Communications: electrical – Audible indication – Diaphragm
Reexamination Certificate
1999-10-22
2001-04-10
Mullen, Thomas (Department: 2632)
Communications: electrical
Audible indication
Diaphragm
C340S388400, C340S391100
Reexamination Certificate
active
06215391
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention is directed to a buzzer assembly for use in a personal communications device which changes geometry in order to emit sounds at a variety of frequencies at an approximately constant volume, such as for playing melodic alerts.
Personal communications devices, such as cellular phones or pagers, typically have a number of components which help to alert the user to various conditions. For instance, an alert may be generated in response to an incoming call or page. The most common alert generating components are vibrators and buzzers, of which buzzers are of interest for the present invention.
Typically, buzzers resonate at a ring frequency around three kilohertz, producing a simple monotone alert sound or a dual tone of closely spaced frequencies. Problems arise when, instead of a simple monotone, users desire alert sounds to be other than monotone or tightly spaced dual tone, such as a melody that varies frequency over the range from about 1 kHz to about 4 kHz. Typically, buzzers are configured for optimum audio output at a particular frequency (the “ring frequency”). When such a buzzer is used at other frequencies, the buzzer output volume drops off significantly, even at frequencies as close as 200 Hz away from the ring frequency. This results in an unrecognizable melody with significant disparities in volume while the “melody” is played. This variability in loudness reduces the perceived quality, can be annoying to the user, and may result in missed calls.
The immediately apparent solution of using a larger buzzer capable of generating sufficient volume at different frequencies is not practical due to the extreme space constraint pressures present in today's world of ever shrinking personal communications devices.
It is known in the art to combine a vibrator, speaker and buzzer into one unit, called a multi-mode actuator. While such multi-mode actuators can be used to play melodies, they suffer from a serious drawback. The output from the multi-mode actuator in speaker mode should be directed into the user's ear for optimum performance. However, because the audio volume in call alert mode is much higher than in speaker mode, the output of the multi-mode actuator should not be directed into the user's ear. Thus, the optimum output routing configuration for the multi-mode actuator is different for its different functions, thereby defeating its combinational advantage. As such, it is common to use a separate buzzer whose output is typically vented perpendicular to the plane of the speaker that is used to output audio signals from the personal communications device. In this manner, the output from the buzzer is not directed into the user's ear in the event a user places the device against their ear immediately prior to an alert. However, due to existing buzzers' inherent output audio volume variation over frequency, as mentioned above, existing buzzers perform poorly when asked to play melodies, rather than a monotone, for alert signals.
As such, there remains a need for an improved buzzer assembly for use with portable communications devices that produces an acceptable level of audio volume across a broader frequency range, so as to be able to play melodies and the like for alert signals.
SUMMARY OF THE INVENTION
The buzzer assembly of the present invention includes a combined gasket and buzzer that change geometry and thereby change acoustic impedance at different audio frequencies. The change in acoustic impedance or acoustic load of the buzzer diaphragm changes the resonant frequency of the buzzer assembly. When the buzzer is then operated at or near resonant frequency corresponding to the then-current acoustic impedance, the sound generated by the buzzer assembly is louder. By changing the resonant frequency of the buzzer assembly in this manner to correspond to the frequency of the tone to be generated, the sound volume generated by the buzzer assembly can be augmented across a frequency range that may be 3 kHz or larger. When augmented in such a fashion, the audio output from the buzzer assembly is approximately constant across a larger frequency range than with conventional buzzer solutions, and preferably across the entire range frequency range of 1 kHz to 4 kHz.
One preferred embodiment of the buzzer assembly includes a conventional buzzer slidably mounted in a set of guide rails. A translational actuator, in this case a solenoid, is operatively connected to the buzzer so as to slide the buzzer within the guide rails. The output port of the buzzer is sealed against an expandable buzzer gasket which is also sealed against the output port of the communications device. By moving the buzzer with the solenoid, the volume of air within the expandable buzzer gasket changes, thereby changing the acoustic impedance seen by the buzzer. This change in acoustic impedance effectively changes the resonant frequency of the buzzer and allows different frequencies to be created by the buzzer assembly at comparable audio volume levels. The mechanical action of the solenoid is controlled by a suitable control circuit that interfaces with the balance of the personal communications device to cause the buzzer assembly to create alert signals that are melodies or the like, based on stored instructions. By dynamically changing the current acoustic impedance of the buzzer, and therefore the current resonant frequency of the buzzer, to correspond to the desired audio frequency, the buzzer assembly can create audio sounds of different frequencies at comparable volume levels. The buzzer assembly preferably outputs a relatively consistent volume across the frequency range of 1-4 kHz, thereby covering two octaves.
An alternative embodiment does not move the buzzer, but rather changes the volume of air within the gasket through the use of a variable geometry deformable gasket. The deformable gasket may include one or more piezo-electric films that change shape in response to various electrical currents. By changing the internal shape of the buzzer gasket, but keeping the buzzer stationary, the buzzer assembly may still change its resonant frequency by changing the acoustic impedance seen by the buzzer.
Another alternative embodiment uses a gasket of a fixed size, but includes an extra chamber acoustically communicating with the interior of the gasket. The volume of this extra chamber is changed by means of a translational actuator attached to a piston within the extra chamber. The change in volume of the extra chamber likewise changes the resonant frequency of the buzzer assembly and allows different frequencies to be created by the buzzer assembly at comparable volume levels.
Yet another embodiment uses a conventional gasket, but changes the size of the chamber within the buzzer itself, thereby changing the resonant frequency of the buzzer assembly.
REFERENCES:
patent: 4413253 (1983-11-01), Hofer et al.
patent: 4728933 (1988-03-01), Mazza
patent: 5953408 (1999-09-01), Blanvillain et al.
patent: 6075998 (2000-06-01), Morishima
patent: 86292 (1979-07-01), None
patent: 75578 (1994-03-01), None
Johnsen Ronald J.
Murray Matthew J.
Coats & Bennett PLLC
Ericsson Inc.
Mullen Thomas
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