Electrical audio signal processing systems and devices – Loudspeaker feedback
Reexamination Certificate
1997-09-26
2001-05-15
Isen, Forester W. (Department: 2644)
Electrical audio signal processing systems and devices
Loudspeaker feedback
C361S689000, C361S679090
Reexamination Certificate
active
06233343
ABSTRACT:
BACKGROUND OF THE INVENTION
Electronic devices, such as notebook computers, are now being designed to operate with multi-media features such as those found in desktop units. In order for the user to have as enjoyable an experience as with desktops, the sound emanating from the notebook should present as full a harmonic content as the original sound. Most notebooks today currently are limited to not having frequencies generated below 150 Hz. Since most consumer audio equipment supports a frequency range of 20 Hz to 20 kHz, the full richness of the sound the user expects just is not present in notebook computers.
Notebook computers are limited in generating this low frequency content due to several factors. The first factor is that the space limitation in the product restricts how large a speaker may be used to replicate the sound. A second related factor is that lower frequencies need to move a large mass of air to be heard and there is little suitable volume in which to construct the air chamber that a speaker needs. A third factor is that due to the human ear's weak response to low frequency signals, more power is required to generate a lower frequency signal with an equivalent loudness compared to a signal greater than 150 Hz. More power reduces the battery life of the notebook computer or requires more expensive circuitry to implement than current designs.
Small electronic device makers such as notebook computer manufacturers or small handheld television producers continually fail to adequately provide a full, rich harmonic sound in their products.
SUMMARY OF THE INVENTION
A power adapter for an electronic device, such as a notebook computer, includes a speaker to generate low audio frequencies, such as below 150 Hz. The speaker can be mounted in a variety of arrangements, i.e. closed-box, bass-reflex, or a more intricate shape which adds resonance (poles and zeros) to the acoustic filtering properties of the enclosure. An exemplary bass-reflex mounting includes a driver with resonance at 140 Hz, a chamber size of 7.74 in
3
and a port determined by Thiele-Small equations. This gives a low frequency response beginning at 70 Hz. This low frequency component is combined in free space with the higher frequency components emanating from the portable electronic device's internal speaker(s). The audio signal connection can be made when the AC adapter is connected to the notebook computer by using two additional wires in the power cord. Since users generally carry their AC adapters with them, they can enjoy full harmonic sound without taking anything extra along. Alternatively, the AC adapter and electronic device can contain additional circuitry to provide wireless paths for either the power distribution path or audio interface or both.
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Journal of the Audio Engineering Society May 1971, vol. 19, No. 5, “Loudspeakers in Vented Boxes: Part I” Author A. N. Thiel.
Journal of the Audio Engineering Society Jun. 1971, vol. 19, No. 6, “Loudspeakers in Vented Boxes: Part II” Author A. N. Thiel.
Hickman Scott N
Muranami Masahiko
Hewlett--Packard Company
Isen Forester W.
Myers Timothy F.
Pendleton Brian Tyrone
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