Patent Application
20130279710
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 pressure 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 from a location outside of or downstream from the horn. The sound pressure sensor is typically a microphone or some other pressure sensing device. Unfortunately, such sound pressure sensors can be relatively expensive, and they can be somewhat fragile. Also, the accuracy and efficiency of such a sound pressure sensor can degrade over time.
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.
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 result 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.
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 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.
In 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 alternate 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 alternate 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.
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 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.
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.
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.
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
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 frequency 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 frequency 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 controller 22 of the diagnosing unit 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
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.
