timer is a chaotic square wave with an oval attractor. Example
circuit parameters are: R.sub.78 =440K.OMEGA., R.sub.79 =700K.OMEGA., C.sub.80
=4.7 .mu.F, C.sub.81 =4.7 .mu.F, with (RC).sub.72 =0.83 s and (RC).sub.73 =1.1
s. For these parameters, the output 74 of timer 72 is a chaotic square wave with
a power spectrum that has large peaks at 0.46 Hz and 0.59 Hz. The resulting
chaotic wave is suitable for the excitation of the 1/2 Hz resonance.
A
complex wave may be used for the joint excitation of two different sensory
resonances. A simple generator of a complex wave, suitable for the joint
excitation of the 1/2 Hz autonomic resonance and the 2.5 Hz cortical resonance,
is shown in FIG. 7. Timers 82 and 83 are arranged to produce square waves of
frequencies f.sub.1 and f.sub.2 respectively, where f.sub.1 is near 2.5 Hz, and
f.sub.2 is near 1/2 Hz. The outputs 84 and 85 of the timers are connected to the
inputs of an AND gate 86. The output 87 of the AND gate features a square wave
of frequency f.sub.1, amplitude modulated by a square wave of frequency f.sub.2,
as indicated by the pulse train 88.
The very low frequency waves needed
for the acoustic stimulation of the vestibular nerve may also be provided by a
sound system in which weak subaudio pulses are added to audible audio program
material. This may be done in the customary manner way of adding the currents
from these signals at the inverting input of an operational amplifier. The
amplitude of the pulses is chosen such that the strength of the resulting
acoustic pulses lies in the effective intensity window. Experiments in our
laboratory have shown that the presence of audible signals, such as music or
speech, does not interfere with the excitation of sensory resonances.
The invention can also be implemented as a sound tape or CD ROM which
contains audible audio program material together with subliminal subaudio
signals. The recording can be done by mixing the audio and subaudio signals in
the usual manner. In choosing the subaudio signal level, one must compensate for
the poor frequency response of the recorder and the electronics, at the ultra
low subaudio frequencies used.
The pathological oscillatory neural
activity involved in epileptic seizures and Parkinson's disease is influenced by
the chemical milieu of the neural circuitry involved. Since the excitation of a
sensory resonance may cause a shift in chemical milieu, the pathological
oscillatory activity may be influenced by the resonance. Therefore, the acoustic
excitation discussed may be useful for control and perhaps treatment of tremors
and seizures. Frequent use of such control may afford a treatment of the
disorders by virtue of facilitation and classical conditioning.
In this
as well as in the detuning method discussed before, an epileptic patient can
switch on the acoustic stimulation upon sensing a seizure precursor.
Since the autonomic nervous system is influenced by the 1/2 sensory
resonance, the acoustic excitation of the resonance may be used for the control
and perhaps the treatment of anxiety disorders.
The invention can be
embodied as a nonlethal weapon that remotely induces disorientation and other
discomfort in targeted subjects. Large acoustic power can be obtained easily
with acoustic monopoles of the type depicted in FIG. 3 or FIG. 12. If
considerable distance needs to be maintained to the subject, as in a law
enforcement standoff situation illustrated in FIG. 8, several monopoles can be
used, and it then may become important to have phase differences between the
acoustic signals of the individual monopoles arranged in such a manner as to
maximize the amplitude of the resultant acoustic signal at the location 52 of
the subject. Shown are four squad cars 53, each equiped with an acoustic
monopole capable of generating atmospheric pulses of a frequency appropriate for
the excitation of sensory resonances. The relative phases of the emitted pulses
are arranged such as to compensate for differences of acoustic path lengths 54,
such that the pulses arrive at the subject location 52 with substantially the
same phase, resulting in constructive interference of the local acoustic waves.
Such arrangement can be achieved easily by using radio signals between the
monopole units, with the target distances either dialed in manually or measured
automatically with a range finder. The subaudio acoustic signals can easily
penetrate into a house through an open window, a chimney, or a crack under a
closed door.
Some of our experiments on acoustic excitation of sensory
resonances which provide a basis for the present invention will be discussed
presently. Of all the responses to the excitation of the 1/2 Hz resonance,
ptosis of the eyelids stands out for distinctness, ease of detection, and
sensitivity. When voluntary control of the eyelids is relinquished, the eyelid
position is determined by the relative activities of the sympathetic and
parasympathetic nervous systems. There are two ways in which ptosis can be used
as an indicator that the autonomic system is being affected. In the first, the
subject simply relaxes the control over the eyelids, and makes no effort to
correct for any drooping. The more sensitive second method requires the subject
to first close the eyes about half way. While holding this eyelid position, the
eye are rolled upward, while giving up voluntary control of the eyelids. With
the eyeballs turned up, ptosis will decrease the amount of light admitted to the
eyes, and with full ptosis the light is completely cut off. The second method is
very sensitive because the pressure excerted on the eyeballs by partially closed
eyelids increases parasympathetic activity. As a result, the eyelid position
becomes somewhat labile, exhibiting a slight flutter. The labile state is
sensitive to small shifts in the activities of the sympathetic and
parasympathetic systems. The method works best when the subject is lying flat on
the back and is facing a moderately lit blank wall of light color.
The
frequency at which ptosis is at a maximum is called the ptosis frequency. This
frequency depends somewhat on the state of the nervous and endocrine systems,
and it initially undergoes a downward drift, rapid at first and slowing over
time. The ptosis frequency can be followed in its downward drift by manual
frequency tracking aimed at keeping ptosis at a maximum. At a fixed frequency,
the early ptosis can be maintained in approximately steady state by turning the
acoustic stimulation off as soon as the ptosis starts to decrease, after which
the ptosis goes through an increase followed by a decline. The acoustic
stimulation is turned back on as soon as the decline is perceived, and the cycle
is repeated.
At fixed frequencies near 1/2 Hz, the ptosis cycles slowly
up and down with a period ranging upward from about 3 minutes, depending on the
precise acoustic frequency used. The temporal behavior of the ptosis frequency
is found to depend on the acoustic pulse intensity; the drift and cycle
amplitude are smaller near the low end of the effective intensity window. This
suggests that the drift and the cycling of the ptosis frequency is due to
chemical modulation, wherein the chemical milieu of the neural circuits involved
affects the resonance frequency of these circuits, while the milieu itself is
influenced by the resonance in delayed fashion. Pertinent concentrations are
affected by production, diffusion, and reuptake of the substances involved.
Because of the rather long characteristic time of the ptosis frequency shift, as
shown for instance by the cycle period lasting 3 minutes or longer, it is
suspected that diffusion plays a rate-controlling role in the process.
The resonance frequencies for the different components of the 1/2 Hz
sensory resonance have been measured, using acoustic sine waves with a sound
pressure of 2.times.10.sup.-9 N/m.sup.2 at the subject's left ear. Ptosis
reached a steady state at a frequency of 0.545 Hz. Sexual excitement occurred at
two frequencies, 0.530 Hz and 0.597 Hz, respectively below and above the
steady-state ptosis frequency. For frequencies of 0.480 Hz and 0.527 Hz the
subject fell asleep, whereas tenseness was experienced in the range from 0.600
to 0.617 Hz.
The resonance near 2.5 Hz may be detected as a pronounced
increase in the time needed to silently count backward from 100 to 70, with the
eyes closed. The counting is done with the "silent voice" which involves motor
activation of the larynx appropriate to the numbers to be uttered, but without
passage of air or movement of mouth muscles. The motor activation causes a
feedback in the form of a visceral stress sensation in the larynx. Counting with
the silent voice is different from merely thinking of the numbers, which does
not produce a stress sensation, and is not a sensitive detector of the resonant
state. The larynx stress feedback constitutes a visceral input into the brain
and may thus influence the amplitude of the resonance. This unwanted influence
is kept to a minimum by using the count sparingly in experiment runs. Since
counting is a cortical process, the 2.5 Hz resonance is called a cortical
sensory resonance, in distinction with the autonomic resonance that occurs near
1/2 Hz. In addition to affecting the silent counting, the 2.5 Hz resonance is
expected to influence other cortical processes as well. It has also been found
to have a sleep inducing effect. Very long exposures cause dizziness and
disorientation. The frequency of 2.5 Hz raises concerns about kindling of
epileptic seizures; therefore, the general public should not use the 2.5 Hz
resonance unless this concern has been laid to rest through further experiments.
The sensitivity and numerical nature of the silent count makes it a very
suitable detector of the 2.5 Hz sensory resonance. It therefore has been used
for experiments of frequency response and effective intensity window. In these
experiments, rounded square wave acoustic pulses were produced with a frequency
that was slowly diminished by computer, and the subject's 100-70 counting time
was recorded for certain frequencies. The acoustic transducer was a small
loudspeaker mounted in a sealed cabinet such as to provide acoustic monopole
radiation. At fixed frequency, the acoustic monopole strenght in m.sup.3 /s
varies linearly with the voice coil current, with a constant of proportionality
that can be calculated from measured speaker dome excursions for given currents.
The sound pressure level at the entrance of the subject's nearest external ear
canal can be expressed in terms of the acoustic monopole strength and the
distance from the loudspeaker. For each experiment run, the sound pressure level
at the entrance of the subject's external ear canal can thus be calculated from
the measured amplitude of the voice coil current and the pulse frequency. Since
for the subaudio frequencies the distance from the acoustic radiator to the
subject's ear is much smaller than the wavelength of the sound, the near-field
approximation was used in this calculation. The sound pressure level was
expressed in dB relative to the reference sound pressure of 2.times.10.sup.-5
N/m.sup.2. This reference pressure is traditionally used in the context of human
hearing, and it represents about the normal minimum human hearing threshold at
1.8 KHz.
FIG. 9 shows the result of experiment runs at sound pressure
levels of -67, -61, -55, and -49 dB. Plotted are the subject's 100-70 counting
time versus pulse frequency in a narrow range near 2.5 Hz. Resonance is evident
from the sharp peak 57 in the graph for the sound pressure level of -61 dB. The
graphs also reveal the effective intensity window for the stimulation, as can be
seen by comparing the magnitude of the peaks for the different sound pressure
levels. For increasing intensity, the magnitude of the peak first increases but
then decreases, and no significant peak shows up in the graph for the largest
sound pressure of -49 dB; this can be seen better from the insert 58, which
shows the graphs for -67 and -49 dB in a magnified scale. It follows that the
effective intensity window extends approximately from -73 to -49 dB, in terms of
the sound pressure level at the entrance of the subject's external ear canal.
The physiological response to the 2.5 Hz acoustic stimulation can be
avoided by wearing earplugs. FIG. 10 is a plot of the 100-70 counting time
versus acoustic pulse frequency, with and without earplugs. The sound pressure
level at the entrance of the subject's external ear canal was -6 dB for both
runs. Without earplugs the counting time has the peak 59, but no significant
peak is seen in graph 60 for the run in which the subject used earplugs. Two
conclusions can be reached from these results. First, in the experiments the 2.5
Hz resonance is essentially excited acoustically rather than through the
magnetic field induced by the voice coil currents in the loudspeaker. Second, it
follows that the exciting sound essentially propagates via the external ear
canal, instead of through the skin and bones in the area of the ears, or via
cutaneous mechanoreceptors in the skin at large.
To answer the question
whether the acoustic excitation of the 2.5 Hz sensory resonance occurs perhaps
through the cochlear nerve, one needs to consider the human auditory threshold
curve such as shown, for instance, by Thomson (1967). The curve has a minimum
near 1.8 KHz where the threshold sound pressure level is 0 dB, by definition. At
10 Hz the threshold is 105 dB. Hence, the pronounced acoustic excitation of the
sensory resonance shown in FIG. 9 for a sound pressure level of -61 dB is 166 dB
below the auditory threshold at 10 Hz. The excitation occurs near 2.5 Hz, and at
that frequency, the auditory threshold is even higher than at 10 Hz. Although
the curve in Thomson's book does not go below 10 Hz, linear extrapolation
suggests the estimate of 135 dB for the threshold at 2.5 Hz, bringing the sound
pressure level that is effective for acoustic excitation of the sensory
resonance to 196 dB below the estimated threshold at the frequency near 2.5 Hz
used. This result all but rules out excitation via the cochlear nerve.
Chemical modulation may be the cause for the small frequency difference
for peaks 57 and 59 in FIGS. 9 and 10, for the sound pressure level of -61 dB;
these peaks occur respectively at 2.516 and 2.553 Hz.
The physiological
response to the excitation of the sensory resonances at a fixed stimulus
frequency is not immediate but builds over time. An example is shown in FIG. 11,
where the graph 61 depicts the measured 100-70 time plotted versus elapsed time,
upon application of acoustic pulses of 2.558 Hz frequency and a sound pressure
level of -61 dB. The graph shows that the response is initially delayed over
about 5 minutes; thereafter it increases, and at about 22 minutes the slope is
seen to decrease somewhat. Other experiments have shown a counting time that
eventually settles on a plateau, or even starts on a decline. Chemical
modulation and habituation could account for these features. The response curve
depends strongly on initial conditions.
The method is expected to be
effective also on certain animals, and applications to animal control are
therefore envisioned. The nervous system of mammals is similar to that of
humans, so that the sensory resonances are expected to exist, albeit with
different frequencies. Accordingly, in the present invention subjects are
mammals.
The described method and apparatus can be used beneficially by
the general public and in clinical work. Unfortunately however, there is the
possibility of mischievous use as well. For instance, with small modifications
the method of FIG. 1 can be employed to imperceptibly modulate the air flow in
air conditioning or heating systems that serve a home, office building, or
embassy, for covert manipulation of the nervous systems of occupants.
The invention is not limited by the embodiments shown in the drawings
and described in the specification, which are given by way of example and not of
limitation, but only in accordance with the scope of the appended claims.
REFERENCES
P. M. Morse and H. Feshbach, METHODS OF THEORETICAL
PHYSICS, McGraw-Hill, New York, 1953
R. F. Thomson, FOUNDATIONS OF
PHYSIOLOGICAL PSYCHOLOGY, Harper & Row, New York 1967
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