Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
2001-11-09
2003-05-27
Pope, Daryl (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S544000, C340S550000, C340S566000, C073S587000, C073S594000, C381S015000, C381S016000
Reexamination Certificate
active
06570500
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method, a module, a device, a module and a system for detecting an environment noise by evaluating an infrasonic signal. Particularly, the method according to the present invention provides a continuous level adjustment algorithm to adapt the detection level to a noise background for evaluating the infrasonic signal, for example to monitor a certain ambiance or environment.
2. Description of the Prior Art
Sound frequencies in a frequency range of about 0.1 Hz up to 20 Hz are normally designated as infra-sound. Infra-sound or an infrasonic pulse is generated by small changes of the air pressure, respectively. Such small changes of the air pressure may be generated by opening or closing of a door or a window but even by persons moving though a room. Due to the object surfaces moving through the air small changes of the air pressure are released such that infrasonic pulses are emitted by the respective moving object. These infrasonic pluses or infra-sound may by detected in a radius of up to 50 m away from the emerging object. But the radius of detection is further dependent on background noise and the space within which the infra-sound is propagating.
To detect infra-sound special microphones are used. These microphones are adapted to detect low frequency sound since low frequency sound is additionally often of low amplitude or low power, respectively. Nevertheless, microphones able to detect infra-sound (about 0.1 Hz to 20 Hz) and speech (about 200 Hz to 15 kHz) are available at reliable detection sensitivity.
A couple of detector systems and devices are in use to protect environments, rooms, homes, buildings and cars from being accessed in an unauthorized way. The mainly used detectors are ultrasonic motion detectors, infra-red detectors, light barriers and the like. These detectors may be combined with an alarm system in order to secure a respective object. Also infra-sound detectors are able to monitor a space signalling an opening of a door or a window or even a motion within the monitored space. Such infra-sound detectors are well known and used in motor vehicles to trigger an alarm system for example to prevent burglary of the motor vehicles.
Applications are known where separate infra-sound detecting devices are connected to a mobile phone, like described in WO 99/53456. These infra-sound detecting devices are used to trigger or rise any kind of alarm or monitoring action.
Normally, special infra-sound detecting microphones are used for detecting infra-sound events. These infra-sound microphones are expensive and require the implementation of a separate infrasound microphone. The usage of microphones detecting sound in a wide frequency range covering infra-sound frequencies and voice/speech frequencies enables extending the devices processing voice/speech audio signals to an alarm system by operating these devices to evaluate infrasonic signals detected by the microphones.
Usually, infra-sound detection systems, especially used in combination with alarm systems, employ fixed detection levels. The detection level defines an infra-sound level, normally an infra-sound amplitude level, at which a detected infra-sound event is interpreted as event to be signalized for example by an alarm of the alarm system. The fixed detection level is often adjustable to the environmental noise background but the environmental noise background can change due to outer effects. For example, while monitoring the infra-sound within a motor vehicle, the monitored infra-sound background level is dependent upon the place where the motor vehicle is parked. Near a heavily used road the infra-sound background level may be higher than within a residential area. That means, that in case of a low detection level a lot of false alarms are triggered or in case of a high detection level a careful opening of a door might be unnoticed. Both cases are undesired.
SUMMARY OF THE INVENTION
The invention is a method for monitoring an environment by evaluating an infrasonic signal taking a sound of said environment.
The invention is a module of a surveillance system for monitoring the environment by evaluating an infrasonic signal.
The invention is a device of a surveillance system for monitoring by evaluating an infrasonic signal
The invention is a system of a surveillance system for monitoring by evaluating an infrasonic signal.
Therefore, a continuous level adjustment algorithm provides the possibility to pre-determine a detection level which is continuously adapted to the background level. The number of false alarm of an alarm system which uses this algorithm to evaluate measured infra-sound can be reduced while the overall sensitivity of the infra-sound event detection is quite low arid hence reliable.
According to a first aspect of the invention a method of a surveillance system for monitoring by evaluating an infrasonic signal is provided. An infrasonic signal is averaged to yield an averaged infrasonic signal. The averaged infrasonic signal is mapped according to a function to yield an infrasonic noise signal. This infrasonic noise signal is averaged to yield an averaged infrasonic noise signal. By offsetting the averaged infrasonic noise signal with an offset value an infrasonic level signal is provided. This infrasonic level signal is compared with the averaged infrasonic signal. According to the comparison if the averaged infrasonic signal is greater than the infrasonic level signal a trigger signal is generated.
The infrasonic signal may be provided by filtering. The filtering may be employed on signals comprising infrasonic signals and non-infrasonic signals, i.e. signals of non-infrasonic frequency. Hence, the characteristic of the filtering may be limited to an infrasonic frequency range. The filtering may be a band-pass filter employed to extract an infrasonic signal. The band-pass filter characteristic may be limited to an infrasonic frequency range. A low-pass filter may also be employed for extracting the infrasonic signal. Accordingly, the low-pass filter characteristic may be limited to an infrasonic frequency range.
The averaged infrasonic signal may be a root mean square infrasonic signal. But also further averaging methods may be employed on the infrasonic signal to yield the averaged infrasonic signal.
The mapping of the averaged infrasonic signal may also comprise an additional rating of the function result with the averaged infrasonic noise signal. The function for mapping may be a non-linear function. This function may be used for weighting an additional rating signal, especially the averaged infrasonic noise signal. The function argument may by the result of an arbitrary combination of the averaged infrasonic signal arid the averaged infrasonic noise signal. Particularly, the argument may be the result of the division of the averaged infrasonic signal and the averaged infrasonic noise signal. Moreover, the function may map the result the division of the averaged infrasonic signal and the averaged infrasonic noise signal to provide a function result and this function result may be multiplied with the averaged infrasonic noise signal to provide the infrasonic noise signal.
The offset value may be an absolute offset value, increasing the averaged infrasonic noise signal by a constant absolute value. The offset value may be a relative offset value. The increasing offset of the averaged infrasonic noise signal is determined relatively to the averaged infrasonic noise signal. Further, the offset value may be multiplied with the averaged infrasonic noise signal to provide the infrasonic level signal. Particularly, the offset value may be defined by a signal-to-noise ratio (SNR). Moreover, the offset value may be adjustable to adapt the evaluation method to different operating conditions.
According to another aspect of the invention a software tool of a surveillance system for monitoring by evaluating an infrasonic signal is provided. The software tool comprises program potions for carrying out the operat
Antonelli Terry Stout & Kraus LLP
Nokia Corporation
Pope Daryl
LandOfFree
Infra-sound surveillance system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Infra-sound surveillance system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Infra-sound surveillance system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3002726