Apparatus and method for designing sound compensation filter in portable terminal
A method and an apparatus for designing a sound compensation filter of a portable terminal are provided. The method includes synchronizing a signal input through a microphone of the system and a test signal, estimating a loss interval of the synchronized signal, compensating for a frame signal delayed by a signal loss in a time axis when the signal loss of the estimated loss interval is greater than a threshold and restoring the loss interval of the signal.
1. A method for restoring a compromised test signal in a sound compensation filter design system, the method comprising:
synchronizing a signal input through a microphone of the system and a test signal;
estimating a loss interval of the synchronized signal;
compensating for a frame signal delayed by a signal loss in a time axis when the signal loss of the estimated loss interval is greater than a threshold; and
restoring the loss interval of the signal.
2. The method of claim 1 , wherein the estimating of the loss interval comprises:
segmenting and dividing the synchronized signal into frames;
calculating a time average of all the frames in the segment;
conducting a Fast Fourier Transform (FFT) on the signal divided into the frames and the time average of the frames; and
estimating a signal loss interval in every segment and in every frame.
3. The method of claim 2 , further comprising extracting the frame signal delayed by the signal loss from the segmented signal.
4. The method of claim 1 , wherein the estimating of the loss interval comprises using a least squares method having a criterion based on the following equation:
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where y s l [n,m] denotes a signal synchronized with a recorded test signal, segmented in sequence, and divided into frames, a i l denotes a maximum harmonics order of an i-th segment, f s denotes a sampling frequency, f i l denotes an l-th harmonic frequency, φ i l denotes a phase of the l-th segment, N[n] denotes noise, n denotes a time index, m denotes a frame index, i denotes a segment index, l denotes a number of segments, T i denotes a frame length, and N i denotes a total number of harmonics.
5. The method of claim 1 , wherein the restoring of the loss interval of the signal comprises using a least squares method having a criterion based on the following equation:
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where y s,comp i [n,m] denotes a compensated signal, a i l denotes a maximum harmonics order of an i-th segment, f s denotes a sampling frequency, f i l denotes an l-th harmonic frequency, φ i l denotes a phase of the l-th segment, N[n] denotes noise, n denotes a time index, m denotes a frame index, i denotes a segment index, l denotes a number of segments, T i denotes a frame length, and N i denotes a total number of harmonics.
6. The method of claim 1 , further comprising:
designing a compensation filter using the restored test signal.
7. The method of claim 1 , wherein the threshold is determined on an experimental basis.
8. The method of claim 1 , wherein the signal input through the microphone of the system is output from one of a speaker of at least one of the system and another device.
9. An apparatus for restoring a compromised test signal in a sound compensation filter design system, the apparatus comprising:
a signal synchronizer for synchronizing a signal input through a microphone of the system and a test signal;
a loss interval estimator for estimating a loss interval of the signal input from the signal synchronizer;
a signal delay compensator for compensating for a frame signal delayed by a signal loss in a time axis when the signal loss of the loss interval estimated at the loss interval estimator is greater than a threshold; and
a loss signal restorer for restoring the loss interval of the signal input from the signal delay compensator.
10. The apparatus of claim 9 , wherein the loss interval estimator segments and divides the synchronized signal into frames, calculates a time average of all the frames in the segment, conducts a Fast Fourier Transform (FFT) on the signal divided into the frames and the time average of the frames, and estimates a signal loss interval in every segment and in every frame.
11. The apparatus of claim 10 , wherein the signal delay compensator extracts the frame signal delayed by the signal loss from the segmented signal.
12. The apparatus of claim 9 , wherein the loss interval is estimated using a least squares method having a criterion based on the following equation:
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where y s i [n,m] denotes a signal synchronized with a recorded test signal, segmented in sequence, and divided into frames, a i l denotes a maximum harmonics order of an i-th segment, f s denotes a sampling frequency, f i l denotes an l-th harmonic frequency, φ i l denotes a phase of the l-th segment, N[n] denotes noise, n denotes a time index, m denotes a frame index, i denotes a segment index, l denotes a number of segments, T i denotes a frame length, and N i denotes a total number of harmonics.
13. The apparatus of claim 9 , wherein the signal of the loss interval is restored using a least squares method having a criterion based on the following equation:
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l
f
s
n
+
ϕ
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l
)
-
y
s
,
comp
i
[
n
,
m
]
2
where y s,comp i [n,m] denotes a compensated signal, a i l denotes a maximum harmonics order of an i-th segment, f s denotes a sampling frequency, f i l denotes an l-th harmonic frequency, φ i l denotes a phase of the l-th segment, N[n] denotes noise, n denotes a time index, m denotes a frame index, i denotes a segment index, l denotes a number of segments, T i denotes a frame length, and N i denotes a total number of harmonics.
14. The apparatus of claim 9 , wherein a compensation filter is designed using the restored test signal.
15. The apparatus of claim 9 , wherein the threshold is determined on an experimental basis.
16. The apparatus of claim 9 , wherein the apparatus for restoring the compromised test signal comprises one of a computer, a measurement device, and a portable terminal.
17. The apparatus of claim 9 , wherein the signal input through the microphone of the system is output from a speaker of at least one of the system and another device.