Sp-3-4350. 120-rv3 (to become ansi/tia-470. 120-C) Draft 22a ast ballot Comments with track changes on Telecommunications Telephone Terminal Equipment Transmission Requirements for Analog Speakerphones



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(Normative) – Noise Curves


The send and receive noise weighting curves are shown for reference.

    1. Send Noise Curves


Psophometric weighting is now being used for send noise measurements in the interest of harmonization with other standards. The psophometric weighting is defined in ITU-T Recommendation O.41 (94). The previously used C-message weighting (defined in IEEE Std 743-1995) is also shown for comparison purposes.

Table A.1 – Psophometric weighting curve Table A.2 – C-Message weighting curve

Frequency (Hz)

Relative weight (dB)

Tolerance ( dB)




Frequency (Hz)

Relative weight (dB)

Tolerance ( dB)

16.66

-85.0

–




60

-55.7

2

50

-63.0

2




100

-42.5

2

100

-41.0

2




200

-25.1

2

200

-21.0

2




300

-16.3

2

300

-10.6

1




400

-11.2

1

400

-6.3

1




500

-7.7

1

500

-3.6

1




600

-5.0

1

600

-2.0

1




700

-2.8

1

700

-0.9

1




800

-1.3

1

800

–0.0

0 (reference)




900

-0.3

1

900

0.6

1




1000

0.0

0 (reference)

1000

1.0

1




1200

-0.4

1

1200

–0.0

1




1300

-0.7

1

1400

-0.9

1




1500

-1.2

1

1600

-1.7

1




1800

-1.3

1

1800

-2.4

1




2000

-1.1

1

2000

-3.0

1




2500

-1.1

1

2500

-4.2

1




2800

-2.0

1

3000

-5.6

1




3000

-3.0

1

3500

-8.5

2




3300

-5.1

2

4000

-15.0

3




3500

-7.1

2

4500

-25.0

3




4000

-14.6

3

5000

-36.0

3




4500

-22.3

3

6000

-43.0

–




5000

> -28.7







Figure A.1 – Psophometric and C-Message noise weighting curves comparison


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