Snoring suppression system

An adaptive snoring signal suppression system globally cancels snoring signals by determining a canceling signal based on a received snoring signal. The system creates a doublet between a plane of a speaker and the source of the snoring signal such that at the plane of the speaker, the canceling signal is 180 degrees out of phase with the snoring signal as measured at the source. The system uses digital signal processing to adaptively estimate a snoring sound canceling signal based on past snoring signals.

BACKGROUND OF THE INVENTION 
The invention relates generally to apparatus and systems for suppressing 
sounds resultant from snoring and more particularly to systems for 
suppressing sounds produced by snoring wherein the originating snoring 
sounds are substantially suppressed by generating sound canceling signals. 
Many attempts have been made to overcome the problem of snoring for both 
the snoring person and other persons that may hear the snoring sounds. 
Many systems and methods for eliminating the problem of snoring are 
designed to awaken or otherwise interrupt the person generating the 
snoring sounds. For example, some systems activate an alarm based on a 
predetermined loudness level of the snore sensed by a sound sensor. 
Another system includes an eye cover which has an actuating mechanism for 
activating a flashing light so that the snorer is awakened upon sensing of 
snoring sounds. However, such systems unnecessarily wake up a snoring 
person so that the snoring person is deprived of a comfortable rest. 
Other systems which have been developed in an attempt to overcome the 
problem of snoring include air bags which may be mounted to the back of 
the snoring person to prevent the person from lying on their back. This 
may prevent snoring, but may do so at the expense of comfort. Another 
system includes a sling which is worn over the mouth of a person to keep 
the mouth closed so that the wearer is unable to generate a snoring sound. 
These systems unnecessarily restrict the physical comfort of the snoring 
individual so that the snoring individual is forced to sleep in an 
unnatural state. 
Other systems, such as ear plugs for the non-snoring person reduce the 
effects of snoring by attempting to completely block all sounds 
(particularly the snoring sound signal) from reaching an ear drum of the 
non-snoring person. This allows the snoring person to sleep comfortably 
and continue snoring. However, such systems are typically onerous and 
possibly life threatening to the non-snoring person since the non-snoring 
person might be unable to hear other audible signals, such as audible 
smoke alarm or fire alarm warning signals. 
No snoring attenuation systems are known that substantially cancel or 
otherwise attenuate snoring sound signals so that neither the snoring 
person nor another non-snoring person needs to wear an overly restrictive 
or unnecessarily uncomfortable snore prevention system. Although the 
theory of sound cancellation through the use of canceling signals is 
generally known, no snoring sound signal attenuation systems are known 
that use audible canceling signals to suppress snoring sounds. In general, 
audible canceling signals typically have a same amplitude but a phase 
angle that is 180 degrees from that of a source sound signal. 
Known adaptive sound cancellation systems, cancel sounds (noise) at a 
location other than the source of the sound, such as at an opening in a 
duct. Typically, the point at which a cancellation signal is directed 
(cancellation point) is fixed and down stream from the signal source. For 
example, many systems cancel sound at a point downstream from the source 
of a sound such as an opening in a duct so that the control system has 
adequate time to determine a proper cancel signal. Therefore, where the 
noise cancellation point is sufficiently distant from the source of the 
noise, and a sensor is placed at the source and another sensor at the 
cancellation point, the control system may readily calculate and output a 
canceling signal downstream from the source. 
One example is disclosed in European Patent Application 465,174 entitled 
"Adaptive Active Noise Cancellation Apparatus". Such a system uses a 
control system to cancel noise at an opening of a duct. The control system 
uses an adaptive filter for aiding in reducing unwanted noise in ducts. 
However, such known noise cancellation systems typically require the use 
of a plurality of microphones for determining an error signal, and a duct 
for conducting sound (audible) signals so that the sound source signal is 
directionally limited to better facilitate cancellation. 
Such systems, typically determine the error signal by placing a microphone 
at the opening of the duct to determine the level of noise emanating from 
the opening of the duct. Such an error signal may then be input into an 
adaptive filter after being delayed by a predetermined time. A second 
microphone or sensor is typically placed at the source of the noise to 
determine the actual source sound signal. The adaptive filter uses the 
error signal to determine a canceling signal, having the same amplitude 
but a 180 degree phase difference from the error signal emanating at the 
opening of the duct. The output signal is typically output by a signal 
processor through a speaker directed at the duct opening to substantially 
cancel the sound signal at the opening. 
However, such systems are typically limited to reducing noise signals at a 
single stationary point (duct opening) away from the source. Canceling 
signals away from the source gives these types of systems ample time to 
generate and evaluate error signals to better calculate canceling signals. 
In addition, such duct-type systems are typically not adapted to operate 
in an open area, such as a bed room or other room in a house. Such open 
areas may allow the source signal to radiate and propagate in many 
directions unlike the duct arrangement which guides the signals to an 
opening. Furthermore, such duct systems require at least two sensors, one 
for sensing the source sound signal and one for sensing the signal at the 
duct opening to determine an error signal. Also, since the duct opening is 
typically the only point at which noise may be radiated, the control 
system attempts to calculate and output a canceling signal so that the 
canceling signal plane of the duct opening is 180 degrees out of phase 
with respect to the noise signal at the plane of the duct opening. 
Another known noise attenuation system, such as that disclosed in U.S. Pat. 
No. 4,677,676 entitled "Active Attenuation System With On-line Modeling of 
Speaker, Air Path and Feedback Path", also utilizes a duct arrangement. 
Again, such systems do not cancel at the source of the sound signal and 
use an additional microphone located down stream from where the canceling 
signal is output, to determine an error signal. 
Based on the foregoing, known noise canceling systems typically cancel at a 
fixed, nonmoving point, such as an opening in a duct. Therefore, known 
noise canceling systems are typically not suitable wherein the sound to be 
canceled is a moving sound source such as a snoring sound source. 
A problem also arises with such systems where a source may emanate in a 
substantially omnidirectional pattern. Such is the case with a snoring 
individual since snoring sounds are typically emanated in almost an 
omnidirectional pattern in an open room. Furthermore, it would be 
desirable to substantially globally cancel snoring sounds instead of 
attempting to locally cancel a sound at a selected point away from the 
source since the snoring sound may be heard at points other than one fixed 
point. Global reduction of the snoring sound would also be advantageous 
since an individual (the ears of the individual), such as a non-snoring 
spouse, may move throughout the night. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the invention to provide a snoring 
attenuation system that substantially facilitates global suppression of 
snoring sound signals. 
It is another object of the invention to provide a snoring attenuation 
system that substantially facilitates global suppression of snoring sound 
signals by creating a doublet between a canceling sound output device, 
such as a speaker, and the snore signal source, such as a mouth of a 
snoring person wherein the canceling sound output device produces a snore 
cancel signal to cancel at least some of the snore sound signal. 
It is also another object of the present invention to provide a snoring 
attenuation system that facilitates the suppression of snoring sounds 
substantially at the source of the snoring sound signals wherein the 
source may move during output of the snore signal. 
It is an object of the present invention to provide a snoring attenuation 
system that allows the snoring person to sleep in a comfortable position 
and without unnecessary interruption. 
It is yet a further object of the present invention to provide a snoring 
attenuation system that facilitates suppression of snoring sounds 
substantially at the source of the snoring sound signal wherein the system 
includes a tracking mechanism for determining the location of the snoring 
sound source signals to facilitate snore sound cancellation for a moving 
snore signal source. 
It is also an object of the present invention to provide a snoring 
attenuation system that may prevent the output of canceling signals in 
response to an evaluation of a snore source signal. 
It is another object of the present invention to provide a snoring 
attenuation system that facilitates the suppression of snoring sounds by 
outputting a snore cancellation signal from at least one of a plurality of 
speakers wherein the plurality of speakers are selectively activated in 
response to the sensed location of the snoring sound source. 
It is a further object of the invention to provide a snoring attenuation 
system that substantially facilitates global suppression of snoring sound 
signals by creating a doublet between a canceling sound output device, 
such as a speaker, and the snore signal source, such as a mouth of a 
snoring person, wherein the system includes an adaptive filtering 
mechanism for determining and generating a snore canceling signal based on 
an analysis of a current snore signal. 
A snoring suppression system is disclosed which includes a sound receiving 
stage such as a cordless microphone coupled to an A/D circuit. The 
microphone may be located in a mouth piece placed in the mouth of the 
snoring person. A sound transducing device, such as speaker, outputs a 
snore canceling signal toward the snoring sound source to form a doublet 
between the sound transducing device and the snore sound source. A signal 
processor generates the snore canceling signal based on the received snore 
signal, such that the snore canceling signal, as measured at a plane of 
emission of the sound transducing device, has approximately an 180 degree 
phase difference from the snoring signal phase angle and a substantially 
same amplitude as the snoring signal amplitude as measured at the snore 
source or the mouth of snoring person. The system may include a sensing 
mechanism for determining a position of the snore sound source during 
movement of the snore sound source. 
The system may also include a transducer control mechanism for preventing 
the canceling signal from being output by the transducing device when the 
snoring signal, as received by the receiving means, does not conform to 
some type of predetermined signal criteria, such as average signal 
strength or signal correlation parameters. 
The sensing mechanism may include a position sensing mechanism, such as an 
ultrasonic emitter and detector pair, wherein one of either the emitter or 
detector may be suitably affixed to the snore sound source, such as 
affixed in a mouthpiece, and the other component may be suitably affixed 
to the transducing device. The sensing mechanism may then determine the 
location of the snore sound source. The position sensing mechanism has a 
controller for activating or deactivating the transducing device in 
response to an output signal from the position sensor. 
For example, the system may include a multi-speaker select mechanism to 
selectively activate at least one of a plurality of speakers in response 
to the output signal from the position sensing mechanism so that an 
optimum speaker from the plurality of speakers may be selectively 
activated to effectuate suitable snore signal suppression. The system may 
also include a movable transducing device. The sensing mechanism may be 
used to facilitate movement of a speaker coincident with a moving sound 
source to maintain a relative position between the sound transducing 
device and the snore sound to effectuate suitable snore signal 
suppression. 
The digital signal processing stage is adapted to receive a digital signal 
representation of the received snore signal and determines a plurality of 
filter coefficients. The signal processing stage modifies the digital 
signal representation of the snore signal using the coefficients to 
generate a pre-output canceling signal wherein the pre-output canceling 
signal becomes the canceling signal output by the transducing device. The 
digital signal processing stage further includes a filter, such as a fast 
Fourier transform (FFT) filter, for outputting the digital signal 
representation in a plurality of frequency ranges. 
In another embodiment, a second microphone may be positioned to evaluate 
and adjust the suppressing effect of the system. For example, the 
microphone may be located in a headset worn by an adjacent person to 
determine the signal heard by the adjacent person. The system may then 
adjust the canceling signal to optimize suppression of the snore signal. 
A method is disclosed which includes receiving the snoring sound signal 
proximate the snore sound source; outputting a snore canceling signal 
directionally toward the snoring sound source to form the doublet between 
the speaker and the snore sound source; generating the snore canceling 
signal, such that the snore canceling signal, as measured at a plane of 
emission of the speaker, has approximately an 180 degree phase difference 
from the snoring signal phase angle and a substantially same amplitude as 
the snoring signal amplitude as measured at the source of the snore 
signal. 
The method may further include the steps of determining a position of the 
snore sound source during movement of the snore sound source; and 
preventing the canceling signal from being output by the speaker when the 
snoring signal is not within the predetermined signal criteria.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 generally illustrates the creation of a doublet as created by the 
inventive snoring attenuation system for globally reducing snoring 
signals. As shown, a snoring person 1 laying on a bed 2 emits a snore 
source signal 3 from a snore source 4, such as a snorer's mouth. The snore 
source signal 3 has an amplitude, frequency and phase angle associated 
with it. An adjacent person 5 is assumed to be in hearing range of the 
snore source signal 3. 
A cancel signal output device 6, such as a speaker, has a plane 7 and emits 
a snore canceling signal 8 in an opposing direction, along the Y-plane, to 
that of the snore source signal 3. The snore canceling signal 8 as output 
at the plane 7 of the speaker, has a substantially same amplitude and 
frequency, but a phase difference of 180 degrees compared to the snore 
source signal measured at the mouth 4 of the snoring person 1. 
When the speaker 6 and the snore source 4 are close enough to each other, a 
sound source doublet is created between the speaker 6 and the snore sound 
source 4 (mouth) so that the snore sound is substantially suppressed. The 
best snore suppression occurs along a Y.dbd.O plane wherein O is a point 
located midway along a Y-axis between the snore source 4 and the plane 7 
of the speaker and at 90 degrees with respect to the Y-axis. Therefore the 
other person 5, when positioned as indicated, hears less snoring noise due 
to the canceling of the snore sound. As shown by the dashed lines 9, the 
snore source 4 may move as the snoring person 1 turns their head, thereby 
changing the location and orientation of the Y-axis. Consequently it is 
desirable to move the speaker 6 to maintain a doublet that cancels signals 
in the plane(s) coincident with the other persons ear. It will be 
recognized that some form of signal attenuation occurs in planes on either 
side of the Y.dbd.O plane. Consequently, the system provides suppression 
of snoring signals at more than one point, hence the term global 
suppression. 
FIG. 2 schematically depicts a snoring attenuation system 10 in accordance 
with the invention to carry out the doublet effect as generally described 
above. The system 10 includes a snore sound signal receiving stage 12, a 
snore canceling signal generating stage 14, formed from a digital signal 
processor, which receives a current digital snore sound signal x(n) from 
the receiving stage 12, and a sound transducing stage 16 for outputting a 
snore canceling signal as generated by the canceling signal generating 
stage 14. 
The snore signal receiving stage 12 may include a microphone 18 positioned 
adjacent to or in the mouth of a snoring person 1. An amplifier 20 
receives the snore source signal 3 from the microphone 18 and amplifies it 
to a suitable level as known in the art. An output from the amplifier 20 
is converted from an analog signal to a digital signal x(n) through A/D 
converter 22. 
The snore canceling signal generating stage 14 includes a fast Fourier 
transformation (FFT) filter stage 24, an adaptive filter stage 25 and a 
digital filter stage 26. A plurality of delay stages 23a and 23b represent 
the delay incurred in accumulating signal samples for the FFT filter stage 
24 and the adaptive filter stage 25; both of which do not process signals 
in real time. 
The digitized snore signal x(n) also serves as an input to the digital 
filter stage 26 and a speaker control stage 27 as will be described later. 
The FFT filter stage 24 receives the digitized snore signal x(n) and 
accumulates signal samples to carry out an inverse operation using the 
inverse transfer function of the system 10 (which take into account the 
distortion and delays from the various components in system) as known in 
the art. 
In general, the FFT filter stage 24 and the adaptive filter stage 25 
facilitate the determination of fixed (although periodically changed) 
filter coefficients 29 for the digital filter stage 26. In order to 
calculate the filter coefficients 29, an assumption is made that the 
statistics of the snoring signal will be relatively constant over a 
predetermined period of time (e.g. 50 msec, 500 msec or 1000 msec) so that 
the fixed coefficients 29 will remain "fixed" for some predetermined 
period of time but that the coefficients 29 may change from one time 
interval to another in response to the varying snore signal x(n). 
The FFT stage 24 includes an FFT processing stage, a multiplication 
mechanism, and an inverse FFT processing stage. The FFT processing stage 
converts temporal signal data to frequency domain data. The output from 
the FFT processing stage serves an input to the multiplication mechanism. 
The multiplication mechanism modifies the output frequency domain signal 
data by multiplying the frequency domain data by matrix elements that 
represent the inverse transfer function of the system 10. The output from 
the multiplication mechanism serves as the input to the inverse FFT 
processing stage. The inverse FFT processing stage generates a desired 
output signal d(n-t). However, it will be recognized that any suitable 
signal processing technique may also be used instead of the FFT stage 24, 
such as a series of digital filters. 
The desired output signal d(n-t) represents a canceling signal that would 
have canceled a delayed snore signal x(n-t). The desired output signal 
d(n-t) serves as an input to the adaptive filter stage 25. The adaptive 
filter stage 25 determines the filter coefficients 29 necessary to 
generate the proper canceling signal y(n-t) for x(n-t). The digital filter 
applies the coefficients to the snore signal x(n). 
The adaptive filter 25 utilizes the desired cancel signal d(n-t) and the 
delay signal x(n-t) to determine the coefficients required to generate 
d(n-t) from x(n-t). The digital filter 26 receives the digitized snoring 
signal x(n) and modifies the snoring signal x(n) in real time by the fixed 
filter coefficients 29 to produce the corresponding pre-output canceling 
signal y(n). The pre-output cancel signal y(n), derived from x(n), 
corresponds to the signal which, when passed through the stage 16, becomes 
the canceling signal 8. Since the system 10 has internal delays .tau., the 
cancel signal generating stage 14 predicts the snore signal at time .tau. 
after a given sample is taken and generates a corresponding snore cancel 
signal 8. The cancel signal generating stage 14 uses current and previous 
snore signal samples to generate the cancel signal 8. It is assumed that 
the snore signals are predictable for a period of time equal to the delay 
.tau. in the system 10. 
The sound transducing stage 16 converts the generated pre-output canceling 
signal y(n) to an analog signal through the digital to analog converter 
28. The output from the D/A converter 28, is amplified through amplifier 
30. The output from amplifier 30 serves as the input to the sound 
transducer 32, such as a speaker 8 (shown in FIG. 1). 
The speaker controller stage 27 may be a microprocessor or a portion of the 
digital signal processor that forms the canceling signal generating stage 
14 and serves to detect an uncorrelated signal or otherwise anomalous 
signal. The speaker controller stage 27 prevents the sound transducer 32 
from outputting audible sounds in response to predetermined signal 
criteria such as the detection of an undesirable condition. For example, 
where the average amplitude of a snore signal rises or falls below a 
predetermined threshold, audible output to the sound transducer 32 may be 
prevented. Such a condition may arise when unexpected noises are detected 
and can not be canceled until enough samples are obtained by the FFT and 
adaptive filters. 
Also, the speaker controller 27 may prevent signals from being output if 
the snore signal and the canceling signal fail to converge after a 
predetermined time. The speaker controller 27 may also prevent the output 
stage 16 from outputting a signal if a runaway signal is detected, such as 
if x(n) is an undesirable resonating signal. It will be recognized that 
any suitable signal analysis technique may be used such as logarithmic 
correlation techniques or average amplitude sampling techniques. Also, the 
speaker controller 27 may be connected to other control systems such as 
the detection mechanism described with reference to FIG. 4b or may be 
incorporated as part of the detection mechanism. 
Other criteria may also serve as the basis for prohibiting a cancel signal 
from being output. For example, the adaptive filter 25 may determine that 
it is unstable and cease to output coefficients 29. In this case, the 
digital filter 26 may continue to use prior coefficients which in turn 
would affect the pre-output cancel signal. The speaker controller 27 may 
then determine that the cancel signal and the snoring signal do not 
converge and subsequently prohibit the cancel signal from being output. 
Alternatively, the adaptive filter 25 may directly prohibit signal output 
to the speaker. 
FIG. 3a depicts generally a preferred embodiment for the canceling signal 
generating stage 14. It has been found that low frequency snoring signals 
typically have few harmonics. Consequently, lower frequency signals such 
as those between the range of approximately 20 Hz to 120 Hz, allow the 
digital signal processing to be simplified so that fewer samples may be 
taken and analyzed to generate a proper fixed coefficient and suitable 
canceling signal. More particularly, the FFT may use a small portion of 
the transfer function matrix, as known in the art, which reduces the 
complexity of the signal processing. 
The FFT filter stage 24 divides the samples of the current digital signal 
x(n) into a plurality of sample sets corresponding to different frequency 
ranges. For example, signal portion d1 may include signals in the range of 
20-250 Hz, signal portion d2 may include signals in the range of 250-450 
Hz and signal portion d3 may include signals in the range of 450-1000 Hz. 
Each of the adaptive filters 25a-25c may include a prefilter portion which 
includes a constant delay filtering section to filter out the frequencies 
of non-interest from x(n). For example, adaptive filter 25a may have a low 
pass filter to allow the low frequency component of x(n) to be analyzed. A 
sampling rate divider portion in each of the adaptive filters 26a-26c 
allows each respective filter to sample the input signal to each of the 
filters at a selected rate. For example, since lower frequencies need not 
be sampled as often to obtain sufficient information for the signal, the 
adaptive filter 25a may sample one out of every eighth signal element. 
Similarly, adaptive filter 25c may sample every signal element since more 
samples are generally required to analyze higher frequency signals. 
Each of a plurality of adaptive filters 25a-25c are configured to calculate 
filter coefficients 29a, 29b and 29c for one of the frequency ranges. For 
example adaptive filter 25a may be configured to calculate coefficients 
for low frequency ranges (20 Hz-250 Hz) whereas adaptive filter 25c may be 
configured to calculate coefficients for the high frequency ranges 
(450-1000 Hz). Each adaptive filter 25a-25c provides the coefficients 
29a-29c for a corresponding digital filter 26a-26c. The adaptive filters 
25a-25c may employ a least means squares technique, or a recursive least 
squares RLS technique, however, any other suitable filtering technique may 
also be used. 
Digital filters 26a-26c may include a plurality of identical sampling rate 
divider sections to facilitate proper signal sampling of x(n). For 
example, digital filter 26a may have eight identical digital filters in 
parallel wherein one digital filter samples a first signal element, a 
second digital filter samples a second signal element, a third digital 
filter samples a third signal element, etc. Each of the separate digital 
filters uses the same coefficient as received from the adaptive filter 
section 25a. 
The output signal from each of the digital filters 26a-26c is combined 
through a summing circuit 31. The output from the summing circuit 31 
serves as the generated canceling signal y(n) to the sound transducing 
stage 16 (see FIG. 2). 
The system 10 may also include temporarily stored filter coefficients for 
use with different sections of the snoring signal to speed up the 
processing time for generating a pre-output cancel signal. For example, 
the frequencies during inhaling may have corresponding filter coefficients 
stored for initial use by the digital filters 26a-26c, whereafter the 
coefficients may be updated. Similarly, frequencies corresponding to 
exhaling may also have corresponding coefficients stored for initial use 
by the digital filters 26a-26c so that when the system detects exhaling 
signals, the system may initially use the stored coefficients for the 
signal processing steps to generate a suitable cancellation signal. 
FIG. 3b is another embodiment of a canceled signal generating stage that 
may be applicable where the speaker has a high amount of distortion at low 
frequencies. FIG. 3b differs from FIG. 3a in that a sine/cosine generator 
41 is used to represent low frequency components of the signal x(n) for 
adaptive filter 43 and a digital filter 45. The sine/cosine generator 41 
modifies the signal x(n) for low frequencies as determined by an input 
signal portion f1. The input signal portion f1 is a series of frequencies 
from the FFT stage 24 which form the low frequency components of x(n) and 
is therefore indicated as being in the frequency domain. 
The sine/cosine generator 41 produces sine and cosine waveforms that when 
combined form low frequency components of x(n). The sine/cosine generator 
41 generates sine and cosine waveforms which are Eigen-functions of the 
system and may provide phase compensation and amplitude compensation for 
each sine and cosine representation as known in the art. The approach uses 
the fact that there are dominant frequencies and can extrapolate future 
signals using the sine and cosine signals. 
The adaptive filter 43 generates new coefficients 47 which represent the 
contribution of each of the given frequencies that form the low frequency 
component of x(n). The digital filter 45 applies the coefficients 47 to 
the sine/cosine signals output by the sine/cosine generator 41 thereby 
recreating low frequency components of x(n). The digital filter 45 output 
is input to the summing circuit 31, as previously described. The system as 
shown in FIG. 3b allows the system to overcome and compensate for the high 
distortions at low frequencies. It will be recognized that although the 
above embodiment uses a single sine/cosine generator 41 for the low 
frequency portion of x(n), it may be advantageous to represent x(n) 
entirely in the form of sine and cosine components for all frequencies of 
x(n). 
Referring to FIGS. 2-3b, the system 10 generates a canceling signal such 
that the canceling signal as measured at the plane of emission of the 
cancel signal 8 as output by the sound transducer 32 has a substantially 
same amplitude and frequency, but a phase difference of 180 degrees 
compared to the snore source signal measured at the mouth 4 of the snoring 
person 1 (see FIG. 1). It is preferred that the speaker 32 has a limited 
frequency response such as from 20 Hz to 1000 Hz which is the typical 
range of snoring sound frequencies. The speaker 32 may also be designed so 
that its response function approximates a minimum delay that is as 
constant as possible over a frequency range of the snoring signals (20 
Hz-1000 Hz). However, any suitable speaker may be used. 
The microphone 18 may be of the type which has rapidly decreasing 
sensitivity in proportion to its distance from the snore source signal. 
For example, the microphone 18 should not pick up the source sound signal 
if the microphone is moved too far away from a mouth of a snoring person 
20. Since the speaker should be further from the mouth than the 
microphone, the effect of the output from the speaker will be minimized. 
This helps reduce the probability of feedback from the speaker. 
A shield may also be secured about the microphone 18 to reduce the 
probability of feedback. In addition, the digital signal processing stage 
14 may reduce undesirable resonance effects by detecting zero crossings of 
high amplitude components to initially detect a resonance problem and then 
suppress those resonant frequencies. For example, the FFT stage 24 may 
selectively use the inverse transfer function matrix to suppress the 
resonant components of the signal that represents the undesirable 
resonance. 
Although not specifically shown in FIG. 2, the microphone 18 may be placed 
in a mouth guard, such as a plastic mouthpiece (also not shown), which may 
be worn by the snoring person 1. The microphone 18 may be a cordless 
microphone as known in the art so that the mouth piece and microphone 
combination is not uncomfortable or unnecessarily restrictive for the 
snoring person 1. 
The snoring attenuation system 10 produces a doublet between the signal 
emission plane of the speaker 32 and the mouth 34 of the snoring person. 
Hence, a non-snoring person, such as a spouse lying next to the snoring 
person 1, will hear a suppressed snoring sound since the snoring sound is 
canceled at an angle of approximately 90 degrees with respect to the 
direction or angle between the speaker 32 and the mouth of the snoring 
person. It is preferred that the speaker 32 is positioned in an opposing 
direction to that of the snore source signal generator. Typically, the 
microphone 18 should be no more than approximately 2 centimeters away from 
the mouth of the snoring person 20 and the speaker 32 should be no more 
than approximately 40 centimeters from the mouth of the snoring individual 
1. A preferred speaker distance is approximately 5-10 cm. 
FIG. 4a pictorially represents another embodiment of the invention that 
includes a plurality of speakers 32, 40, and 42 which may be selectively 
activated to output a snore canceling signal depending upon the head 
orientation or mouth location of the snoring person 1. As shown, the 
speaker 32 may be mounted to a headboard 44 or other suitable mount, so 
that one speaker may be positioned above the head to effectively minimize 
the distance between the cancel speaker and the snore signal source and to 
provide a 90.degree. cancellation plane angle with the ears of the 
adjacent non-snoring person. Speakers 40 and 42 may be located on either 
side of the snorer's head in a pillow. However, the speaker 40 and 42 may 
also be suitably mounted to the headboard or otherwise resting on the bed 
at a distance which allows the snoring individual to uninhibitedly rotate 
the head. 
FIG. 4b is a schematic representation of a snoring attenuation system 46 as 
shown in FIG. 4a. The system 46 determines a location of the snoring 
source. The system 46 tracks the location or position of the snoring 
source signal using sensors. The system actuates one of the speakers to 
optimize cancellation of the snoring sound signal through ultrasonic 
sensors or other inaudible sensing mechanism. An ultrasonic transmitter 48 
may be placed in the mouth piece worn by the person 20 or on the 
microphone 18 and transmits a pulsating or continuous ultrasonic signal. 
An ultrasonic sensor will not be heard by the snoring person nor the 
non-snoring persons. Ultrasonic receivers 50a, 50b and 50c, are located in 
a corresponding speaker 42, 32 and 40, respectively. The ultrasonic 
receivers 50a-50c are connected to an A/D converter 54 through amplifiers 
56a, 56b and 56c. The ultrasonic receivers 50a-50c are suitably located in 
the speakers to detect the ultrasonic signal from the ultrasonic source 
48. 
A speaker selector 58 receives the detected ultrasonic signal and 
determines which ultrasonic receiver 50a-50c is receiving the strongest 
signal and may also determine the elapsed time for an emitted signal to be 
received by a detector to determine the distance between a selected 
speaker and the snore source. The speaker selector 58 is connected to a 
multiplexer 60 which activates the proper speaker 42, 32 or 40, via 
control from the speaker selector 58. The speaker selector 58 may also 
include the D/A function and amplification function of D/A 28 and 
amplifier 30 shown in FIG. 2. Furthermore, the speaker selector 58 may 
include the control functions of speaker controller 27, also as described 
with reference to FIG. 2. 
For example, if ultrasonic receiver 50a which is located in speaker 42 
receives the strongest ultrasonic signal from ultrasonic generator 48, the 
speaker controller 58, may then turn off speakers 32 and 40 so that the 
canceling signal is output by speaker 42. The speaker controller may also 
evaluate the elapsed time between a signal transmission from a transmitter 
and the detection by a corresponding receiver to evaluate the distance 
between the snore source and the speaker and turn on a speaker that is 
closer to the snore source although that speaker may not be receiving the 
strongest ultrasonic signal. 
The ultrasonic sensors 50a-50c in effect determine which speaker is closest 
and/or has the best directional position to the source snore sound signal. 
As shown, the canceling signal generating stage 14 is coupled to the 
speaker controller 58 so that a suitable canceling signal may be 
multiplexed to the proper speaker. 
Selective control of multiple canceling signal output devices as shown in 
FIGS. 4a and 4b, allow a snoring individual to continue snoring while the 
system determines the direction from which the strongest snoring signal is 
generated and/or the closest speaker to the snore source and selects the 
appropriate speaker from which the canceling signal is output. This offers 
substantially unrestrictive movement for the snoring individual and does 
not require an adjacent non-snoring individual to wear a restrictive 
snoring suppression system. It will be recognized that other suitable 
inaudible sensing systems may be used such as infrared sensors or the like 
which will not disturb either the snoring individual or non-snoring 
person. 
The speaker controller 58 may be a suitable microcomputer containing 
software to determine which speaker is receiving the strongest signal. The 
speaker controller 58 may also be adapted to turn the speakers 42, 32 and 
40 off or otherwise prevent a canceling output signal from being 
communicated to the speakers 42, 32 and 40. For example, a canceling 
signal may not be output when the sensors 50a-50c receive a signal having 
a level below a predetermined threshold or the elapsed detection time by 
an ultrasonic pair is too long (as described with reference to the 
controller 27 in FIG. 2). This may indicate that the snoring individual is 
too far from the speakers 50a-50c so that the canceling signal should not 
be output. Such a shut down mode avoids the cumulative affect of reducing 
snoring sounds being output from the speakers when such signals would not 
efficiently cancel a snoring signal. For example, if the speaker is too 
far away from the snoring signal source, and not in a substantially 180 
degree phase difference and same amplitude at a point close enough to the 
source, canceling will not occur and the canceling signal will effectively 
add to the snoring signal and compound the snoring problem. 
The speakers 32, 42 and 40 may each have a different frequency response 
range to facilitate varying canceling snoring signal outputs. For example, 
one speaker may have a frequency range of 20 Hz to 300 Hz, another speaker 
may have a frequency range of between 300 Hz and 500 Hz and a third 
speaker may have a frequency range of between 500 Hz and 1000 Hz. Such a 
system may be advantageous where the frequency response delay for one 
speaker over a certain range of frequencies is different from that of 
another one of the speakers. For example, where a speaker has a 
substantially constant delay over a frequency range of 20 Hz to 300 Hz, it 
may be advantageous to utilize that speaker for similarly ranged snore 
signal cancellation. Whereas it may be advantageous to use another speaker 
having a same delay over a different frequency response thereby reducing 
the processing time required by the digital filter 24. 
Since low frequency speakers tend to be larger in size and given the nature 
of the omnidirectional sound at the low frequencies, the large speakers 
may be placed further away from the source. In contrast, it may be 
preferable to position high frequency speakers (smaller speakers) closer 
to the snore signal source. 
In another embodiment, a single movable speaker may be employed with a 
sensing mechanism as previously described so that a speaker such as 32 may 
move in corresponding position with the mouth of a snoring individual. A 
drive motor 59 may receive a drive signal from the position sensing 
mechanism such as the speaker selector 58 to move the speaker to a 
suitable location. It will be recognized that the movable speaker 32 may 
be mounted on a slide rail 61 or other suitable mount and may be secured 
to a bed frame or other housing which facilitates movement of the speaker 
far enough above the individuals head so that the snoring individual is 
not unduly restricted. 
It has been found that a difficult part in global cancellation of a point 
source in an open area is that physical systems have built-in delays 
throughout. For example, the speaker may have a delay associated with it 
which may vary over the frequency range of the speaker. Such a delay may 
result in a 0.2 to a 1 millisecond delay. Also, at low frequencies, the 
speaker may output a canceling signal that may be ahead in phase which 
must be taken into account by the output signal generating stage 14. 
Another example may be the microphone 18 and amplifier 20, each of which 
also have a delay associated with them. The doublet mechanism requires 
that a canceling signal (the output from the speaker) will be close to the 
snoring source (5 to 40 cm). In addition, any delay will cause the 
canceling signals not to cancel and in some cases may even strengthen the 
snoring signal by adding with the snoring signal if sufficient signal 
phase discrepancies are encountered (such as may occur at high 
frequencies). 
Consequently, to avoid such drawbacks, the aforedescribed system "predicts" 
the cancellation signal so that the cancellation signal is output (as 
measured at the plane of the speaker) at a moment in time which is 
synchronized and without delay with respect to the snore source signal 
emitted from the snore source. Therefore the system as described above 
finds particular application where the snore signal is a stochastic 
signal. Based on the foregoing description, it will be evident that the 
system 10 globally suppresses the snore source signal proximate the source 
by creating a doublet between the cancel signal as measured at the plane 
of the speaker and snore signal source (at the mouth or received by the 
microphone in the mouth). 
FIG. 5 discloses another embodiment of the invention wherein filter 90 is 
used to filter out the snore signal to the ear of an adjacent non-snoring 
individual 82. The system 80 allows a non-snoring person 82 or other 
individual other than the snoring person to select between various sound 
inputs such as ambient noise or input from another sound source. 
Input from another sound source may be received from a microphone 87 which 
may be in another room of the house so that an alarm or other warning 
system may be heard. Another input may be a stereo input or other type of 
audio input. A switch 88 couples with the microphone 87 and the filter 90 
which may be an adaptive filter, a fixed filter or any other suitable 
filter and is connected so that the microphone 87 may be switched directly 
to the earphone 86 so that the adjacent individual 82 may listen to some 
other audio input. When the switch 88 is switched to the snore filtering 
mode, the filter 90 serves to filter out the snoring noise. 
Referring to FIGS. 5 and 6, the earphones 86 also include a cover 101 for 
encapsulating an ear 112 and provides an acoustical seal about the ear. 
The cover 101 includes a channel 102 through which a sound tube 104 may be 
inserted. The sound tube 104 may have a plug 106 positioned on a distal 
end thereof. The plug 106 includes a channel 108 for receiving the sound 
tube 104. The switch 88 may be used to switch in outside audible sounds 
from other rooms or may be used to switch in sounds from the room which 
may include snoring sounds. The filter 90 may filter out the snoring and 
pass all other sound so that the wearer of the cover 101 will only hear 
non-snore sounds. 
FIG. 7 depicts the system of FIG. 2 with the addition of a microphone 110 
located in a headset 112 on an adjacent person 5 and positioned to receive 
a suppressed snore signal. The microphone 110 receives the suppressed 
snore signal as it is heard by the person 5. The received suppressed 
signal serves as feedback or an error signal to the system 10 so that the 
system may evaluate the effectiveness of the suppression and also adjust 
the snore canceling signal 8 to optimize effectiveness. 
The microphone may be connected to an amplifier 114 similar to amplifiers 
20 and 30. An A/D converting circuit 116 converts the analog received 
suppression signal to a digital signal. The digital suppressed signal 
serves as input to the adaptive filter 25. The adaptive filter 25 may use 
the suppressed signal to correct the coefficients 29 to better suppress 
the snore signal 3. The microphone may also be positioned anywhere in the 
room or at the plane of emission of the speaker. 
In yet another embodiment, the distance between the transducing device and 
the snore source may be minimized by the use of a sound waveguide. For 
example, a sound waveguide may be attached to the speaker so that the 
plane of emission of the speaker is closer to the mouth of the snoring 
person. 
Specific embodiments of a novel system for snoring suppression has been 
described for the purposes of illustrating the manner in which the 
invention may be used and made. It should be understood that the 
implementation of other variations and modifications of the invention in 
its various aspects will be apparent to those skilled in the art, and that 
the invention is not limited by the specific embodiments described. It is 
therefore contemplated to cover by the present invention any and all 
modifications, variations, or equivalents that fall within the true spirit 
and scope of the basic underlying principles disclosed and claimed herein.