Method and system for measuring a system's transmission quality

• US 20050159944A1
• Filed: 02/26/2003
• Published: 07/21/2005
• Est. Priority Date: 03/08/2002
• Status: Active Grant

• Current Assignee: Koninklijke KPN NV
• Original Assignee: Koninklijke KPN NV
• Inventors: Beerends, John Gerard
• Granted Patent: US 7,689,406 B2
• Time in Patent Office: Days
• US Class Current: 704/225
• CPC Class Codes: G10L 25/69 for evaluating synthetic or decoded voice signals

Abstract

Method and system for measuring the transmission quality of an audio transmission system, an input signal (X) being entered into the system, resulting in an output signal (Y), output by the system, both signals, the input signal and the output signal, being mutually processed, the method comprising that the output signal and/or the input signal of the system under test are scaled in a way that small deviations of the power are compensated, while larger deviations are compensated partially, dependent on the power ratio. An artificial reference speech signal may be created, for which the noise levels as present in the original input speech signal are lowered by a scaling factor that depends on the local level of the noise in this input.

Claims

1. Method for measuring the transmission quality of an audio system, an input signal (X) being entered into the audio system, resulting in an output signal (Y), output by the audio system, the input signal and the output signal being processed preferably compared, comprising that the output signal and/or the input signal of the audio system are scaled in a way that small deviations of the power are compensated, while larger deviations are compensated partially, dependent on the power ratio.

2. Method according to claim 1, comprising that

a compensation ratio F is calculated from the power representations PX and PY resp. of said input signal (X) and output signal (Y), F being equal to the ratio PX/PY;

a clipped ratio C being calculated, C being equal to a first clipping value mm for F<

mm, or C being equal to a second clipping value MM for F>

MM, or otherwise C being equal to F;

a softscale ratio S being calculated from a first scaling factor m and a second scaling factor M, with mm<

m≦

1 and MM>

M≧

1, S being equal to C^a+C−

C(m)<sup>a−

1</sup> for C<

m, ‘

a’

being a first tuning parameter being set to a value>

0 and<

1, or S being equal to C^a+C−

C(M)<sup>a−

1</sup> for C>

M, or otherwise S being equal to C.

3. Method according to claim 1, comprising that an artificial reference speech signal is created, for which the noise levels as present in the original input speech signal are lowered by a scaling factor that depends on the local level of the noise in this input.

4. Method according to claim 3, comprising that the difference D(f)n in internal representations LX(f)n and LY(f)n resp. of said input signal (X) and output signal (Y) in the time-frequency plane is set to be equal to |LY(f)n−

LX(f)n^b/K<sup>b−

1</sup>| for LX(f)n<

K, or to be equal to |LY(f)n−

LX(f)n| for LX(f)n≧

K, b being a second tuning parameter being set to a value>

1 and K being a low level noise power criterion value, representing a desired low level noise power criterion.

5. Method according to claim 3, comprising that a difference D(f)n in internal representations LX(f)n and LY(f)n resp. of said input signal (X) and output signal (Y) in the time-frequency plane is set to be equal to |LY(f)n−

LX(f)n^b/K<sup>b−

1</sup>| for LX(t)<

K′

or be equal to |LY(f)n−

LX(f)n| for LX(t)≧

K′

, b being a second tuning parameter being set to a value>

1 and K′

being a low level noise power criterion value, representing the desired low level noise power criterion.

6. System for measuring the transmission quality of an audio system, an input signal (X) being entered into the audio system, resulting in an output signal (Y), output by the audio system, the input signal and the output signal being mutually processed preferably compared, comprising scaling means for scaling the output signal and/or the input signal of the audio system in a way that small deviations of the power are compensated, while larger deviations are compensated partially, dependent on the power ratio.

7. System according to claim 6, comprising means for calculating a compensation ratio F from the power representations PX and PY resp. of said input signal (X) and output signal (Y), F being equal to the ratio PX/PY;

comprising means for calculating a clipped ratio C, being equal to a first clipping value mm for F<

mm, or C being equal to a second clipping value MM for F>

MM, or otherwise C being equal to F; and

comprising means for calculating a softscale ratio S from a first scaling factor m and a second scaling factor M, with mm<

m≦

1 and MM>

M≧

1, S being equal to C^a+C−

C(m)<sup>a−

1</sup> for C<

m, ‘

a’

being a first tuning parameter being set to a value>

0 and<

1, or S being equal to C^a+C−

C(M)<sup>a−

1</sup> for C>

M, or otherwise S being equal to C.

8. System according to claim 6, comprising means for the creation of an artificial reference speech signal, for which the noise levels as present in the original input speech signal are lowered by a scaling factor that depends on the local level of the noise in this input.

9. System according to claim 8, comprising means for setting the difference D(f)n in internal representations LX(f)n and LY(f)n resp. of said input signal (X) and output signal (Y) in the time-frequency plane to be equal to |LY(f)n−

LX(f)n^b/K<sup>b−

1</sup>| for LX(f)n<

K, or to be equal to |LY(f)n−

LX(f)n| for LX(f)n≧

K, b being a second tuning parameter being set to a value≧

1 and K being a low level noise power criterion value, representing a desired low level noise power criterion.

10. System according to claim 8, comprising means for setting a difference D(f)n in internal representations LX(f)n and LY(f)n resp. of said input signal (X) and output signal (Y) in the time-frequency plane to be equal to |LY(f)n−

LX(f)n^b/K<sup>b−

1</sup>| for LX(t)<

K′

or be equal to |LY(f)n−

LX(f)n| for LX(t)≧

K′

, b being a second tuning parameter being set to a value≧

1 and K′

being a low level noise power criterion value, representing the desired low level noise power criterion.