BACKGROUND OF THE INVENTION
Acoustic horns typically include a driver or sound generating device that is
coupled to a horn which provides an acoustic impedence match between the sound
generating device and free air. This has the effect of maximizing the efficiency with
which sounds waves generated by the sound generating device are transferred into
free air.
Sounds waves in their simplest form are pressiu-e waves that travel through a
medium. Various uses for acoustic horns exist today. Those uses include emitting
sound waves as a signaling device to alert people to danger or damage. An acoustic
horn can also emit sound waves to clean a surface of debris. In many circumstances,
especially if acoustic horns are located in remote areas or are used for critical
purposes, it is important for operators to know when the output of an acoustic horn is
starting to degrade, or that the acoustic horn is not operating at all. Regular scheduled
maintenance of the driver and horn can help to abate operational concerns, but the
need exists for accurate, immediate feedback of horn operation.
Various different systems for sensing how well an acoustic horn is operating
have been proposed. In most existing systems, a sound pressure sensor senses
pressure waves generated by the acoustic horn within the horn structure itself, or fi^om
a location outside of or downstream fi^om the horn. The sound pressure sensor is
typically a microphone or some other pressure sensing device. Unfortunately, such
soimd pressure sensors can be relatively expensive, and they can be somewhat fi'agile.
Also, the accuracy and efficiency of such a sound pressure sensor can degrade over
time.
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These sound pressure sensors may also be exposed to harsh and caustic
conditions. By their nature, the sound pressure sensors must have a clear, open path
to the horn. The medium between the horn and the sound pressure sensor can change
drastically in temperature, density, and contamination within a given time period,
which can greatly affect the signal output by the sensor. And because the signals can
vary considerably, detecting degraded performance can be difficult or impossible. As
a result, in many instances it is only possible to determine whether an acoustic horn is
operating. It can be impossible to determine the current level of performance.
BRIEF DESCRIPTION OF THE INVENTION
In one aspect, the invention may be embodied in a method of monitoring the
performance of an acoustic horn which includes a step of sensing vibrations of an
acoustic horn while the acoustic horn is activated with a sensor that outputs a
vibration signal indicative of the sensed vibrations. The method also includes steps of
comparing the vibration signal to at least one threshold value or pattern, and
generating a report signal based on a result of the comparing step.
In another aspect, the invention may be embodied in a system for monitoring
the performance of an acoustic horn that includes means for sensing vibrations of an
acoustic horn while the acoustic horn is activated, wherein the sensing means outputs
a vibration signal indicative of the sensed vibrations. The system also includes means
for comparing the vibration signal to at least one threshold value or pattern, and
means for generating a report signal based on a resuh of the comparing step.
In another aspect, the invention may be embodied in a system that includes a
vibration sensor that senses vibrations of an acoustic horn while the acoustic horn is
activated, wherein the vibration sensor outputs a vibration signal indicative of the
sensed vibrations. The system also includes a comparison unit that compares the
vibration signal to at least one threshold value or pattern, and a report unit that
generates a report signal based on information generated by the comparison unit.
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BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a diagram of a system for sensing an operational condition of an
acoustic horn;
Figure 2 is a block diagram illustrating elements of a controller of the system
illustrated in Figure 1;
Figure 3 is a diagram illustrating a vibration signal that is output by a sensor of
the system illustrated in Figure 1; and
Figure 4 is a flow chart illustrating steps of a method of sensing the
operational status of an acoustic horn.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Figure 1 shows a typical acoustic horn 10, which includes a driver 12 and a
horn 14. The driver 12 creates sound pressure waves, and the horn 14 provides an
acoustic impedence match between the driver 12 and free air. The driver 12 typically
includes a diaphragm that vibrates to create sound pressure waves. Various different
mechanisms can be used to cause the diaphragm to vibrate in a controlled fashion to
generate the desired sound pressure waves. However, because the diaphragm is
mounted in a housing of the driver 12, whenever the diaphragm is vibrating to
produce sound pressure waves, the housing of the driver 12 also vibrates, albeit less
than the diaphragm itself
A system for monitoring the performance or operational status of the acoustic
horn, and for diagnosing problems, makes use of one or more vibration sensors 20,
21, which are operationally mounted on the acoustic horn. In some embodiments, a
vibration sensor 20 is mounted on the housing of the driver 12. In other
embodiments, a vibration sensor 21 may be mounted on the horn 14. Some
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embodiments may only include a single vibration sensor, while other embodiments
may include multiple vibration sensors.
When a vibration sensor 20 is mounted on the housing of the driver 12, the
vibration sensor 20 outputs a vibration signal indicative of the vibration of the driver
12. The vibration signal may include both an amplitude and a frequency.
[n some embodiments, the vibration sensors 20, 21 may be accelerometers.
Low cost, durable accelerometers which could be used as the sensors 20, 21 are
widely commercially available. In altemate embodiments, other types of sensing
devices that are capable of sensing vibration could be used instead of an
accelerometer. Regardless of the type of sensor that is used, the sensors 20, 21 output
a vibration signal indicative of the vibrations which are generated when the acoustic
horn 10 is operating.
The vibration sensors 20, 21 can be attached to the acoustic horn 10 via any
suitable fastening means. For example, the vibration sensor could be attached to a
portion of the acoustic horn 10 via an adhesive, or via a mechanical fastener such a
screw or bolt. Further, a bracket or other mounting device may be provided on the
acoustic horn 10 to receive and hold the vibration sensors 20, 21.
Each vibration sensor is operationally coupled to a controller 22 that receives
the vibration signal generated by each vibration sensor 20, 21. In some embodiments,
a wire or cable may run from each vibration sensor 20, 21 to the controller 22. In
ahemate embodiments, the vibration sensors may output wireless signals that are
received by the controller 22. In this type of an embodiment, each vibration sensor
20, 21 may be coupled to a wireless transmitter, and the controller 22 may be coupled
to a wireless receiver. The signals output by each vibration sensors would be
provided to a wireless transmitter, and the wireless transmitter would send the signal
to the wireless receiver. The wireless receiver would then provide the signal to the
controller 22.
S'
Figure 2 illustrates some elements of the controller 22. As shown in Figure 2,
the controller includes a receiving unit 24 that receives a vibration signal from at least
one vibration sensor. The controller also includes a comparison unit 26 that compares
one or more characteristics of the vibration signal to one or more predetermined
threshold values or patterns. In some embodiments, simply determining how one or
more characteristics of the vibration signal compare to a threshold value may provide
all the required information.
In some embodiments, the controller may also include a diagnosing unit 27.
The diagnosing unit 27 may compare one or more aspects of the vibration signal to
threshold values or to patterns to determine whether the acoustic horn is operating
properly. If the diagnosing unit 27 determines that the acoustic horn is not operating
properly, the diagnosing unit 27 may be able to determine what is causing the
problem by examining the vibration signals from one or more vibration sensors that
are attached to the acoustic horn.
The comparison unit 26 and/or the diagnosing unit 27 may compare a
vibration signal from one or more vibration sensors to a baseline established for that
particular acoustic horn when the acoustic horn is first installed or when the vibration
sensors are first installed on the acoustic horn. This would allow real world testing to
determine what characteristics of the vibration signal should be considered "normal."
If testing is conducted upon installation, to establish a baseline level for the signal
from the vibration sensor, the real world conditions that exist for that particular
acoustic horn can be taken into account.
In other embodiments, the comparison unit 26 and/or the diagnosing unit 27
may compare a vibration signal from one or more vibration sensors to baseline values
that have been established from testing multiple different acoustic horns in similar
installation environments.
The diagnosing unit 27 may employ predictive analytics, based upon how
similar acoustic horns have performed in the past, to determine the operational status
c
of the acoustic horn. If past history shows that a particular pattern of the vibration
signal indicates that the acoustic horn is about to fail, the diagnosing unit 27 can alert
maintenance personnel of the need to take corrective action before the acoustic horn
actually fails.
The controller 22 also includes a reporting unit 28 that generates a report
signal indicative of the level of performance or the operational state of the acoustic
horn. The report signal may also indicate the cause of any problems that have been
detected. The report signal is based on information generated by the comparison unit
26 and/or the diagnosing unit 27.
In some embodiments, the controller may further include a recording unit 29.
The recording unit 29 could record all or selected portions of the vibration signals
generated by one or more vibration sensors. The recording unit 29 may also record
the signal that is applied to the driver 12 of the acoustic horn, so that the signal output
by one or more of the vibration sensors can be compared to the signal applied to the
driver, which may facilitate the diagnosis of a problem or the determination of the
operational status of the acoustic horn.
Figure 3 illustrates a vibration signal 30 that might be generated by a vibration
sensor. Figure 3 shows the amplitude of the vibration signal over time. As is
apparent from Figure 3, when the acoustic horn 10 is not operating, the vibration
signal 30 has a very small amplitude, basically representing a background noise level.
However, when the acoustic horn is activated, and the acoustic horn vibrates, the
amplitude of the vibration signal 30 becomes relatively large. The vibration signal 30
in Figure 3 includes five high ampUtude segments 100, 102, 104, 106 and 108 which
indicate five corresponding points in time when the acoustic horn was in operation.
Figure 3 also shows two different threshold values 40 and 60, which are
represente4 by dashed lines. The amplitude of the vibration signal 30 is compared to
the two threshold values 40, 60 to determine the level of performance or the
operational status of the acoustic horn. For example, if the amplitude of the vibration
^
signal 30 is greater than the first threshold value 40, the acoustic horn is deemed to be
operating properly. Figure 3 illustrates that the vibration signal 30 is above the first
threshold value 40 during the first two times 100 and 102 that the acoustic horn was
operating.
If the amplitude of the vibration signal 30 falls below the first threshold value
40, but is still greater than the second threshold value 60, the acoustic horn is deemed
to be operating in an impaired or degraded fashion. Figure 3 illustrates that the
amplitude of the vibration signal 30 fell into this range during the third and fourth
times 104, 106 that the acoustic horn was operating.
If the amplitude of the vibration signal 30 falls below the second threshold
value 60, the performance of the acoustic horn is deemed to have fallen to an
unacceptably low level. Figure 3 illustrates that the amplitude of the vibration signal
30 fell below the second threshold value 60 during the fifth time 108 that the acoustic
horn was operating. This would indicate that the acoustic horn should be repaired or
replaced.
In some embodiments, the comparison unit 26 of the controller 22 compares
the amplitude of a vibration signal generated by a vibration sensor to predetermined
threshold values, as illustrated in Figure 3, to determine the level of performance or
the operational status of the acoustic horn. The information generated by the
comparison unit 26 is then used by the reporting unit 28 to generate a report signal
indicative of the determined level of performance or operational status.
Although the example given above included the use of two different
predetermined threshold values, in alternate embodiments, only a single threshold
value might be used. So long as the amplitude of the vibration signal remains above
the threshold value when the acoustic horn is operating, the performance would be
deemed acceptable. If the amplitude falls below the threshold value, the performance
would be deemed unacceptable.
?
As noted above, the threshold values(s) to which a vibration signal is
compared could be established by conducting real world testing. The threshold
values(s) could also be automatically set by the controller based on analytic tolls.
Likewise, the amplitude of the vibration signal could be compared to more than two
threshold values to make finer determinations about how well the acoustic horn is
operating. Predictive analytics can be used to chart the predicted remaining life of an
acoustic horn to aid in forecasting the need for replacement parts and the time when
they should be replaced to avoid complete failure of the acoustic horn.
Also, in some embodiments, the acoustic horn might be configured to output
different types of sounds or different volume levels. If this is the case, the threshold
value(s) to which the vibration signal is compared would be adjusted accordingly.
Also, the above examples involved comparing the amplitude of the vibration
signal to one or more threshold values. In alternate embodiments, the frequency of
the vibration signal might instead be compared to one or more threshold frequency
values.
For example, in some embodiments, if the frequency of the vibration signal is
greater than or lower than a threshold frequency value, the performance of the
acoustic horn would be determined to be acceptable. Otherwise, the performance
would be deemed unacceptable. Likewise, the performance might be deemed
acceptable only if the fi-equency of the vibration signal falls between two threshold
frequency values. If the frequency of the vibration signal is greater than the larger
threshold frequency value or lower than the lower threshold fi"equency value, the
performance would be deemed unacceptable.
In still other embodiments, both the amplitude and the frequency of the
vibration signal may be compared to threshold values to determine the level of
performance of the acoustic horn. Also, in still other embodiments, other
characteristics of the vibration signal may be compared to one or more threshold
values to determine the level of performance of the acoustic horn.
?
In some embodiments, characteristics of the vibration signal may be compared
to characteristics of a drive signal applied to the driver 12 of the acoustic horn 10 to
determine the level of performance or the operational status of the acoustic horn. For
example, if aspects of the vibration signal, such as its waveform, closely match
corresponding aspects the drive signal, the acoustic horn would be deemed to be
providing acceptable performance. If the sensed aspects of the vibration signal do not
closely match corresponding aspects of the drive signal, the acoustic horn would be
deemed to be providing unacceptable or poor performance.
When two or more vibration sensors are provided on an acoustic horn, the
vibration signals generated by all of the vibration sensors may be used together to
determine the operational status of the acoustic horn, or to diagnose a problem. For
example, if a first vibration sensor attached to the driver housing provides a good
vibration signal when the acoustic horn is activated, but a second vibration sensor on
the horn portion provides little or no signal when the horn is activated, this
information could indicate that the driver is operating properly, by that the horn
portion is blocked or otherwise impaired.
A diagnosing unit 27 of a controller could compare the signals generated by
one or more vibration sensors to predetermined patterns to determine the operational
status of an acoustic horn, and/or to diagnose particular problems or faults. The
predetermined patterns could be stored in a database that is accessible to the conttoller
22 of the diagnosing xmit 27.
In some embodiments, the reporting unit 28 may be capable of generating a
display signal that drives a display screen. In this sort of an embodiment, the display
screen could illustrate the pattern of a vibration sensor signal, as shown in Figure 3.
The display may also illustrate the pattern of a drive signal applied to the driver of the
acoustic horn, to thereby facilitate a comparison of the drive signal to the vibration
sensor signal.
h
Figure 4 illustrates steps of a method of determining the operational status or
performance of an acoustic horn. The method begins in step S400 where one or more
vibration sensors sense vibration of a driver of an acoustic horn and output one or
more vibration signals. In step S402, a controller obtains the vibration signal(s). In
step S404, one or more aspects of the vibration signal(s) are compared to one or more
threshold values or to one or more patterns. Then, based on the result of step S404, a
report signal indicative of the operational status, or level of performance of the
acoustic horn, or a diagnosis of a fault, is output in step S406.
While the invention has been described in connection with what is presently
considered to be the most practical and preferred embodiments, it is to be understood
that the invention is not to be limited to the disclosed embodiments, but on the
contrary, is intended to cover various modifications and equivalent arrangements
which are encompassed within the spirit and scope of the appended claims.
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SYSTEMS AND METHODS FOR SENSING THE OPERATIONAL STATUS OF AN
ACOUSTIC HORN
PARTS LIST
Acoustic horn 10
Driver 12
Horn 14
Vibration sensors 20, 21
Controller 22
Receiving unit 24
Comparison unit 26
Diagnosing unit 27
Reporting unit 28
Recording unit 29
Vibration signal 30
Threshold values 40 and 60
High Amplitude segments 100, 102, 104, 106 and 108
I J -

We Claim:
1. A method of monitoring the performance of an acoustic hom,
comprising:
sensing vibrations of an acoustic hom while the acoustic hom is
activated with a sensor that outputs a vibration signal indicative of the sensed
vibrations;
comparing the vibration signal to at least one threshold value or
pattern; and
generating a report signal based on a result of the comparing step.
•
2. The method of claim 1, wherein the sensing step comprises sensing
vibrations of the acoustic hom driver housing with an accelerometer.
3. The method of claim 1, wherein the sensing step comprises sensing
vibrations of the acoustic hom driver with an accelerometer that is mounted on the
acoustic hom driver.
4. The method of claim 1, wherein the comparing step comprises
determining whether an amplitude of the vibration signal is greater than a first
threshold value.
^ 5. The method of claim 4, wherein if the amplitude of the vibration signal
is greater than the first threshold value, the generating step comprises generating a
report signal that indicates that the acoustic hom is operating normally, and wherein if
the amplitude of the vibration signal is smaller than the first threshold value, the
generating step comprises generating a report signal that indicates that the acoustic
hom is not operating normally.
6. The method of claim 4, wherein if the amplitude of the vibration signal
is smaller than the first threshold value, the comparing step further comprises
1>
determining whether the amplitude of the vibration signal is greater than a second
threshold value.
7. The method of claim 6, Vk'herein if the amplitude of the vibration signal
is less than the first threshold value and greater than the second threshold value, the
generating step comprises generating a report signal that indicates that the horn is
operating with less than optimal performance, and wherein if the amplitude of the
vibration signal is less than the second threshold value, the generating step comprises
generating a report signal that indicates that the horn is malfunctionmg.
8. The method of claim 1, wherein the comparing step comprises
determining whether a fi-equency of the vibration signal is greater than a first
threshold frequency.
9. The method of claim 1, wherein the sensing step comprises sensing the
vibration of an acoustic horn with a plurality of vibration sensors that output a
corresponding plurality of vibration signals.
10. The method of claim 9, wherein the comparing step comprises
comparing the vibration signals output by the plurality of vibration sensors to at least
one predetermined pattern.
^ P 11. A system for monitoring the performance of an acoustic horn,
comprising:
means for sensing vibrations of an acoustic horn while the acoustic
horn is activated, wherein the sensing means outputs a vibration signal indicative of
the sensed vibrations;
means for comparing the vibration signal to at least one threshold value
or pattern; and
means for generating a report signal based on a result of the comparing
step.
IV
12. A system for monitoring the performance of an acoustic horn,
comprising:
a vibration sensor that senses vibrations of an acoustic horn while the
acoustic horn is activated and that outputs a vibration signal indicative of the sensed
vibrations;
a comparison unit that compares the vibration signal to at least one
threshold value or pattern; and
a report unit that generates a report signal based on information
generated by the comparison unit.
^ ^ 13. The system of claim 12, wherein the vibration sensor comprises an
accelerometer.
14. The system of claim 12, wherein the vibration sensor comprises an
accelerometer that is configured to be operatively mounted on an acoustic horn driver
of an acoustic horn.
15. The system of claim 12, wherein the vibration sensor comprises a
plurality of vibration sensors that output a corresponding plurality of vibration signals.
16. The system of claim 12, wherein the comparison unit is configured to
compare an amplitude of the vibration signal to at least one threshold value or pattern.
17. The system of claim 16, wherein the comparison unit is configured to
determine if the amplitude of the vibration signal is greater than first and second
threshold values.
18. The system of claim 17, wherein the report unit is configured to output
a report signal indicating that the acoustic horn is operating normally if the amplitude
of the vibration signal is greater than the first threshold value, wherein the report unit
is configured to output a report signal indicating that the acoustic horn is operating in
an impaired fashion if the ampUtude of the vibration signal is smaller than the first
threshold value but greater than the second threshold value, and wherein the report
unit is configured to output a report signal indicating that the acoustic horn is
malfunctioning if the amplitude of the vibration signal is smaller than the second
threshold value
19. The system of claim 12, wherein the comparison unit is configured to
compare a frequency of the vibration signal to at least one threshold value or pattern.
20. The system of claim 12, wherein the comparison unit is configured to
^ ^ diagnose specific faults based on the vibration signal.