Electrical audio signal processing systems and devices – Including frequency control – Having automatic equalizer circuit
Reexamination Certificate
1997-09-08
2001-02-27
Nguyen, Duc (Department: 2743)
Electrical audio signal processing systems and devices
Including frequency control
Having automatic equalizer circuit
C381S102000, C381S107000
Reexamination Certificate
active
06195438
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates in general to the audio output of a receiver. More particularly, the invention relates to an apparatus and method for maintaining a substantially level audio output and controlling the tone of the audio output in an audio or audio-visual system.
Examples of audio and/or visual systems include: radios, televisions, tape players, digital tape players, compact disc (CD) players, and digital video disc (DVD) players. Examples of televisions include: analog NTSC television receivers, digital TV receivers or advanced television receivers, and the like. The present invention may also be incorporated in audio encoding or decoder devices.
The loudness of the audio output from a television receiver often changes from program to commercial on a given channel, from program to program on a given channel, and from channel to channel. Additionally, many television programs and most motion pictures intentionally vary the loudness from scene to scene to simulate how the sounds would be experienced in real life. For example, the sound of a gun shot or a cheering crowd at a football game is louder than the sound of two people having a face-to-face conversation in a room.
However, such real life loudness variations, while having some value in a movie theater, are often a source of annoyance when viewing a television program at a relatively close range in a relatively confined area. In an effort to correct this annoyance, some television manufacturers have incorporated automatic volume leveling (AVL) circuitry in their televisions. Such AVL circuits are similar to analog leveling circuitry found in various audio products such as tape recorders. While these analog AVL circuits provide some relief from loudness variations, they generally suffer from having a limited volume hold time for quiet passages, and slow attach and decay (release) times constants. In addition, the AVL circuitry raises the cost of the television.
In addition, the level of loudness perceived by humans varies considerably depending on the frequency and amplitude of the sound. When comparing music in a concert hall with music in a home environment, the music will not sound the same to the listener, even though the frequency spectrum is exactly the same but at a different sound or amplitude level. In particular, the ear is less sensitive to low and high frequencies at low sound levels. This justifies increasing the bass-treble settings for musical sources in the home setting.
Certain conventional systems may have sound equalizers built in for adjusting the bass-treble controls of the system. For listening to the musical contents with conventional systems, the bass-treble settings may be increased to make the music contents sound more realistic. However, for vocal contents, a decrease in the bass and treble settings results in a better signal to noise ratio. An automatic equalizer device alters the source frequency spectrum by automatically adjusting the bass-treble settings depending on the program source.
Accordingly, it would be advantageous to provide an automatic audio leveling and source frequency spectrum equalizing apparatus and method that would provide an infinite hold time for quiet passages, fast and precise attack and decay times, and frequency spectrum adjustments, which would not require additional circuitry.
BRIEF SUMMARY OF THE INVENTION
Thus, it is an object of the present invention to provide a low cost method and apparatus for maintaining a substantially constant audio output and for automatically adjusting the tone of the sound from a receiver.
It is another object of the present invention to provide a method and apparatus capable of relatively fast and precise response times in maintaining a substantially constant audio output and the desired tone from a receiver.
It is yet another object of the present invention to provide a method and apparatus capable of maintaining a substantially constant audio output from a receiver during quiet passages.
It is still another object of the present invention to provide a precise, efficient, reliable, and easily implemented method and apparatus for maintaining a substantially constant audio output from a receiver.
These and other objects are realized in accordance with the present invention by providing a microcomputer for automatically controlling an audio output from a receiver. The microcomputer calculates a power signal corresponding to the power of a detected audio input signal, determines whether the calculated power signal is above or below a predetermined power value, generates a power control signal in response to whether the calculated power signal is above or below the predetermined value, and uses the power control signal to automatically control the receiver's audio output and maintain a substantially constant audio output.
In another embodiment, the method and apparatus of the present invention is implemented as a detection circuit in communication with a microcomputer. The detection circuit calculates a power signal corresponding to the power of a detached audio input signal. The microcomputer determines whether the calculated power signal is above or below a predetermined power value, generates a power control signal in response to whether the calculated power signal is above or below the predetermined value, and uses the power control signal to automatically maintain a substantially constant audio output from the receiver.
Accordingly, the present invention achieves several advantages. In particular, when the receiver is a television, the method and apparatus of the present invention saves manufacturing costs and complexity by incorporating its audio leveling operations into the microcomputer that is already present in most current televisions. The speed and precision of the computer-implemented present invention is superior to prior art analog audio leveling circuits, thereby decreasing response times, allowing quiet passages to be maintained indefinitely, and allowing the necessary audio adjustments to be made in real time.
It is a further object of the present invention to combine the audio leveling function with an automatic audio spectrum equalizing function into a single integrated microprocessor controlled system.
The present invention also uses the microcomputer to control the tone and volume of an audio or audio-visual system, which microcomputer is interfaced with optional pre-processing circuitry. In particular, a microcomputer may function to control the bass-treble settings and volume of audio signals in such a system controlled by a volume and tone control. As a variation, the present invention may use the microcomputer to control the tone and volume of an audio or audio-visual system without optional pre-processing circuitry, wherein the audio signals are amplified and processed by the microcomputer to control the bass-treble settings and volume of the audio signals.
Accordingly, the present invention digitally processes audio signals of an audio or audio-visual system to automatically adjust the sound output characteristics of the system, by automatically leveling the volume of audio signals; and altering a source frequency spectrum of the audio signals by automatically adjusting equalizer settings depending on the content of the source frequency spectrum, wherein a substantially constant volume and an equalized frequency spectrum is maintained in the sound of the audio or audio-visual system.
In particular, the present includes a method of digitally processing audio signals of an audio or audio-visual system to automatically adjust the sound output characteristics of the system by summing audio signals from multiple audio channels; sampling the summed audio signals at a first sampling rate for use in leveling the volume of the summed audio signals; sampling the summed audio signals at a second sampling rate for equalizing the source spectrum of the summed audio signals, wherein the second sampling rate is higher than the first sampling rate; processing the summed audio signals sampled
Rzeszewski Theodore S.
Yumoto Hideki
Matsushita Electric Corporation of America
McDermott & Will & Emery
Nguyen Duc
LandOfFree
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