Audio signal processing device and audio signal adjusting method

1. An audio signal processing device, comprising:

a gain determining circuit, receiving an analog audio signal, and determining a gain based on a difference between a predefined threshold and an amplitude of the analog audio signal in response to detecting that a current sampling amplitude of the analog audio signal is greater than the predefined threshold; and

an audio signal processing circuit, coupled to the gain determining circuit, receiving the analog audio signal and the gain, and attenuating the analog audio signal according to the gain to generate an output audio signal,

wherein the gain determining circuit determines whether the current sampling amplitude of the analog audio signal is greater than a maximum recorded value when the current sampling amplitude of the analog audio signal is greater than the predefined threshold; and

when the current sampling amplitude of the analog audio signal is greater than the maximum recorded value, the gain determining circuit updates the gain according to a difference between the current sampling amplitude and the predefined threshold and uses the current sampling amplitude to update the maximum recorded value.

2. The audio signal processing device according to claim 1 , wherein the gain determining circuit does not update the gain determined based on a previous sampling amplitude of the analog audio signal when the current sampling amplitude of the analog audio signal is not greater than the maximum recorded value.

3. The audio signal processing device according to claim 1 , wherein the gain determining circuit calculates an equation calculated value for updating the gain based on the current sampling amplitude when the current sampling amplitude of the analog audio signal is greater than the predefined threshold and the maximum recorded value, wherein an equation for calculating the equation calculated value is expressed as:

Ga= 1−( x−TH )* P

wherein Ga is the equation calculated value, x is the current sampling amplitude of the analog audio signal, TH is the predefined threshold, and P is an adjustment parameter.

4. The audio signal processing device according to claim 1 , wherein the gain determining circuit activates a first counter to start counting when the current sampling amplitude of the analog audio signal drops from greater than the predefined threshold to less than the predefined threshold; and

the gain determining circuit determines to increase the gain when the first counter counts to a first target value.

5. The audio signal processing device according to claim 4 , wherein after the first counter counts to the first target value, the gain determining circuit restores the gain to a predefined value when the gain determining circuit detects that the current sampling amplitude of the analog audio signal crosses a zero point.

6. The audio signal processing device according to claim 5 , wherein while the first counter is counting, the gain determining circuit resets the first counter to zero in response to detecting that the current sampling amplitude of the analog audio signal is greater than the predefined threshold.

7. The audio signal processing device according to claim 4 , wherein after the first counter counts to the first target value, the gain determining circuit activates a second counter to start counting; and

the gain determining circuit progressively increases the gain by a predefined interval until the gain is restored to a predefined value when the second counter counts to a second target value.

8. The audio signal processing device according to claim 7 , wherein while the gain determining circuit is progressively increasing the gain repeatedly by the predefined interval, the gain determining circuit determines whether the gain is greater than an equation calculated value in response to detecting that the current sampling amplitude of the analog audio signal is greater than the predefined threshold, wherein an equation for calculating the equation calculated value is expressed as:

Ga= 1−( x−TH )* P

wherein Ga is the equation calculated value, x is the current sampling amplitude of the analog audio signal, TH is the predefined threshold, and P is an adjustment parameter;

the gain determining circuit uses the equation calculated value to update the gain when the gain is greater than the equation calculated value; and

the gain determining circuit does not update the gain and resets the second counter to zero when the gain is less than the equation calculated value.

9. An audio signal adjusting method, comprising:

receiving an analog audio signal;

determining a gain based on a difference between a predefined threshold and an amplitude of the analog audio signal in response to detecting that a current sampling amplitude of the analog audio signal is greater than the predefined threshold; and

attenuating the analog audio signal according to the gain to generate an output audio signal,

wherein the step of determining the gain based on the difference between the predefined threshold and the amplitude of the analog audio signal in response to detecting that the current sampling amplitude of the analog audio signal is greater than the predefined threshold comprises:

determining whether the current sampling amplitude of the analog audio signal is greater than a maximum recorded value when the current sampling amplitude of the analog audio signal is greater than the predefined threshold; and

when the current sampling amplitude of the analog audio signal is greater than the maximum recorded value, updating the gain according to a difference between the current sampling amplitude and the predefined threshold and using the current sampling amplitude to update the maximum recorded value.

10. The audio signal adjusting method according to claim 9 , wherein the step of determining the gain based on the difference between the predefined threshold and the amplitude of the analog audio signal in response to detecting that the current sampling amplitude of the analog audio signal is greater than the predefined threshold further comprises:

not updating the gain determined based on a previous sampling amplitude of the analog audio signal when the current sampling amplitude of the analog audio signal is not greater than the maximum recorded value.

11. The audio signal adjusting method according to claim 9 , wherein the step of updating the gain according to the difference between the current sampling amplitude and the predefined threshold when the current sampling amplitude of the analog audio signal is greater than the maximum recorded value comprises:

calculating an equation calculated value for updating the gain based on the current sampling amplitude, wherein an equation for calculating the equation calculated value is expressed as:

Ga= 1−( x−TH )* P

wherein Ga is the equation calculated value, x is the current sampling amplitude of the analog audio signal, TH is the predefined threshold, and P is an adjustment parameter.

12. The audio signal adjusting method according to claim 9 , further comprising:

activating a first counter to start counting when the current sampling amplitude of the analog audio signal drops from greater than the predefined threshold to less than the predefined threshold; and

determining to increase the gain when the first counter counts to a first target value.

13. The audio signal adjusting method according to claim 12 , wherein the step of determining to increase the gain when the first counter counts to the first target value comprises:

after the first counter counts to the first target value, restoring the gain to a predefined value when detecting that the current sampling amplitude of the analog audio signal crosses a zero point.

14. The audio signal adjusting method according to claim 13 , further comprising:

while the first counter is counting, resetting the first counter to zero in response to detecting that the current sampling amplitude of the analog audio signal is greater than the predefined threshold.

15. The audio signal adjusting method according to claim 12 , wherein the step of determining to increase the gain when the first counter counts to the first target value comprises:

after the first counter counts to the first target value, activating a second counter to start counting; and

progressively increasing the gain by a predefined interval when the second counter counts to a second target value.

16. The audio signal adjusting method according to claim 15 , further comprising:

while progressively increasing the gain repeatedly by the predefined interval, determining whether the gain is greater than an equation calculated value in response to detecting that the current sampling amplitude of the analog audio signal is greater than the predefined threshold, wherein an equation for calculating the equation calculated value is expressed as:

Ga= 1−( x−TH )* P

wherein Ga is the equation calculated value, x is the current sampling amplitude of the analog audio signal, TH is the predefined threshold, and P is an adjustment parameter;

using an equation calculated value to update the gain when the gain is greater than the equation calculated value; and

not updating the gain and resetting the second counter to zero when the gain is less than the equation calculated value.