Process of implementing low frequency of audio signal

Abstract

A process of implementing a low frequency of an audio signal includes the steps of collecting a fundamental frequency from the audio signal at a low frequency region thereof, generating a controlled 2nd harmonic, a controlled 3rd harmonic, and a controlled 4th harmonics respectively based on a 2nd harmonic, a 3rd harmonic, and a 4th harmonic in responsive to the fundamental frequency, and generating a final output signal from a combination of the controlled 2nd harmonic, the controlled 3rd harmonic, and the controlled 4th harmonic. In which, the output signal is generated correlating with a loudness of the fundamental frequency to enhance the bass performance of an audio system device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating the process of implementing a low frequency of an audio signal according to a preferred embodiment of the present invention.

Claims

1. A process of implementing a low frequency region of an audio signal, comprising the steps of: (a) collecting a fundamental frequency from said audio signal at a low frequency region thereof;(b) deriving a first control signal in responsive to dynamirange of said fundamental frequency;(c) generating a 2nd harmonic, a 3rd harmonic, and a 4th harmonic correlating with said fundamental frequency;(d) generating a controlled 2nd harmonic, a controlled 3rd harmonic, and a controlled 4th harmonics respectively based on said 2nd harmonic, said 3rd harmonic, and said 4th harmonic in responsive to said fundamental frequency; and(e) generating a final output signal from a combination of said controlled 2nd harmonic, said controlled 3rd harmonic, and said controlled 4th harmonic, wherein said final output signal is correlating with a loudness of said fundamental frequency.

2. The process, as recited in claim 1, wherein the step (c) further comprises the steps of: (c.1) self-multiplying said fundamental frequency to form said 2nd harmonic,(c.2) multiplying said 2nd harmonic by said first control signal to form a time-varying gain controlled 2nd harmonic;(c.3) multiplying said time-varying gain controlled 2nd harmonic by said fundamental frequency to form said 3rd harmonic;(c.4) multiplying said 3rd harmonic by said first control signal to form a time-varying gain controlled 3rd harmonic;(c.5) multiplying said time-varying gain controlled 3rd harmonic by said fundamental frequency to form said 4th harmonic;(c.6) multiplying said 4th harmonic by said first control signal to form a time-varying gain controlled 4th harmonic.

3. The process as recited in claim 1 wherein, in the step (d), said controlled 2nd harmonic, said controlled 3rd harmonic, and said controlled 4th harmonic are formed by processing said 2nd harmonic, said 3rd harmonic, and said 4h harmonic through an automatic gain control module.

4. The process as recited in claim 2 wherein, in the step (d), said controlled 2nd harmonic, said controlled 3rd harmonic, and said controlled 4th harmonic are formed by processing said 2nd harmonic, said 3rd harmonic, and said 4th harmonic through an automatic gain control module.

5. The process, as recited in claim 4, wherein the step (e) further comprises the steps of: (e.1) adding said controlled 3rd harmonic with said controlled 4th harmonic to form a first transitional output signal;(e.2) filtering out a frequency corresponding to said fundamental frequency and said 2nd harmonic from said first transitional output signal to form a second transitional output signal, wherein said second transitional output signal is added to said controlled 2nd harmonic to form a third transitional output signal;(e.3) multiplying said low frequency by said first control signal to form a controlled low frequency, wherein said controlled low frequency is added to the said third transitional output signal to form a fourth transitional output signal; and(e.4) filtering said fourth transitional output signal through a bandpass filter to form said final output signal.

6. The process as recited in claim 1 wherein, in the step (d), said controlled 2nd, 3rd, and 4th harmonics are generated from said 2nd, 3rd, and 4th harmonics by attenuation process to maintain said controlled 2nd, 3rd, and 4th harmonics at the same level of loudness of said fundamental frequency.

7. The process as recited in claim 5 wherein, in the step (d), said controlled 2nd, 3rd, and 4th harmonics are generated from said 2nd, 3rd, and 4th harmonics by attenuation process to maintain said controlled 2nd, 3rd, and 4th harmonics at the same level of loudness of said fundamental frequency.

8. The process, as recited in claim 1, wherein the step (b) further comprises a step of detecting an energy level of said fundamental frequency by an envelope signal detector to characterize said energy of said fundamental frequency as envelope signal so as to control said energy of each of said 2nd,3rd, and 4th harmonics.

9. The process, as recited in claim 7, wherein the step (b) further comprises a step of detecting an energy level of said fundamental frequency by an envelope signal detector to characterize said energy of said fundamental frequency as envelope signal so as to control said energy of each of said 2nd, 3rd, and 4th harmonics.

10. The process, as recited in claim 1, further comprising the steps of: setting a cut-off point to said fundamental frequency to collect a transitional signal which is out of said cut-off point;generating a second control signal; andprocessing said transitional signal with said second control signal to combine with said controlled 2nd, 3rd, and 4th harmonics to form said final output signal.

11. The process, as recited in claim 9, further comprising the steps of: setting a cut-off point to said fundamental frequency to collect a transitional signal which is out of said cut-off point;generating a second control signal; andprocessing said transitional signal with said second control signal to combine with said controlled 2nd, 3rd, and 4th harmonics to form said final output signal.

12. The process, as recited in claim 1, wherein the steps (c) and (d) controls said energy of said fundamental frequency at a condition that when said fundamental frequency is within 300Hz, an energy dynamirange of said 2nd harmonic is 1˜1.5 times of said fundamental frequency, an energy dynamirange of said 3rd harmonic is 1.5˜2 times of said fundamental frequency, and an energy dynamirange of said 4th harmonic is 2˜2.5 times of said fundamental frequency.

13. The process, as recited in claim 11, wherein the steps (c) and (d) controls said energy of said fundamental frequency at a condition that when said fundamental frequency is within 300 Hz, an energy dynamirange of said 2nd harmonic is 1˜1.5 times of said fundamental frequency, an energy dynamirange of said 3rd harmonic is 1.5˜2 times of said fundamental frequency, and an energy dynamirange of said 4th harmonic is 2˜2.5 times of said fundamental frequency.

14. An audio enhancing system for enhancing a low frequency of an audio signal, comprising: a first filtering device filtering out a low frequency signal from said audio signal to obtain a fundamental frequency from said audio signal at a low frequency region thereof;an automatic gain control module generating a first control signal, wherein a 2nd harmonic, a 3rd harmonic, and a 4th harmonic are generated correlating with said fundamental frequency;first means for processing said 2nd harmonic, a 3rd harmonic, and a 4th harmonic, wherein a controlled 2nd harmonic, a controlled 3rd harmonic, and a controlled 4th harmonic are generated respectively based on said 2nd harmonic, said 3rd harmonic, and said 4th harmonic in responsive to said fundamental frequency; andsecond means for generating a final output signal from a combination of said controlled 2nd harmonic, said controlled 3rd harmonic, and said controlled 4th harmonic, wherein said final output signal is correlating with a loudness of said fundamental frequency.

15. The audio enhancing system, as recited in claim 14, wherein said first means comprises a multiplier processing said fundamental frequency that said fundamental frequency is processed to self-multiply to form said 2nd harmonic, said 2nd harmonic is processed to multiply by said first control signal to form a time-varying gain controlled 2nd harmonic, said time-varying gain controlled 2nd harmonic is processed to multiply by said fundamental frequency to form said 3rd harmonic, said 3rd harmonic is processed to multiply by said first control signal to form a time-varying gain controlled 3rd harmonic, and said time-varying gain controlled 3rd harmonic is processed to multiply by said fundamental frequency to form said 4th harmonic.

16. The audio enhancing system, as recited in claim 15, wherein said second means comprises a processor adding said controlled 3rd harmonic with said controlled 4th harmonic to form a first transitional output signal, a first filter filtering out said fundamental frequency and said 2nd harmonic from said first transitional output signal to form a second transitional output signal, wherein said second transitional output signal is added to said controlled 2nd harmonic to form a fourth transitional output signal, a multiplying processor multiplying said fundamental frequency by said first control signal to form a controlled fundamental frequency, wherein said controlled fundamental frequency is added to the said fourth transitional output signal to form a fifth transitional output signal, and a second filter filtering said fifth output signal through a bandpass filter to form said final output signal.

17. The audio enhancing system, as recited in claim 16, wherein said controlled 2nd, 3rd, and 4th harmonics are generated from said 2 nd, 3rd, and 4th harmonics by attenuation process to maintain said controlled 2nd, 3rd, and 4th harmonics at the same level of loudness of said fundamental frequency.

18. The audio enhancing system, as recited in claim 17, further comprises an envelope detector detecting an energy level of said fundamental frequency to characterize said energy of said fundamental frequency as envelope signal so as to control said energy of each of said 2nd, 3rd, and 4th harmonics.

19. The audio enhancing system, as recited in claim 14, wherein said energy of said fundamental frequency is controlled at a condition that when said fundamental frequency is within 300 Hz, an energy dynamirange of said 2nd harmonic is 1˜1.5 times of said fundamental frequency, an energy dynamirange of said 3rd harmonic is 1.5˜2 times of said fundamental frequency, and an energy dynamirange of said 4th harmonic is 2˜2.5 times of said fundamental frequency.

20. The audio enhancing system, as recited in claim 18, wherein said energy of said fundamental frequency is controlled at a condition that when said fundamental frequency is within 300 Hz, an energy dynamirange of said 2nd harmonic is 1˜1.5 times of said fundamental frequency, an energy dynamirange of said 3rd harmonic is 1.5˜2 times of said fundamental frequency, and an energy dynamirange of said 4th harmonic is 2˜2.5 times of said fundamental frequency.