Shaped modulation audible alarm

A method and apparatus for providing an audible alarm signal. The method and apparatus includes creating a rectangular pulse signal having a desired period and a desired first amplitude, adding a shaped modulation component to the rectangular pulse signal from the desired first amplitude to a desired second amplitude to create a modulating waveform, creating a carrier signal, and combining the carrier signal and the modulating waveform to create the audible alarm signal.

TECHNICAL FIELD

This invention relates generally to a method and apparatus for creating an audible alarm and, more particularly, to a method and apparatus for creating a shaped modulation audible alarm.

BACKGROUND

Audible alarms of various types are used for a wide variety of purposes. For example, it is common practice to employ backup alarms on commercial vehicles and mobile work machines to notify those in the vicinity that the vehicle or machine is moving and may be moving toward them. Typical alarms of this type may use a repeating audible signal, such as a beeping sound.

In crowded or congested areas, repeated use of audible alarms may become a source of irritation to those not close enough in proximity to be intended recipients of the alarm signals. The harshness of the alarm sound, although necessary in many environments, becomes objectionable beyond the immediate work area.

One attempt to minimize this source of irritation has been to use self-adjusting alarms; that is, alarms which monitor ambient sound and vary the amplitude of the alarm signal in response. Although the levels of the alarms may be reduced in lower noise areas, thus reducing perceived harshness to persons in the area, the varying amplitudes of the alarm signals tend to confuse those in the immediate work area. For example, a person may be near a moving vehicle or machine yet believe that the vehicle or machine is further away due to a reduced amplitude alarm signal.

In addition to the above issues, many work areas require multiple alarms for a multitude of vehicles and machines. Persons within these crowded work areas may, over time, begin to disregard the sound of an audible alarm since it is difficult to differentiate between several alarms repeatedly going off throughout the work site.

SUMMARY OF THE INVENTION

In one aspect of the present invention a method for providing an audible alarm signal is disclosed. The method includes the steps of creating a rectangular pulse signal having a desired period and a desired first amplitude, adding a shaped modulation component to the rectangular pulse signal from the desired first amplitude to a desired second amplitude to create a modulating waveform, creating a carrier signal, and combining the carrier signal and the modulating waveform to create the audible alarm signal.

In another aspect of the present invention an apparatus for providing an audible alarm signal is disclosed. The apparatus includes a controller for creating an essentially rectangular pulse signal having a desired first amplitude, and for creating a carrier signal, a shape generator for adding a shaped modulation component to the pulse signal from the desired first amplitude to a desired second amplitude to create a modulating waveform, and a multiplier for combining the carrier signal and the modulating waveform to create the audible alarm signal.

In yet another aspect of the present invention an audible alarm signal is disclosed. The alarm signal includes an essentially rectangular pulse signal having a desired first amplitude, a shaped modulation component added to the pulse signal from the desired first amplitude to a desired second amplitude to create a modulating waveform, a carrier signal, and an audible alarm signal created from a combination of the carrier signal and the modulating waveform.

DETAILED DESCRIPTION

Referring to the drawings and the appended claims, a method and apparatus100is shown for providing an audible alarm signal416. The alarm signal may be suited for use in applications in which it is desired to provide notice of a situation. For example, an audible alarm signal may be used to provide notice to persons at a work site that a mobile machine or vehicle is moving. A common application involves the use of audible alarm signals as backup alarms for vehicles and mobile work machines. However, other applications may include security and intrusion systems for facilities, vehicles, and the like, and other applications in which it is desired to provide an alarm for a situation.

Referring toFIG. 1, a block diagram depicting an embodiment of the present invention is shown. It is noted that the embodiment ofFIG. 1is but one configuration that may be used in the present invention. Other variations may be employed without deviating from the spirit and scope of the invention.

A controller102may be used to perform a variety of functions. For example, the controller102may create an essentially rectangular pulse signal402, as shown inFIG. 4a. The pulse signal402may then be delivered to other components, such as a shape generator112and a gain control amplifier108, via a pulse signal line114. The controller102may perform additional functions, such as creating a carrier signal414, as depicted inFIG. 4c.

The pulse signal402, as shown inFIG. 4a, has a period404and a first amplitude406. For example, the pulse may have a period of about 1 Hertz and an amplitude of about 95 to 100 decibels. Other values for the period and amplitude may be used as well.

The carrier signal414typically is of a higher frequency than the pulse signal, for example about 1200 to 1250 Hertz.

The shape generator112may add a shaped modulation component408to the pulse signal402from the first amplitude406to a second amplitude410to create a modulating waveform412. AsFIG. 4bshows, the shaped modulation component408may be a sinusoidal component, for example gradually increasing to a maximum value and then gradually decreasing, thus simulating one half of a sinusoid. However, the shaped -modulation component may be configured as different shapes as well, for example, an inverse one half sinusoid, a full sinusoid, a step function signal, a sawtooth signal, and the like.

The second amplitude410may be greater in magnitude than the first amplitude406, for example 10 decibels greater. Alternatively, the second amplitude410may be lower in magnitude than the first amplitude406.

The gain control amplifier108receives the pulse signal402by way of pulse signal line114and may control the amplitude of the pulse signal402. For example, it may be desired to vary the amplitude of the pulse signal402to maintain the signal level a desired amount above an ambient sound level, such as 5 decibels above ambient. Advantages of varying the pulse signal402in this manner are described in detail below.

The gain control amplifier108outputs the amplitude-varied pulse signal402to a summing junction116to add the pulse signal402and the shaped modulation component408together, as shown inFIG. 4b. The resultant signal is the modulating waveform412.

In an alternate embodiment, shown inFIG. 2, a gain control amplifier and summing junction are not used. In this embodiment, the shape generator112receives the pulse signal402at fixed gain and adds the shaped modulation component408to create the modulating waveform412.

Referring back toFIG. 1, from the summing junction116the modulating waveform412is carried by way of modulating waveform line118to a multiplier122. The multiplier122also receives the carrier signal414from the controller102by way of a carrier signal line120. The carrier signal414and the modulating waveform412are combined by the multiplier122to create an audible alarm signal416.FIG. 4dillustrates an exemplary audible alarm signal waveform. The audible alarm signal416may then generate an audible alarm through a speaker126.

In certain applications, such as for backup alarm purposes, a backup sensor106may be used to determine a condition of a vehicle or mobile machine backing up, thus providing notice that a backup alarm needs actuation. The backup sensor106may be of a type well known in the art, such as a sensor configured to sense a transmission being in a reverse gear, movement in a reverse direction, and the like.

An ambient sound sensor104may be used to sense a level of ambient sound in the surrounding environment. The ambient sound sensor104may be a microphone or a speaker being used as a microphone which picks up sounds and transmits the sounds to the controller102for processing and determination of sound levels.

As noted above, it may be desired to maintain the amplitude of the pulse signal and thus the amplitude of the resultant audible alarm signal, a desired level above the ambient sound level of the surrounding environment. For example, the audible alarm signal may be 5 decibels above ambient sound levels. The result is that, as distance from the alarm signal source to a person hearing the alarm increases, the effect of the alarm signal changes due to the shaped modulation component408. At close ranges, the signal is perceived to be more like that of a carrier signal combined with a pulse signal402, since the pulse signal portion of the modulating waveform412is above the ambient sound floor. This has the effect of creating a somewhat harsh sounding alarm, thus placing more urgency in the effect of the alarm as the distance between alarm source and intended target decreases. However, at greater distances, the pulse signal portion of the modulating waveform drops into the ambient sound floor, and the intended listener only hears the shaped modulation component portion. The shaped modulation component408, by design, offers a less harsh sound to the perceiving ear. As a result, as distance between the alarm source and the intended listener increases, the perception of urgency in the alarm decreases. One of the benefits is that the alarm signal has an urgent quality only in the vicinity of the alarm, and the sense or urgency, i.e., the harshness, of the signal, decreases away from the source. Thus, the alarm is more noticeable at close ranges when needed, but is not objectionable at greater distances.

INDUSTRIAL APPLICABILITY

FIG. 3is a flow diagram of a method of the present invention and offers an illustration of application of the invention.

In a first control block302, an essentially rectangular pulse signal402is created. The pulse signal402has a desired period404, for example about 1 Hertz, and a desired first amplitude406, for example about 90 to 100 decibels.

In a second control block304, a shaped modulation component408is added to the pulse signal402from the desired first amplitude406to a desired second amplitude410to create a modulating waveform412. As an example, the desired second amplitude410may be about 10 decibels above the desired first amplitude406.

In a third control block306, a carrier signal414is created, having a period of, for example, about 1200 to 1300 Hertz.

In a fourth control block308, the carrier signal414and the modulating waveform412are combined to create an audible alarm signal416, as depicted inFIG. 4d.

In one embodiment, an ambient sound level is determined in a fifth control block310. Control may then proceed to a sixth control block312, in which the first and second amplitudes406,410are varied as a function of the ambient sound level, thus creating a less harsh alarm sound as the distance from the alarm source increases. Alternatively, fifth and sixth control blocks310,312may not be used, and the first and second amplitudes406,410may be fixed in value.

In a seventh control block314, a condition of a desired actuation of an alarm is determined. For example, it may be desired to actuate an alarm each time a vehicle or mobile machine is either in reverse mode or is actually moving in reverse. Other examples may include any time a vehicle or mobile machine is moving, proximity detection, intrusion alarms, fire alarms, warnings of imminent events such as blast warnings, condition alarms for medical and communications use, and the like.

In an eighth control block316, an audible alarm is actuated in response the determined condition of seventh control block314.

Other aspects can be obtained from a study of the drawings, the disclosure, and the appended claims.