ALARM

Abstract: Fire alarm for persons with impaired hearing including an activating smoke detector and a loudspeaker that is driven by a sound circuit including amplifier and a sound generating part. The sound generating part is so programmed that it delivers both square waves and sawtooth waves with different frequencies below or at 500 Hz. The result is a very powerful wobbling alarm sound that can be heard of the majority of persons with impaired hearing. In many cases also vibrations that are generated by the alarm can be "felt" in other ways than by hearing, in particular by different objects being oscillated.

Description: Alarm In order to secure that also deaf or persons with reduced hearing are warned when there is a fire it is known to use a flashing fire alarm. If you look in another direction or maybe even sleep the probability that you do not discover a flashing light is large, as at strong sunlight. It is further known to use vibrators, that are worn in the pocket and that are activated wireless at alarm. To remember always to transfer a vibrator when one changes clothes is not that easy and to put it under the pillow when sleeping do not guarantee that you notice it since it may move somewhat during sleep. Furthermore this type of alarm can only be used where there exist a transmitter that can activate the vibrator, in other words the alarm is normally only active in the home environment of the person with impaired hearing and it is furthermore expensive. Additionally, always to remember the vibrator, that hopefully never will be used, is in reality an impossibility. As is realized these alarm possibilities are not as efficient as the penetrating sound signals from ordinary fire alarms are for those who hear. In order to make life safer for persons with impaired hearing there exist a need for better alarm possibilities for those with impaired hearing. The object of the invention is to achieve this object. In accordance with the invention this object is solved with an alarm with a sound signal. An alarm with a sound signal may seem improbable for persons with impaired hearing, but since the majority of persons with impaired hearing has the reduction in the high or middle area low tones can be used that are audible for the majority of those with impaired hearing. In order further to improve the possibility for persons with impaired hearing to hear and recognize the alarm a square wave shape is used, for instance a frequency of 100, one on 200, one on 300 and one on 500Hz may be mixed. Since it is a square wave and in the frequency area up to 500Hz it is possible to use a sufficiently powerful sound in order to make the sound audible also to persons with impaired hearing in this frequency area, at the same time as it is possible to stay below the pain threshold level for persons with ordinary hearing. By further, in addition to feeding the loudspeaker with square wave shaped pulses, also add one or several signals with sawtooth shape and a low frequency, for instance coinciding with those of the square wave, a corresponding additional sound is obtained in the low frequency area facilitating the hearing for persons with impaired. One can also consider to allow the sawtooth wave or waves to have a slightly differing frequency as compared to that of the square wave so that one also obtain an interference that result in a variation in amplitude and shape for the different sound pulses, or tones. In this way the adaptability of the ear is eliminated. With adaptability is here ment the ability of the ear to cut out a continuous tone or other sound so that it is not noticed. By the use of a sawtooth shape for the interfering additional sound wave a greater variation in the sound is achieved and the probability for a person with impaired hearing to hear and notice it increases. Since furthermore low tones are used there is also the possibility at lucky circumstances that different objects in the room can be induced to vibrate and through their vibration can bring the alarm to the attention of a person with impaired hearing even if he or she can not hear the alarm. For person with that impaired hearing it is however appropriate also to use light or vibrator alarm to increase the safety. By, in a preferable further development of the inventive thought, providing the alarm with a discharge flashlight there is in the usual way the possibility for a person that cannot hear at all to see the alarm and for a person with faint hearing it is possible to get confirmation that it is the alarm he or she is hearing. Further advantages of the invention as well as further developments of this is apparent from the claims as well as the following description of a preferred embodiment of the invention shown in the enclosed drawings. In these fig 1 shows an alarm in accordance with the invention in a top view and fig 2 the same device seen from an end. The alarm shown in fig 1 includes a battery unit 1 , an electronic sound circuit with an amplifier 2, a smoke detector and a flashlight 4. The amplifier 2 is connected to a loudspeaker 5 to which is added a resonator 6 comprising a cylindric tube with a diameter corresponding to the outlet opening of the loudspeaker and extending axially out from the loudspeaker. The resonator tube provides together with the depth of the loudspeaker a suitable resonance length for one of the desired frequencies. In front of the opening of the resonator tube in the end opposed to that of the loudspeaker end a loudspeaker grid 7 is arranged. The fire alarm shown in the drawings function in such a manner that at a possible fire the smoke detector 3, that preferably is of ionization type, in order to ascertain a long time of use, detect the smoke. The smoke detector 3 activates the flashlight and the sound circuit with its loudspeaker. The amplifier feeds the loudspeaker with a signal in accordance with the invention. The signal consist of square waves mixed with sawtooth waves and a wobbling hard sound. The square wave in itself sound approximately as a net frequency buzz from a poorly fastened apparatus but with a higher frequency, while the saw tooth wave gives more normal tone. When put together the varying and easily recognizable alarm signal is obtained that does not risk to be confused with the buzzing from a refrigerator or the like. By the use of the resonator a considerable gain is obtained for the sounds or tones that are of interest from a hearing point of view for persons with impaired hearing. This increase is apparent from the enclosed table that has been measured for an alarm sound in accordance with the invention. As is apparent from the table the straight cylindrical shown resonator tube can be exchanged for an outward from the loudspeaker slightly conically converging tube, at which a certain additional gain is obtained for the interesting frequencies. Recalculated to a maximum power of 10W fed to the loudspeaker element this means that the sound pressure levels i the 50Hz-octave at a distance of lm would be in the size order 95dB. The conical resonator gives somewhat higher sound pressure levels than the straight in the 500Hz band and somewhat lower in the 1000-2000Hz band. From the point of hearing the 500Hz band is the most important, which is apparent from a comparison of the sound providers sound levels in relation to the threshold values in the column most to the right. As is apparent the measured sound levels at 500Hz mean 75 - 79dB over the normal hearing threshold while at 250Hz the above values are 49 - 61dB over a normal hearing threshold. At a free propagation of the sound the sound level is reduced with 6dB at every doubling of the distance. Indoors the sound level is less reduced due to reflexes in floor, roof etc. The maximum sound level at ca. 10m distance with a nominal power feed of 10W will be at least 75-80dB SPL in the 500Hz-band. In other words the signal can be appreciated to be well audible for persons with impaired hearing of 50dB at 500Hz. Thus the signal can be registered by the majority of all persons with impaired hearing, since the dominating types of hearing damages means comparatively well preserved hearing thresholds in the low frequency area. The electric signals, that is in particular the electric square pulses and sawtooth pulses that are made and mixed in the sound circuit and amplified with the connected amplifier and resonator may either be stored digitally as a recorded and tested sound sequence, that is then played over and over again at activation or as mathematical functions for the voltage pulses or current signals that the loudspeaker is fed with. In the present case the sawtooth shape as well as the square shape are symmetric. Within the frame of the inventive thought one can also consider at alarm to vary the frequency either for square wave or sawtooth wave so that a varied frequency is obtained in the wobbling of the sound which further reduces the risk that the sound seems continuous and therefor is missed. At an output level of 10W of the alarm the alarm can be activated and heard for a long time when sounding and with a high sound level even with a moderate battery size. The above described device is intended to be arranged as an individual fire alarm, for instance at the home of a person with reduced hearing. Within the frame of the invevenntive thought the used sound frequencies can be varied in different ways and be tested to obtain the best possible hearability for persons with impaired hearing. In the extreme case one can also consider that a person with impaired hearing may have his own alarm signal developed if he has difficulties to hear the normal alarm signal for persons with impaired hearing. Preferably however the alarm signal should be comparatively normalized so that a person with impaired hearing may realize that it is a fire alarm or other alarm he is hearing independent of if he is at home, at a hospital etc. The invention provide in relation to the known and used alarms improved safety for the majority, and a cost per alarm device that is only a fraction of the cost for a vibrator alarm device. Table Sound levels at a distance of one meter straight in front and 90° from the side in an echo free measuring room. The sound pressure level is given in dB re. 20 μPa for an electric signal voltage to the loudspeaker of IN RMS.

Claims: CLAIMS 1. Alarm, in particular fire alarm for persons with impaired hearing, characterized in that it delivers sound constituted by one or several square waves and one or several sawtooth waves. 2. Alarm according to claim 1, characterized in that the frequency of the square waves are in the area 100 - 500Hz. 3. Alarm according to any of the preceding claims, characterized in that the square waves are symmetric. 4. Alarm according to any of the preceding claims, characterized in that for square waves and/or sawtooth waves the frequencies are 100, 200, 300 and 500 Hz. 5. Alarm according to any of the preceding claims, characterized in that in front of a sound generating loudspeaker a resonator is arranged with such length that a gain is obtained in a low frequency area. 6. Alarm according to claim 5, characterized in that the resonator is conically narrowing from the loudspeaker. 7. Alarm according to any of the preceding claims, characterized in that it is provided with a flashlight to enable control of if a heard alarm is correct or not. 8. Alarm according to any of the preceding claims, characterized in that one or several frequencies of sawtooth waves or square waves are varied when sound is generated. 9. Alarm according to any of the preceding claims, characterized in that it is integrated with a smoke detector and powered by batteries so that it in a known manner can be suspended in the roof. 10. Alarm according to any of the preceding claim, characterized in that the alarm sound is a digitally recorded and stored sound.

Inventors: KOBUSINSKI KARL, KOBUSINSKI, KARL
Applicants: KOBUSINSKI KARL, KOBUSINSKI, KARL
Application year: 2000
Main classification: G08B17
IPC codes: G08B1, G08B3, G08B17, G08B23